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Thorsten Burmester - One of the best experts on this subject based on the ideXlab platform.
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Expression and evolution of Hexamerins from the tobacco hornworm, Manduca sexta, and other Lepidoptera.
Insect biochemistry and molecular biology, 2014Co-Authors: Thorsten BurmesterAbstract:Hexamerins are large hemolymph-proteins that accumulate during the late larval stages of insects. Hexamerins have emerged from hemocyanin, but have lost the ability to bind oxygen. Hexamerins are mainly considered as storage proteins for non-feeding stages, but may also have other functions, e.g. in cuticle formation, transport and immune response. The genome of the hornworm Manduca sexta harbors six hexamerin genes. Two of them code for arylphorins (Msex2.01690, Msex2.15504) and two genes correspond to a methionine-rich hexamerin (Msex2.10735) and a moderately methionine-rich hexamerin (Msex2.01694), respectively. Two other genes do not correspond to any known hexamerin and distantly resemble the arylphorins (Msex2.01691, Msex2.01693). Five of the six hexamerin genes are clustered within ∼45 kb on scaffold 00023, which shows conserved synteny in various lepidopteran genomes. The methionine-rich hexamerin gene is located at a distinct site. M. sexta and other Lepidoptera have lost the riboflavin-binding hexamerin. With the exception of Msex2.01691, which displays low mRNA levels throughout the life cycle, all Hexamerins are most highly expressed during pre-wandering phase of the 5th larval instar of M. sexta, supporting their role as storage proteins. Notably, Msex2.01691 is most highly expressed in the brain, suggesting a divergent function. Phylogenetic analyses showed that hexamerin evolution basically follows insect systematics. Lepidoptera display an unparalleled diversity of Hexamerins, which exceeds that of other hexapod orders. In contrast to previous analyses, the lepidopteran Hexamerins were found monophyletic. Five distinct types of Hexamerins have been identified in this order, which differ in terms of amino acid composition and evolutionary history: i. the arylphorins, which are rich in aromatic amino acids (∼20% phenylalanine and tyrosine), ii. the distantly related arylphorin-like Hexamerins, iii. the methionine-rich Hexamerins, iv. the moderately methionine rich Hexamerins, and v. the riboflavin-binding Hexamerins.
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Evolution and function of the insect Hexamerins
European Journal of Entomology, 2013Co-Authors: Thorsten BurmesterAbstract:Hexamerins are hemocyanin-related haemolymph proteins that are widespread in insects and may accumulate to extraordinarily high concentrations in larval stages. Hexamerins were originally described as storage proteins that provide amino acids and energy for non-feeding periods. However, in recent years other specific functions like cuticle formation, transport of hormones and other organic compounds, or humoral immune defense have been proposed. During evolution, Hexamerins diversified according to the divergence of the insect orders. Within the orders, there is a notable structural diversification of these proteins, which probably reflects specific functions. In this paper, the different possible roles of the Hexamerins are reviewed and discussed in the context of hexamerin phylogeny.
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A putative hexamerin from a Campodea sp. suggests an independent origin of haemocyanin-related storage proteins in Hexapoda.
Insect molecular biology, 2009Co-Authors: Christian Pick, Thorsten BurmesterAbstract:Haemocyanins are copper-containing respiratory proteins in the arthropod haemolymph. In hexapods, haemocyanins gave rise to Hexamerins, which have lost the ability to bind copper and thus oxygen. Hexamerins are thought to act mainly as storage proteins in nonfeeding periods. So far, Hexamerins have only been identified in ectognathan hexapods, but not in Entognatha. Here we report the identification of a putative hexamerin from Campodea sp. (Diplura). The full-length cDNA of Campodea sp. hexamerin 1 (CspHex1) measures 2188 bp and translates into a native polypeptide of 667 amino acids. As in other Hexamerins, the six copper-coordinating histidines are not conserved. However, sequence comparison and phylogenetic analyses demonstrated that CspHex1 is not closely related to other hexapod Hexamerins, which derive from hexapod type 1 haemocyanin subunits in the ectognathan lineage, but rather resembles a derivative of hexapod type 2 haemocyanin subunits. Hence, haemocyanin-related storage proteins emerged at least two times independently in Hexapoda.
