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Hitoshi Michibata - One of the best experts on this subject based on the ideXlab platform.
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Running title: Chloride Channel in Ascidian Vanadocytes
2015Co-Authors: Tatsuya Ueki, Nobuo Yamaguchi, Hitoshi MichibataAbstract:Ascidians, so-called sea squirts, can accumulate high levels of vanadium in the vacuoles of signet ring cells, which are one type of Ascidian blood cell and are also called vanadocytes. In addition to containing high concentrations of vanadium in the +3 oxidation state, the proton concentrations in vanadocyte vacuoles are extremely high. In order to elucidate the entire mechanism of the accumulation and reduction of vanadium by Ascidian vanadocytes, it is necessary to clarify the participation of anions, which might be involved as counter ions in the active accumulation of both vanadium and protons. We examined the chloride channel, since chloride ions are necessary for the acidification of intracellular vesicles and coexist with H+-ATPase. We cloned cDNA encoding a chloride channel from blood cells of a vanadium-rich Ascidian, Ascidia sydneiensis samea. It encoded a 787-amino-acid protein, which showed striking similarity to mammalian ClC3/4/5-type chloride channels. Using a whole-mount in situ hybridization method that we developed for Ascidian blood cells, the chloride channel was revealed to be transcribed in vanadocytes, suggesting its participation in the process of vanadium accumulation
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Identification of a Novel Vanadium-binding Protein by EST Analysis on the Most Vanadium-rich Ascidian, Ascidia gemmata
Marine Biotechnology, 2012Co-Authors: Setijono Samino, Hitoshi Michibata, Tatsuya UekiAbstract:Ascidians are known to accumulate extremely high levels of vanadium in their blood cells (up to 350 mM). The branchial sac and the intestine are thought to be the first tissues to contact the outer environment and absorb vanadium ions. The concentration of vanadium in the branchial sac and the intestine of the most vanadium-rich Ascidian Ascidia gemmata were determined to be 32.4 and 11.9 mM, respectively. Using an expressed sequence tag (EST) analysis of a cDNA library from the intestine of A. gemmata , we determined 960 ESTs and found 55 clones of metal-related gene orthologs, 6 redox-related orthologs, and 18 membrane transporter orthologs. Among them, two genes, which exhibited significant similarity to the vanadium-binding proteins of other vanadium-rich Ascidian species, were designated AgVanabin1 and AgVanabin2. Immobilized metal ion affinity chromatography revealed that recombinant AgVanabin1 bound to metal ions with an increasing affinity for Cu(II) > Zn(II) > Co(II) and AgVanabin2 bound to metal ions with an increasing affinity for Cu(II) > Fe(III) > V(IV). To examine the use of AgVanabins for a metal absorption system, we constructed Escherichia coli strains that expressed AgVanabin1 or AgVanabin2 fused to maltose-binding protein and secreted into the periplasmic space. We found that the strain expressing AgVanabin2 accumulated about 13.5 times more Cu(II) ions than the control TB1 strain. Significant accumulation of vanadium was also observed in the AgVanabin2-expressing strain as seen by a 1.5-fold increase.
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Identification and biochemical analysis of a homolog of a sulfate transporter from a vanadium-rich Ascidian Ascidia sydneiensis samea.
Biochimica et biophysica acta, 2009Co-Authors: Tatsuya Ueki, Kan Kanamori, Nobuaki Furuno, Yuya Nitta, Hitoshi MichibataAbstract:Abstract Background Several species of Ascidians accumulate extremely high levels of vanadium ions in the vacuoles of their blood cells (vanadocytes). The vacuoles of vanadocytes also contain many protons and sulfate ions. To maintain the concentration of sulfate ions, an active transporter must exist in the blood cells, but no such transporter has been reported in vanadium-accumulating Ascidians. Methods We determined the concentration of vanadium and sulfate ions in the blood cells (except for the giant cells) of Ascidia sydneiensis samea. We cloned cDNA for an Slc13-type sulfate transporter, AsSUL1, expressed in the vanadocytes of A. sydneiensis samea. The synthetic mRNA of AsSUL1 was introduced into Xenopus oocytes, and its ability to transport sulfate ions was analyzed. Results The concentrations of vanadium and sulfate ions in the blood cells (except for the giant cells) were 38 mM and 86 mM, respectively. The concentration of sulfate ions in the blood plasma was 25 mM. The transport activity of AsSUL1 was dependent on sodium ions, and its maximum velocity and apparent affinity were 2500 pmol/oocyte/h and 1.75 mM, respectively. General significance This could account for active uptake of sulfate ions from blood plasma where sulfate concentration is 25 mM, as determined in this study.
