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Yoshinori Nozawa - One of the best experts on this subject based on the ideXlab platform.
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possible interaction of haemoglobin with a low mr GTP Binding Protein ram p25
Iubmb Life, 1995Co-Authors: Koh-ichi Nagata, Yukio Okano, Yoshinori NozawaAbstract:: Haemoblobin (Hb) was observed to inhibit the GDP/GTP exchange activity of a low M(r) GTP-Binding Protein, ram p25. Hb also inhibited the [32P]GTP-hydrolysis activity of ram p25. These inhibitory effects of Hb were lost after incubation of Hb at 80 degrees C for 3 min, indicating that the ternary tetrameric structure of Hb is essential for the inhibitory effects on ram p25 activities. Hb did not inhibit [35S]GTP gamma S-Binding of nucleotide-free ram p25. Methaemoglobin (MetHb) also inhibited both [3H]GDP-dissociation and [32P]GTP-hydrolysis activities of ram p25 in a very similar manner to Hb. The results strongly suggest that Hb may suppress physiological function(s) of ram p25 in vivo by inhibiting both [32P]GTP-hydrolysis and [3H]GDP-dissociation of ram p25.
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Localization of a low Mr GTP-Binding Protein, rap1 Protein, in plasma membranes and secretory granule membranes of rat parotid gland.
Life sciences, 1994Co-Authors: Yasunaga Kameyama, Koh-ichi Nagata, Masako Mizuno-kamiya, Yutaka Yokota, Atsushi Fujita, Yoshinori NozawaAbstract:Abstract Subcellular fractions were prepared from rat parotid gland by sequential centrifugation, Percoll gradient centrifugation and divalent-cation precipitation, and the localization of a low Mr GTP-Binding Protein, rap1 Protein (rap1p) was analyzed by immunoblotting using a specific antibody. rap1p was found to be located in apical and basolateral plasma membranes, and secretory granule membranes in rat parotid gland. On the other hand, the βγ subunits of heterotrimeric Gt Protein was localized in plasma membranes but not in granule membranes.
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evidence for the presence of a low mr GTP Binding Protein ram p25 in human platelet membranes
Platelets, 1993Co-Authors: Koh-ichi Nagata, Yukio Okano, T Suzuki, Yoshinori NozawaAbstract:The ram gene was isolated from a rat megakaryocyte cDNA library and encodes a GTP-Binding Protein with a Mr of 25 000. In order to clarify the presence of the ram Protein (ram p25) in human platelets, we tried to purify ram p25 from the sodium cholate extract of human platelet membranes by a combination of DEAE-Sephacel, Sephacryl S300HR, hydroxyapatite HCA-100S and DEAE-Toyopearl 650(S) column chromatographies. In the course of the purification, a specific antibody raised against a synthetic COOH-terminal peptide of ram p25 was used. In conclusion, ram p25 was partially purified and was observed to be present in membrane fractions of human platelets.
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characterization of a gly19 val mutant of ram p25 a low mr GTP Binding Protein loss of GTP gdp Binding activity in the mutated ram p25
Biochemical and Biophysical Research Communications, 1992Co-Authors: Koh-ichi Nagata, Yukio Okano, T Suzuki, Michinari Hamaguchi, Yoshinori NozawaAbstract:Abstract A substitution of Gly for Val at position 19, which corresponds to oncogenic Gly13→ Val mutation of ras p21, was introduced in a low Mr GTP-Binding Protein, ram p25. The Protein was expressed in cytosolic fraction of Escherichia coli and purified by using specific antibody raised against ram p25. The mutated Protein had no guanine nucleotide-Binding activity although [Val13]ras p21 was reported to have. The analysis of guanine nucleotide composition of the purified [Va119]ram p25 revealed that the Protein was free of nucleotide whereas the normal ram p25 bound about 1 mol of GDP per mol of Protein. These results strongly suggested that some part(s) of variable regions as well as the consensus regions are important for the biochemical properties of ram p25.