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Molecular characterization of hemocyanin and hexamerin from the firebrat Thermobia domestica (Zygentoma)
Insect biochemistry and molecular biology, 2008Co-Authors: Christian Pick, Silke Hagner-holler, Thorsten BurmesterAbstract:Hexapods possess a tracheal system that enables the transport of oxygen to the inner organs. Although respiratory proteins have been considered unnecessary in most Hexapoda for this reason, we recently showed the presence of a functional hemocyanin in the stonefly Perla marginata. Here we report the identification and molecular characterization of a hemocyanin from Zygentoma (Thysanura). We obtained the full length cDNA of two distinct subunit types from the firebrat Thermobia domestica, and partial sequences of the orthologs from the silverfish Lepisma saccharina. The native T. domestica hemocyanin subunits both consist of 658 amino acids, but a signal peptide for transmembrane transport is missing in subunit 2. In adult firebrats both hemocyanin subunits represent a substantial proportion of the total hemolymph proteins. Phylogenetic analyses show that the subunit types are orthologous to subunits 1 and 2 of the stonefly Perla marginata. We further identified and sequenced a hexamerin subunit from T. domestica (689 amino acids), which suggests an early emergence of this type of proteins in hexapod evolution. In contrast to most other Hexamerins, it does not reveal a high content in phenylalanine and tyrosine, which may be interpreted that the accumulation of aromatic amino acids commenced later in hexamerin evolution. Molecular clock calculations using Hexamerins suggest that the divergence of Zygentoma and Pterygota occurred around 387 million years ago, which is in excellent agreement with the available fossil record.
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Evolutionary history and diversity of arthropod hemocyanins.
Micron (Oxford England : 1993), 2004Co-Authors: Thorsten BurmesterAbstract:Hemocyanins are copper-containing, multi-subunit proteins that transport oxygen in the hemolymph of many molluscs and arthropods [Markl and Decher, Adv. Comp. Environ. Physiol. 13 (1992) 325; van Holde et al., J. Biol. Chem. 276 (2001) 15563]. Arthropod hemocyanins originated more than 550 million years ago from oxygen-consuming phenoloxidases. Hemocyanins are present in various Onychophora, Chelicerata, Myriapoda, Crustacea, and Hexapoda, but subunit evolution differs striking in these arthropod subphyla. Hemocyanins also gave rise to non-respiratory proteins (crustacean pseudo-hemocyanins, insect Hexamerins, and hexamerin receptors), which most likely have storage functions.
Diana E. Wheeler - One of the best experts on this subject based on the ideXlab platform.
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Presence of a single abundant storage hexamerin in both larvae and adults of the grasshopper, Schistocerca americana
Journal of insect physiology, 2003Co-Authors: Daniel A. Hahn, Diana E. WheelerAbstract:We identified a single hexameric storage protein in the grasshopper, Schistocerca americana, and monitored its abundance through the last larval instar and up until reproductive competence in adults of both sexes. This storage hexamerin, termed Schistocerca americana Persistent Storage Protein (saPSP) was the most abundant soluble protein in both larvae and adults. In both sexes, saPSP abundance started out low at the onset of the last larval instar and accumulated during feeding, peaking just prior to molting. Adults of both sexes contained significant amounts of saPSP after eclosion. In adult males, saPSP content dropped continuously after eclosion and was lowest once individuals reached reproductive maturity. In contrast, adult females depleted saPSP reserves during the first days of adulthood, but subsequently accumulated significant saPSP stores. In adult females, saPSP stores peaked just prior to the completion of egg provisioning. Given the overall patterns of abundance, saPSP has functions in both larvae and adults. In addition, the observed pattern of storage hexamerin accumulation differs from patterns of accumulation in the other known grasshoppers, Locusta migratoria and Romalea microptera, suggesting that significant functional diversity has evolved in storage Hexamerins among the grasshoppers.