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Sequence variation of Vanabin2-like vanadium-binding proteins in blood cells of the vanadium-accumulating Ascidian Ascidia sydneiensis samea.
Biochimica et biophysica acta, 2008Co-Authors: Tatsuya Ueki, Kei Kamino, Makoto Satake, Hitoshi MichibataAbstract:The blood cells of Ascidians accumulate extremely high levels of the transition metal vanadium. We previously isolated four vanadium-binding proteins (Vanabins 1-4) and a homologous protein (VanabinP) from the vanadium-rich Ascidian Ascidia sydneiensis samea. In the present study, we identified cDNAs encoding five different Vanabin2-related proteins in A. sydneiensis samea blood cells. It was notable that the sequences of the encoded proteins vary from that of Vanabin2 at up to 14 specific positions, while both the polypeptide length and the 18 cysteine residues were completely conserved. The most divergent protein, named 14MT, differed from Vanabin2 at all 14 positions. Using immobilized metal-ion affinity chromatography, we found that Vanabin2 and 14MT have the same metal-ion selectivity, but the overall affinity of 14MT for VO(2+) is higher than that of Vanabin2. Binding number for VO(2+) ions was the same between Vanabin2 and 14MT as assessed by gel filtration. These results suggested that sequence variations were under strict evolutionary constraints and high-affinity binding sites for VO(2+) are conserved among Vanabin2 variants.
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Characterization of a novel vanadium-binding protein (VBP-129) from blood plasma of the vanadium-rich Ascidian Ascidia sydneiensis samea.
Biochimica et biophysica acta, 2007Co-Authors: Masao Yoshihara, Tatsuya Ueki, Nobuo Yamaguchi, Kei Kamino, Hitoshi MichibataAbstract:Abstract The Ascidians, the so-called sea squirts, accumulate high levels of vanadium, a transition metal. Since Henze first observed this physiologically unusual phenomenon about one hundred years ago, it has attracted interdisciplinary attention from chemists, physiologists, and biochemists. The maximum concentration of vanadium in Ascidians can reach 350 mM, and most of the vanadium ions are stored in the + 3 oxidation state in the vacuoles of vanadium-accumulating blood cells known as vanadocytes. Many proteins involved in the accumulation and reduction of vanadium in the vanadocytes, blood plasma, and digestive tract have been identified. However, the process by which vanadium is taken in prior to its accumulation in vanadocytes has not been elucidated. In the present study, a novel vanadium-binding protein, designated VBP-129, was identified from blood plasma of the vanadium-rich Ascidian Ascidia sydneiensis samea . Although VBP-129 mRNA was transcribed in all A. sydneiensis samea tissues examined, the VBP-129 protein was exclusively localized in blood plasma and muscle cells of this Ascidian. It bound not only to VO 2+ but also to Fe 3+ , Co 2+ , Cu 2+ , and Zn 2+ ; on the other hand, a truncated form of VBP-129, designated VBP-88, bound only to Co 2+ , Cu 2+ and Zn 2+ . In a pull-down assay, an interaction between VanabinP and VBP-129 occurred both in the presence and the absence of VO 2+ . These results suggest that VBP-129 and VanabinP function cooperatively as metallochaperones in blood plasma.
Tatsuya Ueki - One of the best experts on this subject based on the ideXlab platform.