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characterization and site directed mutagenesis of a low m r GTP Binding Protein ram p25 expressed in escherichia coli
Journal of Biological Chemistry, 1992Co-Authors: Koh-ichi Nagata, Yukio Okano, T Suzuki, Y Shibagaki, Kiyohisa Mizumoto, Yoshito Kaziro, Yoshinori NozawaAbstract:Abstract The ram gene encodes a GTP-Binding Protein with a M(r) of 25,068 (Nagata, K., Satoh, T., Itoh, H., Kozasa, T., Okano, Y., Doi, T., Kaziro, Y., and Nozawa, Y. (1990) FEBS Lett. 275, 29-32). It has a putative effector domain very similar to that of yeast SEC4 Protein, and shares 40% identity and 60% homology with it, respectively. In order to analyze the biochemical properties, ram cDNA was engineered and inserted into a bacterial expression vector; this allowed the production at a high level of soluble recombinant ram p25 in Escherichia coli. The purified ram p25 contained an equimolar amount of GDP. The purified Protein bound approximately 1 mol of [35S]guanosine 5'-O-(thiotriphosphate) GTP gamma S)/mol of Protein, with a Kd value of 120 nM. [35S]GTP gamma S Binding to this Protein was inhibited by GTP and GDP, but not by ATP and ADP. In the presence of 10 mM Mg2+, the dissociation of [8,5'-3H]GDP and [35S]GTP gamma S from ram p25 occurred with rates of 0.015 min-1 and 0.004 min-1, respectively, showing that the ram p25 has a higher affinity for GTP than GDP. The rate of release of Pi from [gamma-32P]GTP-bound ram p25 was calculated to be 0.011 min-1. The contribution of guanine nucleotide-Binding and GTP-hydrolysis domains of the Protein to its biochemical activities was investigated by site-directed mutagenesis. Substitution of Val for Gly at position 19 resulted in disappearance of [35S]GTP gamma S- and [3H]GDP-Binding activity in spite of good expression of the Protein. Mutations of Thr41 to Ser, Ala76 to Thr, and Asn133 to His slightly increased the rates of [35S] GTP gamma S Binding and [3H]GDP dissociation, but had almost no effects on the manner of [gamma-32P]GTP hydrolysis. Replacement of Gln78 with Leu significantly increased the [3H]GDP dissociation rate (7-fold) and decreased GTP hydrolytic activity considerably.
Koh-ichi Nagata - One of the best experts on this subject based on the ideXlab platform.
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identification and localization of gene expression of a low mr GTP Binding Protein ram p25 in pituitary gland
Biochemical and Biophysical Research Communications, 1995Co-Authors: Koh-ichi Nagata, H Sakagami, Hisatake Kondo, Y NozawaAbstract:Abstract The localization of gene expression of a low Mr GTP-Binding Protein, ram p25, was examined throughout the entire brain of adult rat by in situ hybridization. ram -mRNA was expressed predominantly in anterior and intermediate lobes of pituitary gland (hypophysis), and weakly in hippocampal formation. In other parts of brain, no significant expression of ram -mRNA was detected, indicating that ram p25 may have an important role(s) in adenohypophysis. In 15-day fetal rat, the mRNA was observed to be expressed strongly in the primitive anterior lobe of pituitary gland. The ram p25 was also detected in bovine pituitary gland by a specific antibody and was purified to near homogeneity by stepwise column chromatographies. Biochemical characterization of the purified ram p25 revealed that the profile of [ 35 S]GTP γ S-Binding activity was almost the same as that of recombinant ram p25 expressed in E. coli .
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possible interaction of haemoglobin with a low mr GTP Binding Protein ram p25
Iubmb Life, 1995Co-Authors: Koh-ichi Nagata, Yukio Okano, Yoshinori NozawaAbstract:: Haemoblobin (Hb) was observed to inhibit the GDP/GTP exchange activity of a low M(r) GTP-Binding Protein, ram p25. Hb also inhibited the [32P]GTP-hydrolysis activity of ram p25. These inhibitory effects of Hb were lost after incubation of Hb at 80 degrees C for 3 min, indicating that the ternary tetrameric structure of Hb is essential for the inhibitory effects on ram p25 activities. Hb did not inhibit [35S]GTP gamma S-Binding of nucleotide-free ram p25. Methaemoglobin (MetHb) also inhibited both [3H]GDP-dissociation and [32P]GTP-hydrolysis activities of ram p25 in a very similar manner to Hb. The results strongly suggest that Hb may suppress physiological function(s) of ram p25 in vivo by inhibiting both [32P]GTP-hydrolysis and [3H]GDP-dissociation of ram p25.