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Storage proteins in vespid wasps: characterization, developmental pattern, and occurrence in adults
Journal of insect physiology, 2003Co-Authors: James H. Hunt, N. A. Buck, Diana E. WheelerAbstract:Wasps of family Vespidae contain three types of major proteins that have the size, amino acid composition, subunit composition, immunological reactivity, and pattern of occurrence characteristic of storage proteins. The three types of storage protein, which have been identified in other Hymenoptera, are very high density lipoprotein, high glutamine/glutamic acid protein, and hexamerin. The predominant pattern of occurrence for these proteins is as known from most or all Holometabola: synthesis during the last larval instar and utilization as an amino acid source during metamorphosis. Hexamerin also occurred in a large young adult female Monobia quadridens but not a small one, which suggests that carry-over into adult females is a reaction norm response to quantity of larval provisions, because these wasps could not have fed as adults. In two paper wasp species of the genus Polistes, hexamerin was present in large adult females which emerged during the colony cycle phase when reproductive females are typically produced, but not in adult female offspring that emerged earlier in the colony cycle or in adult females that were workers. It cannot be confirmed by these data that the hexamerin in the adult paper wasps represented carry-over from metamorphosis rather than post-emergence feeding, but the pattern of occurrence suggests that presence of storage protein may play a role in caste differentiation in paper wasps. No storage protein was found in any adult Vespula maculifrons, a yellowjacket wasp, suggesting that caste differentiation in vespine wasps does not incorporate storage protein as a component.
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Female-specific expression of a hexamerin gene in larvae of an autogenous mosquito.
European journal of biochemistry, 2001Co-Authors: Stanislav O. Zakharkin, Diana E. Wheeler, Violetta V. Headley, Nagothu K. Kumar, N. A. Buck, Helen BenešAbstract:Fourth-instar larvae of the autogenous mosquito, Aedes atropalpus, synthesize three Hexamerins or hexameric storage proteins which are distinguished by different methionine and aromatic amino-acid contents. One protein, Hexamerin-1.2 (AatHex-1.2) is only found in female larvae and pupae. In order to investigate the molecular basis for this sex-specific accumulation, we have cloned and sequenced the cDNA encoding AatHex-1.2 and isolated and sequenced over 1 kb of the 5′ flanking region of the AatHex-1.2 gene. The AatHex-1.2 transcript encodes a 81.6-kDa hexamerin subunit which contains 19.8% phenylalanine, tyrosine and tryptophan and 8.6% methionine residues. The single-copy AatHex-1.2 gene consists of three exons and two small introns located at its 5′ end. A 2.3-kb AatHex-1.2 mRNA accumulates only in female larvae and pupae and is expressed at very low levels in adult female mosquitoes. The temporal expression profile of this transcript is typical of other mosquito hexamerin genes, with rapid disappearance of the mRNA shortly after pupation. Hence this is the first observation of exclusively female-specific gene activity during preadult development of an insect. In the 5′ flanking region of the AatHex-1.2 gene, we identified putative binding sites for transcription factors, such as GATA, C/EBP and Doublesex, typically involved in fat body- and female-specific gene activity in Diptera. These findings suggest that mechanisms for sex-specific transcription in the fat body may be well conserved between flies and mosquitoes.
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Sequence and evolution of a hexamerin from the ant Camponotus festinatus
Insect molecular biology, 2000Co-Authors: Teresa Martinez, Thorsten Burmester, Jan A. Veenstra, Diana E. WheelerAbstract:In the ant Camponotus festinatus, two different Hexamerins accumulate stage-specifically during the late larval period and at various times in adults. These Hexamerins serve as storage proteins and play important roles in brood nourishment and colony founding. We report an analysis of the cDNA sequence of C. festinatus hexamerin 2 (CfeHex2). The native protein contains 732 amino acids, which are moderately enriched in aromatic amino acids, aspartate and asparagine. Phylogenetic analyses show a close relationship of CfeHex2 to a putative toxin of the braconid wasp, Bracon hebetor. The divergence of Formicidae and Braconidae Hexamerins was calculated to have begun 187 MYA, an estimate consistent with currently accepted phylogeny of insect orders.