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Bioaccumulation of Vanadium by Vanadium-Resistant Bacteria Isolated from the Intestine of Ascidia sydneiensis samea
Marine Biotechnology, 2016Co-Authors: Tatsuya UekiAbstract:Isolation of naturally occurring bacterial strains from metal-rich environments has gained popularity due to the growing need for bioremediation technologies. In this study, we found that the vanadium concentration in the intestine of the vanadium-rich Ascidian Ascidia sydneiensis samea could reach 0.67 mM, and thus, we isolated vanadium-resistant bacteria from the intestinal contents and determined the ability of each bacterial strain to accumulate vanadium and other heavy metals. Nine strains of vanadium-resistant bacteria were successfully isolated, of which two strains, V-RA-4 and S-RA-6, accumulated vanadium at a higher rate than did the other strains. The maximum vanadium absorption by these bacteria was achieved at pH 3, and intracellular accumulation was the predominant mechanism. Each strain strongly accumulated copper and cobalt ions, but accumulation of nickel and molybdate ions was relatively low. These bacterial strains can be applied to protocols for bioremediation of vanadium and heavy metal toxicity.
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Running title: Chloride Channel in Ascidian Vanadocytes
2015Co-Authors: Tatsuya Ueki, Nobuo Yamaguchi, Hitoshi MichibataAbstract:Ascidians, so-called sea squirts, can accumulate high levels of vanadium in the vacuoles of signet ring cells, which are one type of Ascidian blood cell and are also called vanadocytes. In addition to containing high concentrations of vanadium in the +3 oxidation state, the proton concentrations in vanadocyte vacuoles are extremely high. In order to elucidate the entire mechanism of the accumulation and reduction of vanadium by Ascidian vanadocytes, it is necessary to clarify the participation of anions, which might be involved as counter ions in the active accumulation of both vanadium and protons. We examined the chloride channel, since chloride ions are necessary for the acidification of intracellular vesicles and coexist with H+-ATPase. We cloned cDNA encoding a chloride channel from blood cells of a vanadium-rich Ascidian, Ascidia sydneiensis samea. It encoded a 787-amino-acid protein, which showed striking similarity to mammalian ClC3/4/5-type chloride channels. Using a whole-mount in situ hybridization method that we developed for Ascidian blood cells, the chloride channel was revealed to be transcribed in vanadocytes, suggesting its participation in the process of vanadium accumulation
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Identification of a Novel Vanadium-binding Protein by EST Analysis on the Most Vanadium-rich Ascidian, Ascidia gemmata
Marine Biotechnology, 2012Co-Authors: Setijono Samino, Hitoshi Michibata, Tatsuya UekiAbstract:Ascidians are known to accumulate extremely high levels of vanadium in their blood cells (up to 350 mM). The branchial sac and the intestine are thought to be the first tissues to contact the outer environment and absorb vanadium ions. The concentration of vanadium in the branchial sac and the intestine of the most vanadium-rich Ascidian Ascidia gemmata were determined to be 32.4 and 11.9 mM, respectively. Using an expressed sequence tag (EST) analysis of a cDNA library from the intestine of A. gemmata , we determined 960 ESTs and found 55 clones of metal-related gene orthologs, 6 redox-related orthologs, and 18 membrane transporter orthologs. Among them, two genes, which exhibited significant similarity to the vanadium-binding proteins of other vanadium-rich Ascidian species, were designated AgVanabin1 and AgVanabin2. Immobilized metal ion affinity chromatography revealed that recombinant AgVanabin1 bound to metal ions with an increasing affinity for Cu(II) > Zn(II) > Co(II) and AgVanabin2 bound to metal ions with an increasing affinity for Cu(II) > Fe(III) > V(IV). To examine the use of AgVanabins for a metal absorption system, we constructed Escherichia coli strains that expressed AgVanabin1 or AgVanabin2 fused to maltose-binding protein and secreted into the periplasmic space. We found that the strain expressing AgVanabin2 accumulated about 13.5 times more Cu(II) ions than the control TB1 strain. Significant accumulation of vanadium was also observed in the AgVanabin2-expressing strain as seen by a 1.5-fold increase.
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Identification and biochemical analysis of a homolog of a sulfate transporter from a vanadium-rich Ascidian Ascidia sydneiensis samea.