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Localization of a low Mr GTP-Binding Protein, rap1 Protein, in plasma membranes and secretory granule membranes of rat parotid gland.
Life sciences, 1994Co-Authors: Yasunaga Kameyama, Koh-ichi Nagata, Masako Mizuno-kamiya, Yutaka Yokota, Atsushi Fujita, Yoshinori NozawaAbstract:Abstract Subcellular fractions were prepared from rat parotid gland by sequential centrifugation, Percoll gradient centrifugation and divalent-cation precipitation, and the localization of a low Mr GTP-Binding Protein, rap1 Protein (rap1p) was analyzed by immunoblotting using a specific antibody. rap1p was found to be located in apical and basolateral plasma membranes, and secretory granule membranes in rat parotid gland. On the other hand, the βγ subunits of heterotrimeric Gt Protein was localized in plasma membranes but not in granule membranes.
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evidence for the presence of a low mr GTP Binding Protein ram p25 in human platelet membranes
Platelets, 1993Co-Authors: Koh-ichi Nagata, Yukio Okano, T Suzuki, Yoshinori NozawaAbstract:The ram gene was isolated from a rat megakaryocyte cDNA library and encodes a GTP-Binding Protein with a Mr of 25 000. In order to clarify the presence of the ram Protein (ram p25) in human platelets, we tried to purify ram p25 from the sodium cholate extract of human platelet membranes by a combination of DEAE-Sephacel, Sephacryl S300HR, hydroxyapatite HCA-100S and DEAE-Toyopearl 650(S) column chromatographies. In the course of the purification, a specific antibody raised against a synthetic COOH-terminal peptide of ram p25 was used. In conclusion, ram p25 was partially purified and was observed to be present in membrane fractions of human platelets.
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characterization of a gly19 val mutant of ram p25 a low mr GTP Binding Protein loss of GTP gdp Binding activity in the mutated ram p25
Biochemical and Biophysical Research Communications, 1992Co-Authors: Koh-ichi Nagata, Yukio Okano, T Suzuki, Michinari Hamaguchi, Yoshinori NozawaAbstract:Abstract A substitution of Gly for Val at position 19, which corresponds to oncogenic Gly13→ Val mutation of ras p21, was introduced in a low Mr GTP-Binding Protein, ram p25. The Protein was expressed in cytosolic fraction of Escherichia coli and purified by using specific antibody raised against ram p25. The mutated Protein had no guanine nucleotide-Binding activity although [Val13]ras p21 was reported to have. The analysis of guanine nucleotide composition of the purified [Va119]ram p25 revealed that the Protein was free of nucleotide whereas the normal ram p25 bound about 1 mol of GDP per mol of Protein. These results strongly suggested that some part(s) of variable regions as well as the consensus regions are important for the biochemical properties of ram p25.
Atsushi Yoshimura - One of the best experts on this subject based on the ideXlab platform.
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rice gibberellin insensitive dwarf mutant gene dwarf 1 encodes the alpha subunit of GTP Binding Protein
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: Motoyuki Ashikari, Masahiro Yano, Takuji Sasaki, Atsushi YoshimuraAbstract:A rice Dwarf 1 gene was identified by using a map-based cloning strategy. Its recessive mutant allele confers a dwarf phenotype. Linkage analysis revealed that a cDNA encoding the α-subunit of GTP-Binding Protein cosegregated with d1 in 3,185 d1 segregants. Southern hybridization analysis with this cDNA as a probe showed different band patterns in several d1 mutant lines. In at least four independent d1 mutants, no gene transcript was observed by Northern hybridization analysis. Sequencing analysis revealed that an 833-bp deletion had occurred in one of the mutant alleles, which resulted in an inability to express GTP-Binding Protein. A transgenic d1 mutant with GTP-Binding Protein gene restored the normal phenotype. We conclude that the rice Dwarf 1 gene encodes GTP-Binding Protein and that the Protein plays an important role in plant growth and development. Because the d1 mutant is classified as gibberellin-insensitive, we suggest that the GTP-Binding Protein might be associated with gibberellin signal transduction.