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Storage proteins in ants (Hymenoptera:Formicidae)
Comparative biochemistry and physiology. Part B Biochemistry & molecular biology, 1995Co-Authors: Diana E. Wheeler, Teresa MartinezAbstract:Storage proteins are a major feature of holometabolous development in insects, accumulating during the larval period and disappearing during metamorphosis. In ants (Hymenoptera:Formicidae), storage proteins also play important roles in adult females. Three types of storage proteins have been characterized from ants: Hexamerins, proteins high in glutamine/glutamic acid, and very high density lipoproteins (VHDLs). The Hexamerins have moderately high levels of aromatic amino acids and belong to the arthropod hemocyanin family of proteins. The proteins high in glutamine/glutamic acid can form hexamers under some conditions, but the subunit size is larger than that of typical Hexamerins. The VHDLs are dimeric and share features with storage chromoproteins described from Lepidoptera. In Camponotus festinatus (Formicinae), storage proteins are found in adult ants in two situations. First, lack of brood stimulates workers to accumulate the same two storage hexamers found in larvae. Second, young virgin queens store large reserves of these proteins before mating. Protein storage by queens has been confirmed in two other subfamilies of ants, indicating it is widespread. The capacity to store proteins as adults enables queens to rear brood without leaving the nest and workers to store rich reserves and regulate larval diet seasonally.
Márcia Maria Gentile Bitondi - One of the best experts on this subject based on the ideXlab platform.
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The HEX 110 Hexamerin Is a Cytoplasmic and Nucleolar Protein in the Ovaries of Apis mellifera.
PloS one, 2016Co-Authors: Juliana Martins, Márcia Maria Gentile BitondiAbstract:Hexamerins are insect storage proteins abundantly secreted by the larval fat body into the haemolymph. The canonical role of Hexamerins consists of serving as an amino acid reserve for development toward the adult stage. However, in Apis mellifera, immunofluorescence assays coupled to confocal laser-scanning microscopy, and high-throughput sequencing, have recently shown the presence of Hexamerins in other organs than the fat body. These findings have led us to study these proteins with the expectation of uncovering additional functions in insect development. We show here that a honeybee hexamerin, HEX 110, localizes in the cytoplasm and nucleus of ovarian cells. In the nucleus of somatic and germline cells, HEX 110 colocalized with a nucleolar protein, fibrillarin, suggesting a structural or even regulatory function in the nucleolus. RNase A provoked the loss of HEX 110 signals in the ovarioles, indicating that the subcellular localization depends on RNA. This was reinforced by incubating ovaries with pyronin Y, a RNA-specific dye. Together, the colocalization with fibrillarin and pyronin Y, and the sensitivity to RNase, highlight unprecedented roles for HEX110 in the nucleolus, the nuclear structure harbouring the gene cluster involved in ribosomal RNA production. However, the similar patterns of HEX 110 foci distribution in the active and inactive ovaries of queens and workers preclude its association with the functional status of these organs.