Biochimica et biophysica acta, 2009Co-Authors: Tatsuya Ueki, Kan Kanamori, Nobuaki Furuno, Yuya Nitta, Hitoshi MichibataAbstract:Abstract Background Several species of Ascidians accumulate extremely high levels of vanadium ions in the vacuoles of their blood cells (vanadocytes). The vacuoles of vanadocytes also contain many protons and sulfate ions. To maintain the concentration of sulfate ions, an active transporter must exist in the blood cells, but no such transporter has been reported in vanadium-accumulating Ascidians. Methods We determined the concentration of vanadium and sulfate ions in the blood cells (except for the giant cells) of Ascidia sydneiensis samea. We cloned cDNA for an Slc13-type sulfate transporter, AsSUL1, expressed in the vanadocytes of A. sydneiensis samea. The synthetic mRNA of AsSUL1 was introduced into Xenopus oocytes, and its ability to transport sulfate ions was analyzed. Results The concentrations of vanadium and sulfate ions in the blood cells (except for the giant cells) were 38 mM and 86 mM, respectively. The concentration of sulfate ions in the blood plasma was 25 mM. The transport activity of AsSUL1 was dependent on sodium ions, and its maximum velocity and apparent affinity were 2500 pmol/oocyte/h and 1.75 mM, respectively. General significance This could account for active uptake of sulfate ions from blood plasma where sulfate concentration is 25 mM, as determined in this study.
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Sequence variation of Vanabin2-like vanadium-binding proteins in blood cells of the vanadium-accumulating Ascidian Ascidia sydneiensis samea.
Biochimica et biophysica acta, 2008Co-Authors: Tatsuya Ueki, Kei Kamino, Makoto Satake, Hitoshi MichibataAbstract:The blood cells of Ascidians accumulate extremely high levels of the transition metal vanadium. We previously isolated four vanadium-binding proteins (Vanabins 1-4) and a homologous protein (VanabinP) from the vanadium-rich Ascidian Ascidia sydneiensis samea. In the present study, we identified cDNAs encoding five different Vanabin2-related proteins in A. sydneiensis samea blood cells. It was notable that the sequences of the encoded proteins vary from that of Vanabin2 at up to 14 specific positions, while both the polypeptide length and the 18 cysteine residues were completely conserved. The most divergent protein, named 14MT, differed from Vanabin2 at all 14 positions. Using immobilized metal-ion affinity chromatography, we found that Vanabin2 and 14MT have the same metal-ion selectivity, but the overall affinity of 14MT for VO(2+) is higher than that of Vanabin2. Binding number for VO(2+) ions was the same between Vanabin2 and 14MT as assessed by gel filtration. These results suggested that sequence variations were under strict evolutionary constraints and high-affinity binding sites for VO(2+) are conserved among Vanabin2 variants.
Nobuo Yamaguchi - One of the best experts on this subject based on the ideXlab platform.
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Running title: Chloride Channel in Ascidian Vanadocytes
2015Co-Authors: Tatsuya Ueki, Nobuo Yamaguchi, Hitoshi MichibataAbstract:Ascidians, so-called sea squirts, can accumulate high levels of vanadium in the vacuoles of signet ring cells, which are one type of Ascidian blood cell and are also called vanadocytes. In addition to containing high concentrations of vanadium in the +3 oxidation state, the proton concentrations in vanadocyte vacuoles are extremely high. In order to elucidate the entire mechanism of the accumulation and reduction of vanadium by Ascidian vanadocytes, it is necessary to clarify the participation of anions, which might be involved as counter ions in the active accumulation of both vanadium and protons. We examined the chloride channel, since chloride ions are necessary for the acidification of intracellular vesicles and coexist with H+-ATPase. We cloned cDNA encoding a chloride channel from blood cells of a vanadium-rich Ascidian, Ascidia sydneiensis samea. It encoded a 787-amino-acid protein, which showed striking similarity to mammalian ClC3/4/5-type chloride channels. Using a whole-mount in situ hybridization method that we developed for Ascidian blood cells, the chloride channel was revealed to be transcribed in vanadocytes, suggesting its participation in the process of vanadium accumulation
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Characterization of a novel vanadium-binding protein (VBP-129) from blood plasma of the vanadium-rich Ascidian Ascidia sydneiensis samea.