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rice gibberellin insensitive dwarf mutant gene dwarf 1 encodes the α subunit of GTP Binding Protein
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: Motoyuki Ashikari, Masahiro Yano, Takuji Sasaki, Atsushi YoshimuraAbstract:A rice Dwarf 1 gene was identified by using a map-based cloning strategy. Its recessive mutant allele confers a dwarf phenotype. Linkage analysis revealed that a cDNA encoding the α-subunit of GTP-Binding Protein cosegregated with d1 in 3,185 d1 segregants. Southern hybridization analysis with this cDNA as a probe showed different band patterns in several d1 mutant lines. In at least four independent d1 mutants, no gene transcript was observed by Northern hybridization analysis. Sequencing analysis revealed that an 833-bp deletion had occurred in one of the mutant alleles, which resulted in an inability to express GTP-Binding Protein. A transgenic d1 mutant with GTP-Binding Protein gene restored the normal phenotype. We conclude that the rice Dwarf 1 gene encodes GTP-Binding Protein and that the Protein plays an important role in plant growth and development. Because the d1 mutant is classified as gibberellin-insensitive, we suggest that the GTP-Binding Protein might be associated with gibberellin signal transduction.
Yoshimi Takai - One of the best experts on this subject based on the ideXlab platform.
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statins exert the pleiotropic effects through small GTP Binding Protein dissociation stimulator upregulation with a resultant rac1 degradation
Arteriosclerosis Thrombosis and Vascular Biology, 2013Co-Authors: Shinichi Tanaka, Yoshimi Takai, Yoshihiro Fukumoto, Kotaro Nochioka, Tatsuro Minami, Shun Kudo, Nobuyuki Shiba, Carol L Williams, James K Liao, Hiroaki ShimokawaAbstract:Objective— The pleiotropic effects of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (statins) independent of cholesterol-lowering effects are thought to be mediated through inhibition of the Rho/Rho-kinase pathway. However, we have previously demonstrated that the pleiotropic effects of regular-dose statins are mediated mainly through inhibition of the Rac1 signaling pathway rather than the Rho/Rho-kinase pathway, although the molecular mechanisms of the selective inhibition of the Rac1 signaling pathway by regular-dose statins remain to be elucidated. In this study, we tested our hypothesis that small GTP-Binding Protein GDP dissociation stimulator (SmgGDS) plays a crucial role in the molecular mechanisms of the Rac1 signaling pathway inhibition by statins in endothelial cells. Approach and Results— In cultured human umbilical venous endothelial cells, statins concentration-dependently increased SmgGDS expression and decreased nuclear Rac1. Statins also enhanced SmgGDS expression in mouse aorta. In control mice, the protective effects of statins against angiotensin II–induced medial thickening of coronary arteries and fibrosis were noted, whereas in SmgGDS-deficient mice, the protective effects of statins were absent. When SmgGDS was knocked down by its small interfering RNA in human umbilical venous endothelial cells, statins were no longer able to induce Rac1 degradation or inhibit angiotensin II–induced production of reactive oxygen species. Finally, in normal healthy volunteers, statins significantly increased SmgGDS expression with a significant negative correlation between SmgGDS expression and oxidative stress markers, whereas no correlation was noted with total or low-density lipoProtein-cholesterol. Conclusions— These results indicate that statins exert their pleiotropic effects through SmgGDS upregulation with a resultant Rac1 degradation and reduced oxidative stress in animals and humans.
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activation of brain b raf Protein kinase by rap1b small GTP Binding Protein
Journal of Biological Chemistry, 1996Co-Authors: Toshihisa Ohtsuka, Kazuya Shimizu, Bunpei Yamamori, Shinya Kuroda, Yoshimi TakaiAbstract:Rap1 small GTP-Binding Protein has the same amino acid sequence at its effector domain as that of Ras. Rap1 has been shown to antagonize the Ras functions, such as the Ras-induced transformation of NIH 3T3 cells and the Ras-induced activation of the c-Raf-1 Protein kinase-dependent mitogen-activated Protein (MAP) kinase cascade in Rat-1 cells, whereas we have shown that Rap1 as well as Ras stimulates DNA synthesis in Swiss 3T3 cells. We have established a cell-free assay system in which Ras activates bovine brain B-Raf Protein kinase. Here we have used this assay system and examined the effect of Rap1 on the B-Raf activity to phosphorylate recombinant MAP kinase kinase (MEK). Recombinant Rap1B stimulated the activity of B-Raf, which was partially purified from bovine brain and immunoprecipitated by an anti-B-Raf antibody. The GTP-bound form was active, but the GDP-bound form was inactive. The fully post-translationally lipid-modified form was active, but the unmodified form was nearly inactive. The maximum B-Raf activity stimulated by Rap1B was nearly the same as that stimulated by Ki-Ras. Rap1B enhanced the Ki-Ras-stimulated B-Raf activity in an additive manner. These results indicate that not only Ras but also Rap1 is involved in the activation of the B-Raf-dependent MAP kinase cascade.