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Nuclear Immunolocalization of Hexamerins in the Fat Body of Metamorphosing Honey Bees
Insects, 2012Co-Authors: Juliana Martins, Márcia Maria Gentile BitondiAbstract:Hexamerins are storage proteins with primordial functions in insect metamorphosis. They are actively secreted by the larval fat body and stored in the hemolymph. During metamorphosis, they return to the fat body to be processed. For decades, these proteins were thought to exclusively function as an amino acid source for tissue reconstruction during the non-feeding pupal and pharate adult stages and, in some species, for egg production. Recently, new findings have linked the Hexamerins to caste polyphenism and gonad development in social insects. To explore the roles of Hexamerins during the honey bee metamorphosis, we used specific antibodies in expression analysis by western blot, in situ immunolocalization by confocal laser-scanning microscopy and in vivo injections to lower their endogenous levels. Our expression analysis highlighted the changing expression patterns in the fat body and hemolymph during development, which is consistent with the temporal dynamics of hexamerin secretion, storage and depletion. Confocal microscopy showed hexamerin expression in the cytoplasm of both types of fat body cells, trophocytes and oenocytes. Notably, hexamerin foci were also found in the nuclei of these cells, thus confirming our western blot analysis of fat body nuclear-enriched fractions. We also observed that the decrease in soluble Hexamerins in antibody-treated pharate adults led to a precocious adult ecdysis, perhaps in response to the lack (or decrease) in hexamerin-derived amino acids. Taken together, these findings indicate that Hexamerins have other functions in addition to their well-established role as amino acid sources for development.
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A Honey Bee Hexamerin, HEX 70a, Is Likely to Play an Intranuclear Role in Developing and Mature Ovarioles and Testioles
PloS one, 2011Co-Authors: Juliana Martins, Zilá Luz Paulino Simões, Lucas Anhezini, Rodrigo Pires Dallacqua, Márcia Maria Gentile BitondiAbstract:Insect Hexamerins have long been known as storage proteins that are massively synthesized by the larval fat body and secreted into hemolymph. Following the larval-to-pupal molt, Hexamerins are sequestered by the fat body via receptor-mediated endocytosis, broken up, and used as amino acid resources for metamorphosis. In the honey bee, the transcript and protein subunit of a hexamerin, HEX 70a, were also detected in ovaries and testes. Aiming to identify the subcellular localization of HEX 70a in the female and male gonads, we used a specific antibody in whole mount preparations of ovaries and testes for analysis by confocal laser-scanning microscopy. Intranuclear HEX 70a foci were evidenced in germ and somatic cells of ovarioles and testioles of pharate-adult workers and drones, suggesting a regulatory or structural role. Following injection of the thymidine analog EdU we observed co-labeling with HEX 70a in ovariole cell nuclei, inferring possible HEX 70a involvement in cell proliferation. Further support to this hypothesis came from an injection of anti-HEX 70a into newly ecdysed queen pupae where it had a negative effect on ovariole thickening. HEX 70a foci were also detected in ovarioles of egg laying queens, particularly in the nuclei of the highly polyploid nurse cells and in proliferating follicle cells. Additional roles for this storage protein are indicated by the detection of nuclear HEX 70a foci in post-meiotic spermatids and spermatozoa. Taken together, these results imply undescribed roles for HEX 70a in the developing gonads of the honey bee and raise the possibility that other Hexamerins may also have tissue specific functions.
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The four hexamerin genes in the honey bee: structure, molecular evolution and function deduced from expression patterns in queens, workers and drones.
BMC molecular biology, 2010Co-Authors: Juliana Martins, Francis Mf Nunes, Alexandre S. Cristino, Zilá Luz Paulino Simões, Márcia Maria Gentile BitondiAbstract:Background Hexamerins are hemocyanin-derived proteins that have lost the ability to bind copper ions and transport oxygen; instead, they became storage proteins. The current study aimed to broaden our knowledge on the hexamerin genes found in the honey bee genome by exploring their structural characteristics, expression profiles, evolution, and functions in the life cycle of workers, drones and queens.