Biochimica et biophysica acta, 2007Co-Authors: Masao Yoshihara, Tatsuya Ueki, Nobuo Yamaguchi, Kei Kamino, Hitoshi MichibataAbstract:Abstract The Ascidians, the so-called sea squirts, accumulate high levels of vanadium, a transition metal. Since Henze first observed this physiologically unusual phenomenon about one hundred years ago, it has attracted interdisciplinary attention from chemists, physiologists, and biochemists. The maximum concentration of vanadium in Ascidians can reach 350 mM, and most of the vanadium ions are stored in the + 3 oxidation state in the vacuoles of vanadium-accumulating blood cells known as vanadocytes. Many proteins involved in the accumulation and reduction of vanadium in the vanadocytes, blood plasma, and digestive tract have been identified. However, the process by which vanadium is taken in prior to its accumulation in vanadocytes has not been elucidated. In the present study, a novel vanadium-binding protein, designated VBP-129, was identified from blood plasma of the vanadium-rich Ascidian Ascidia sydneiensis samea . Although VBP-129 mRNA was transcribed in all A. sydneiensis samea tissues examined, the VBP-129 protein was exclusively localized in blood plasma and muscle cells of this Ascidian. It bound not only to VO 2+ but also to Fe 3+ , Co 2+ , Cu 2+ , and Zn 2+ ; on the other hand, a truncated form of VBP-129, designated VBP-88, bound only to Co 2+ , Cu 2+ and Zn 2+ . In a pull-down assay, an interaction between VanabinP and VBP-129 occurred both in the presence and the absence of VO 2+ . These results suggest that VBP-129 and VanabinP function cooperatively as metallochaperones in blood plasma.
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Glutathione transferases with vanadium-binding activity isolated from the vanadium-rich Ascidian Ascidia sydneiensis samea
Biochimica et biophysica acta, 2006Co-Authors: Masafumi Yoshinaga, Tatsuya Ueki, Nobuo Yamaguchi, Kei Kamino, Hitoshi MichibataAbstract:Some Ascidians accumulate vanadium in vanadocytes, which are vanadium-containing blood cells, at high levels and with high selectivity. However, the mechanism and physiological significance of vanadium accumulation remain unknown. In this study, we isolated novel proteins with a striking homology to glutathione transferases (GSTs), designated AsGST-I and AsGST-II, from the digestive system of the vanadium-accumulating Ascidian Ascidia sydneiensis samea, in which the digestive system is thought to be involved in vanadium uptake. Analysis of recombinant AsGST-I confirmed that AsGST-I has GST activity and forms a dimer, as do other GSTs. In addition, AsGST-I was revealed to have vanadium-binding activity, which has never been reported for GSTs isolated from other organisms. AsGST-I bound about 16 vanadium atoms as either V(IV) or V(V) per dimer, and the apparent dissociation constants for V(IV) and V(V) were 1.8 x 10(-4) M and 1.2 x 10(-4) M, respectively. Western blot analysis revealed that AsGSTs were expressed in the digestive system at exceptionally high levels, although they were localized in almost all organs and tissues examined. Considering these results, we postulate that AsGSTs play important roles in vanadium accumulation in the Ascidian digestive system.
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Localization of Vanabins, Vanadium-Binding Proteins, in the Blood Cells of the Vanadium-Rich Ascidian, Ascidia sydneiensis samea
Zoological science, 2006Co-Authors: Nobuo Yamaguchi, Tatsuya Ueki, Yuko Amakawa, Hiroshi Yamada, Hitoshi MichibataAbstract:Abstract Some species of the family Ascidiidae accumulate vanadium in concentrations in excess of 350 mM, which is about 107-fold higher than the concentration of vanadium in seawater. In these species, signet ring cells with a single large vacuole in which vanadium ions are contained function as vanadium-accumulating cells. These have been termed vanadocytes. We recently isolated five vanadium-binding proteins, which we named Vanabin1, Vanabin2, Vanabin3, Vanabin4, and VanabinP, from vanadocytes of the vanadium-rich Ascidian Ascidia sydneiensis samea. In this study, we analyzed localization of the Vanabins in the blood cells of A. sydneiensis samea using monoclonal antibodies and confocal microscopy. The Vanabin1 and Vanabin2 proteins were found in the cytoplasm and/or in some organelles of vanadocytes. Vanabin3 was also detected in the cytoplasm, while Vanabin4 was found exclusively in the cytoplasmic membrane.
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VanabinP, a novel vanadium-binding protein in the blood plasma of an Ascidian, Ascidia sydneiensis samea.
Biochimica et biophysica acta, 2005Co-Authors: Masao Yoshihara, Tatsuya Ueki, Nobuo Yamaguchi, Kei Kamino, Takahiro Watanabe, Hitoshi MichibataAbstract:Abstract Some Ascidians accumulate high levels of the transition metal vanadium in their blood cells. The process of vanadium accumulation has not yet been elucidated. In this report, we describe the isolation and cDNA cloning of a novel vanadium-binding protein, designated as VanabinP, from the blood plasma of the vanadium-rich Ascidian, Ascidia sydneiensis samea . The predicted amino acid sequence of VanabinP was highly conserved and similar to those of other Vanabins. The N-terminus of the mature form of VanabinP was rich in basic amino acid residues. VanabinP cDNA was originally isolated from blood cells, as were the other four Vanabins. However, Western blot analysis revealed that the VanabinP protein was localized to the blood plasma and was not detectable in blood cells. RT-PCR analysis and in situ hybridization indicated that the VanabinP gene was transcribed in some cell types localized to peripheral connective tissues of the alimentary canal, muscle, blood cells, and a portion of the branchial sac. Recombinant VanabinP bound a maximum of 13 vanadium(IV) ions per molecule with a K d of 2.8 × 10 −5 M. These results suggest that VanabinP is produced in several types of cell, including blood cells, and is immediately secreted into the blood plasma where it functions as a vanadium(IV) carrier.
Mercier Annie - One of the best experts on this subject based on the ideXlab platform.
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The life history and feeding ecology of velvet shell, Velutina velutina (Gastropoda: Velutinidae), a specialist predator of Ascidians
NRC Research Press (a division of Canadian Science Publishing), 2019Co-Authors: Sargent Philip, Hamel Jean-francois, Mercier AnnieAbstract:Velvet shell, Velutina velutina (Müller, 1776), is a specialist predator of Ascidians, like other members of the gastropod family Velutinidae. Globally, invasive Ascidians have become problematic, ecologically and economically, yet ecological knowledge of velutinids remains limited. This study outlines the life history and feeding ecology of V. velutina in eastern Canada based on laboratory work complemented by field observations. The life history of V. velutina is closely linked with Ascidians, which serve as prey and protection for their egg capsules. Egg capsules were embedded within tunics of Aplidium glabrum (Verrill, 1871) and Ascidia callosa Stimpson, 1852, with a preference for the latter. Seasonal behavioural shifts were consistent annually and corresponded with seawater temperature cycles. Feeding dominated during the coldest months (January–May), growth occurred as water temperature increased to the annual maximum (June and July), transitioning to mating during the warmest period (July–August), and egg capsule deposition dominated as water temperature declined (November–January). Larvae hatched between January and July after 2–4 months of development. Velutina velutina preyed on all Ascidian species presented during this study, including golden star tunicate, Botryllus schlosseri (Pallas, 1766), and vase tunicate, Ciona intestinalis (Linnaeus, 1767), two non-indigenous species, although solitary species were preferred.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
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The life history and feeding ecology of velvet shell, Velutina velutina (Gastropoda: Velutinidae), a specialist predator of Ascidians
'Canadian Science Publishing', 2019Co-Authors: Sargent Philip, Hamel Jean-francois, Mercier AnnieAbstract:Velvet shell, Velutina velutina (O. F. Müller, 1776), is a specialist predator of Ascidians, like other members of the gastropod family Velutinidae. Globally, invasive Ascidians have become problematic, ecologically and economically, yet ecological knowledge of velutinids remains limited. This study outlines the life history and feeding ecology of V. velutina in eastern Canada based on laboratory work complemented by field observations. The life history of V. velutina is closely linked with Ascidians, which serve as prey and protection for their egg capsules. Egg capsules were embedded within tunics of Aplidium glabrum (Verrill, 1871) and Ascidia callosa Stimpson, 1852, but the latter was preferred. Seasonal behavioural shifts were consistent annually and corresponded with seawater temperature cycles. Feeding dominated during the coldest months (January – May), growth occurred as water temperature increased to the annual maximum (June and July), transitioned to mating during the warmest period (July/August), and egg capsule deposition dominated as water temperature declined (November – January). Larvae hatched between January and July after 2 – 4 months of development. Velvet shell preyed on all Ascidian species presented during this study, including golden star tunicate, Botryllus schlosseri (Pallas, 1766), and vase tunicate, Ciona intestinalis (Linnaeus, 1767), two non-indigenous species, although solitary species were preferred
Kei Kamino - One of the best experts on this subject based on the ideXlab platform.