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A honeybee storage protein gene, hex 70a, expressed in developing gonads and nutritionally regulated in adult fat body
Journal of insect physiology, 2008Co-Authors: Juliana Martins, Francis Mf Nunes, Zilá Luz Paulino Simões, Márcia Maria Gentile BitondiAbstract:In preparing for metamorphosis, insect larvae store a huge amount of proteins in hemolymph, mainly Hexamerins. Out of the four Hexamerins present in the honeybee larvae, one, HEX 70a, exhibited a distinct developmental pattern, especially since it is also present in adults. Here, we report sequence data and experimental evidence suggesting alternative functions for HEX 70a, besides its well-known role as an amino acid resource during metamorphosis. The hex 70a gene consists of 6 exons and encodes a 684 amino acid chain containing the conserved hemocyanin N, M, and C domains. HEX 70a classifies as an arylphorin since it contains more than 15% of aromatic amino acids. In the fat body of adult workers, hex 70a expression turned out to be a nutrient-limited process. However, the fat body is not the only site for hex 70a expression. Both, transcript and protein subunits were also detected in developing gonads from workers, queens and drones, suggesting a role in ovary differentiation and testes maturation and functioning. In its putative reproductive role, HEX 70a however differs from the yolk protein, vitellogenin, since it was not detected in eggs or embryos.
Klaus Scheller - One of the best experts on this subject based on the ideXlab platform.
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Functional dissection of the hexamerin receptor and its ligand arylphorin in the blowfly Calliphora vicina
Insect molecular biology, 2003Co-Authors: Immo A. Hansen, V. Gutsmann, Susanne R. Meyer, Klaus SchellerAbstract:The process of receptor-mediated uptake of hexamerin storage proteins from insect haemolymph by fat body cells is a unique feature of the class Insecta. We identified the binding domains of the hexamerin receptor and the hexamerin ligand arylphorin in the blowfly, by means of the yeast-two-hybrid-system. The receptor-binding domain of arylphorin was located within domain 3 of the arylphorin monomer. The ligand-binding domain of the hexamerin receptor was mapped to the extreme N-terminus of the receptor. The binding domains identified exhibit no similarity to any functional protein domains known to date. Additionally, we identified two previously unknown protein-interactors of the hexamerin receptor. The results of this study provide further insights regarding the mechanism of the receptor-mediated endocytosis of storage proteins in insects.
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Tyrosine kinase mediated phosphorylation of the hexamerin receptor in the rice moth Corcyra cephalonica by ecdysteroids.
Insect biochemistry and molecular biology, 2003Co-Authors: Abul Arif, Klaus Scheller, Aparna Dutta-guptaAbstract:Hexamerins are multifunctional insect storage proteins utilized during metamorphosis of holometabolous insects. These proteins are stage specifically taken up by the fat body cells from the haemolymph due to receptor-mediated endocytosis. The hexamerin receptor and the concomitant hexamerin sequestration in the rice moth Corcyra cephalonica is controlled by the steroid hormone 20-hydroxy-ecdysone (20E). However, the mechanism of receptor activation for hexamerin uptake is not yet clear. We report here that 20E stimulates the phosphorylation of 120 kDa hexamerin binding protein which has been demonstrated to represent the receptor. Phosphorylation of the receptor is suggested to be essential for receptor activation and occurs prior to the hexamerin uptake. The 20E stimulated phosphorylation is mediated partly by a tyrosine kinase as phosphotyrosine antibodies cross-react with the receptor and its phosphorylation is blocked partly by genistein. Back phosphorylation study provides additional evidence for 20E regulation of hexamerin receptor phosphorylation in intact fat body. The receptor phosphorylation is developmentally regulated. This is the first report demonstrating that (i) the uptake of hexamerin is dependent on the phosphorylation of hexamerin receptor and (ii) the phosphorylation is catalyzed partly by a tyrosine kinase which is activated by 20E through a non-genomic action.
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Complete sequence, expression and evolution of two members of the hexamerin protein family during the larval development of the rice moth, Corcyra cephalonica
Insect biochemistry and molecular biology, 2003Co-Authors: P. Nagamanju, Klaus Scheller, Immo A. Hansen, Susanne R. Meyer, Thorsten Burmester, Aparna Dutta-guptaAbstract:Three distinct types of storage Hexamerins are expressed in the "last-instar" larvae of the rice moth, Corcyra cephalonica. A cDNA expression library was constructed from fat body-RNA and screened with a polyclonal antibody raised against purified hexamerin (SP2) of Corcyra cephalonica. Two slightly different "full-length" hexamerin cDNA clones (Hex2a and Hex2b) were isolated and sequenced. Both include open reading frames of 2109 bp which are translated into polypeptides of 703 amino acids with 92.5% identity. Signal peptides of 19 amino acids are present at the N-termini. The 684 amino acids native proteins have a high content of aryl groups (17.6%). According to both the criteria for amino acid composition and the phylogenetic analysis, Hex2a and Hex2b belong to the lepidopteran arylphorins. Northern blot studies revealed that the Hex2 genes are species- and tissue-specifically expressed in fat body cells of "last-instar" (= 5th) larvae.
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Interaction of the anterior fat body protein with the hexamerin receptor in the blowfly Calliphora vicina.
European journal of biochemistry, 2002Co-Authors: Immo A. Hansen, Susanne R. Meyer, Ingo Schäfer, Klaus SchellerAbstract:In late larvae of the blowfly, Calliphora vicina, arylphorin and LSP-2 proteins, which belong to the class of Hexamerins, are selectively taken up by the fat body from the haemolymph. Hexamerin endocytosis is mediated by a specific membrane-bound receptor, the arylphorin-binding protein (ABP). Using the two-hybrid technique, we found that the anterior fat body protein (AFP) interacts with the hexamerin receptor. AFP, a homologue of the mammalian calcium-binding liver protein regucalcin (senescence marker protein-30), exhibits a strong binding affinity for a naturally occurring C-terminal cleavage fragment of the hexamerin receptor precursor (the P30 peptide) and other receptor cleavage products that contain P30. Expression of AFP mRNA and protein is restricted to the anterior part of the fat body tissue and to haemocytes in last-instar larvae. AFP mRNA occurs in all postembryonic developmental stages. Our results suggest that AFP plays a role in the regulation of hexamerin uptake by fat body cells along the anterior-posterior axis.
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Ligands and receptors: common theme in insect storage protein transport.
Die Naturwissenschaften, 1999Co-Authors: Thorsten Burmester, Klaus SchellerAbstract:The passage of macromolecules through biological membranes is an essential process for all multicellular organisms. Insects have developed a mechanism different from that known for all other eukaryotes investigated so far. This review discusses the function and evolution of this mechanism. Insect pupae do not feed during metamorphosis. Therefore they depend on material that has been accumulated during the larval life. At the end of this period, shortly before pupariation, a rise in titer of ecdysteroid hormones induces the incorporation of a large fraction of storage proteins (Hexamerins) from the body fluid into the fat body cells. The transport of Hexamerins across the cell-membrane is mediated by a specific ecdysteroid-controlled receptor. It is synthesized as a precursor protein that is subsequently processed into the active receptor. This receptor protein is very unusual because it is closely related to its own hexamerin ligand. Sequence comparison shows that the Hexamerins and hexamerin receptors diverged early in insect evolution and derive from a common hemocyanin ancestor.
M M G Bitondi - One of the best experts on this subject based on the ideXlab platform.
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Organization, evolution and transcriptional profile of hexamerin genes of the parasitic wasp Nasonia vitripennis (Hymenoptera: Pteromalidae).
Insect molecular biology, 2010Co-Authors: A S Cristino, F M F Nunes, A R Barchuk, V M Aguiar-coelho, Z L P Simões, M M G BitondiAbstract:Hexamerins and prophenoloxidases (PPOs) proteins are members of the arthropod-haemocyanin superfamily. In contrast to haemocyanin and PPO, Hexamerins do not bind oxygen, but mainly play a role as storage proteins that supply amino acids for insect metamorphosis. We identified seven genes encoding Hexamerins, three encoding PPOs, and one hexamerin pseudogene in the genome of the parasitoid wasp Nasonia vitripennis. A phylogenetic analysis of Hexamerins and PPOs from this wasp and related proteins from other insect orders suggests an essentially order-specific radiation of Hexamerins. Temporal and spatial transcriptional profiles of N. vitripennis Hexamerins suggest that they have physiological functions other than metamorphosis, which are arguably coupled with its lifestyle.