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Sequence variation of Vanabin2-like vanadium-binding proteins in blood cells of the vanadium-accumulating Ascidian Ascidia sydneiensis samea.
Biochimica et biophysica acta, 2008Co-Authors: Tatsuya Ueki, Kei Kamino, Makoto Satake, Hitoshi MichibataAbstract:The blood cells of Ascidians accumulate extremely high levels of the transition metal vanadium. We previously isolated four vanadium-binding proteins (Vanabins 1-4) and a homologous protein (VanabinP) from the vanadium-rich Ascidian Ascidia sydneiensis samea. In the present study, we identified cDNAs encoding five different Vanabin2-related proteins in A. sydneiensis samea blood cells. It was notable that the sequences of the encoded proteins vary from that of Vanabin2 at up to 14 specific positions, while both the polypeptide length and the 18 cysteine residues were completely conserved. The most divergent protein, named 14MT, differed from Vanabin2 at all 14 positions. Using immobilized metal-ion affinity chromatography, we found that Vanabin2 and 14MT have the same metal-ion selectivity, but the overall affinity of 14MT for VO(2+) is higher than that of Vanabin2. Binding number for VO(2+) ions was the same between Vanabin2 and 14MT as assessed by gel filtration. These results suggested that sequence variations were under strict evolutionary constraints and high-affinity binding sites for VO(2+) are conserved among Vanabin2 variants.
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Characterization of a novel vanadium-binding protein (VBP-129) from blood plasma of the vanadium-rich Ascidian Ascidia sydneiensis samea.
Biochimica et biophysica acta, 2007Co-Authors: Masao Yoshihara, Tatsuya Ueki, Nobuo Yamaguchi, Kei Kamino, Hitoshi MichibataAbstract:Abstract The Ascidians, the so-called sea squirts, accumulate high levels of vanadium, a transition metal. Since Henze first observed this physiologically unusual phenomenon about one hundred years ago, it has attracted interdisciplinary attention from chemists, physiologists, and biochemists. The maximum concentration of vanadium in Ascidians can reach 350 mM, and most of the vanadium ions are stored in the + 3 oxidation state in the vacuoles of vanadium-accumulating blood cells known as vanadocytes. Many proteins involved in the accumulation and reduction of vanadium in the vanadocytes, blood plasma, and digestive tract have been identified. However, the process by which vanadium is taken in prior to its accumulation in vanadocytes has not been elucidated. In the present study, a novel vanadium-binding protein, designated VBP-129, was identified from blood plasma of the vanadium-rich Ascidian Ascidia sydneiensis samea . Although VBP-129 mRNA was transcribed in all A. sydneiensis samea tissues examined, the VBP-129 protein was exclusively localized in blood plasma and muscle cells of this Ascidian. It bound not only to VO 2+ but also to Fe 3+ , Co 2+ , Cu 2+ , and Zn 2+ ; on the other hand, a truncated form of VBP-129, designated VBP-88, bound only to Co 2+ , Cu 2+ and Zn 2+ . In a pull-down assay, an interaction between VanabinP and VBP-129 occurred both in the presence and the absence of VO 2+ . These results suggest that VBP-129 and VanabinP function cooperatively as metallochaperones in blood plasma.
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Glutathione transferases with vanadium-binding activity isolated from the vanadium-rich Ascidian Ascidia sydneiensis samea
Biochimica et biophysica acta, 2006Co-Authors: Masafumi Yoshinaga, Tatsuya Ueki, Nobuo Yamaguchi, Kei Kamino, Hitoshi MichibataAbstract:Some Ascidians accumulate vanadium in vanadocytes, which are vanadium-containing blood cells, at high levels and with high selectivity. However, the mechanism and physiological significance of vanadium accumulation remain unknown. In this study, we isolated novel proteins with a striking homology to glutathione transferases (GSTs), designated AsGST-I and AsGST-II, from the digestive system of the vanadium-accumulating Ascidian Ascidia sydneiensis samea, in which the digestive system is thought to be involved in vanadium uptake. Analysis of recombinant AsGST-I confirmed that AsGST-I has GST activity and forms a dimer, as do other GSTs. In addition, AsGST-I was revealed to have vanadium-binding activity, which has never been reported for GSTs isolated from other organisms. AsGST-I bound about 16 vanadium atoms as either V(IV) or V(V) per dimer, and the apparent dissociation constants for V(IV) and V(V) were 1.8 x 10(-4) M and 1.2 x 10(-4) M, respectively. Western blot analysis revealed that AsGSTs were expressed in the digestive system at exceptionally high levels, although they were localized in almost all organs and tissues examined. Considering these results, we postulate that AsGSTs play important roles in vanadium accumulation in the Ascidian digestive system.
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VanabinP, a novel vanadium-binding protein in the blood plasma of an Ascidian, Ascidia sydneiensis samea.
Biochimica et biophysica acta, 2005Co-Authors: Masao Yoshihara, Tatsuya Ueki, Nobuo Yamaguchi, Kei Kamino, Takahiro Watanabe, Hitoshi MichibataAbstract:Abstract Some Ascidians accumulate high levels of the transition metal vanadium in their blood cells. The process of vanadium accumulation has not yet been elucidated. In this report, we describe the isolation and cDNA cloning of a novel vanadium-binding protein, designated as VanabinP, from the blood plasma of the vanadium-rich Ascidian, Ascidia sydneiensis samea . The predicted amino acid sequence of VanabinP was highly conserved and similar to those of other Vanabins. The N-terminus of the mature form of VanabinP was rich in basic amino acid residues. VanabinP cDNA was originally isolated from blood cells, as were the other four Vanabins. However, Western blot analysis revealed that the VanabinP protein was localized to the blood plasma and was not detectable in blood cells. RT-PCR analysis and in situ hybridization indicated that the VanabinP gene was transcribed in some cell types localized to peripheral connective tissues of the alimentary canal, muscle, blood cells, and a portion of the branchial sac. Recombinant VanabinP bound a maximum of 13 vanadium(IV) ions per molecule with a K d of 2.8 × 10 −5 M. These results suggest that VanabinP is produced in several types of cell, including blood cells, and is immediately secreted into the blood plasma where it functions as a vanadium(IV) carrier.
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Expressed Sequence Tag Analysis of Vanadocytes in a Vanadium-Rich Ascidian, Ascidia sydneiensis samea
Marine Biotechnology, 2004Co-Authors: Nobuo Yamaguchi, Tatsuya Ueki, Kei Kamino, Hitoshi MichibataAbstract:Some species in the family Ascidiidae accumulate vanadium at concentrations in excess of 350 mM, which corresponds to about 10^7 times higher than that in seawater. In these species signet ring cells, with a single huge vacuole in which vanadium ion is contained, function as vanadium-accumulating cells, vanadocytes. To investigate the mechanism underlying this phenomenon, we performed an expressed sequence tag (EST) analysis of a complementary DNA library from vanadocytes of a vanadium-rich Ascidian, Ascidia sydneiensis samea. We determined the nucleotide sequences of 1000 ESTs and performed a BLAST analysis against the SwissProt database. We found 93 clones of metal-related gene homologues, including the ferritin heavy subunit, hemocyanin, and metallothionein. Two ESTs, in particular, exhibited significant similarity to vanabins that have been extracted from A. sydneiensis samea blood cells as low molecular weight vanadium-binding proteins. We have named the genes encoding these ESTs vanabin3 and vanabin4. Immobilized metal ion affinity chromatography revealed that these novel vanabin homologues bind vanadium(IV) ions.