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possible involvement of rab11 p24 a ras like small GTP Binding Protein in intracellular vesicular transport of isolated pancreatic acini
Digestive Diseases and Sciences, 1996Co-Authors: Yuichi Hori, Kozo Kaibuchi, Yoshifumi Takeyama, Motoki Hiroyoshi, Takashi Ueda, Akio Maeda, Harumasa Ohyanagi, Yoichi Saitoh, Yoshimi TakaiAbstract:Rab11 p24 is a Ras-like small guanosine triphosphate (GTP)-Binding Protein, and specific antibodies against it were newly developed to explore its function. Using the antibody, Rab11 p24 was shown to be abundant in rat pancreas as well as in most rat tissues. To explore the involvement of Rab11 p24 into the exocytotic process, the subcellular distribution of Rab11 p24 in rat pancreatic acini was evaluated also by use of the antibody. When the isolated acini were incubated with 1×10−10 M cholecystokinin octapeptide (CCK-8) that induced the maximal stimulation, the amount of Rab11 p24 increased in the fractions of plasma membrane and zymogen granules, but decreased in the cytosol fraction. This redistribution was time-dependent and occurred within 1 min after the CCK-8 stimulation and reached a maximal level within 2 min after the stimulation. Moreover, a light microscopic immunolabeling technique on the isolated rat pancreatic acini also revealed that higher immunoreactivity with Rab11 p24 was observed over the zymogen granule membrane under CCK-8 stimulation. The present results indicate that Rab11 p24 is translocated from cytosol to the membrane fraction during stimulation with CCK-8 and suggest that Rab11 p24 is involved in the intracellular vesicular transport of isolated pancreatic acini.
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a downstream target of rho1 small GTP Binding Protein is pkc1 a homolog of Protein kinase c which leads to activation of the map kinase cascade in saccharomyces cerevisiae
The EMBO Journal, 1995Co-Authors: H Nonaka, Koichi Tanaka, H Hirano, Takeshi Fujiwara, H Kohno, Masato Umikawa, Akihisa Mino, Yoshimi TakaiAbstract:The RHO1 gene in Saccharomyces cerevisiae encodes a homolog of the mammalian RhoA small GTP-Binding Protein, which is implicated in various actin cytoskeleton-dependent cell functions. In yeast, Rho1p is involved in bud formation. A yeast strain in which RHO1 is replaced with RhoA shows a recessive temperature-sensitive growth phenotype. A dominant suppressor mutant was isolated from this strain. Molecular cloning of the suppressor gene revealed that the mutation occurred at the pseuodosubstrate site of PKC1, a yeast homolog of mammalian Protein kinase C. Two-hybrid analysis demonstrated that GTP-Rho1p, but not GDP-Rho1p, interacted with the region of Pkc1p containing the pseudosubstrate site and the C1 domain. MKK1 and MPK1 encode MAP kinase kinase and MAP kinase homologs, respectively, and function downstream of PKC1. A dominant active MKK1-6 mutation or overexpression of MPK1 suppressed the temperature sensitivity of the RhoA mutant. The dominant activating mutation of PKC1 suppressed the temperature sensitivity of the RhoA mutant. The dominant activating mutation of PKC1 suppressed the temperature sensitivity of two effector mutants of RHO1, rho1(F44Y) and rho1(E451), but not that of rho1(V43T). These results indicate that there are at least two signaling pathways regulated by Rho1p and that one of the downstream targets is Pkc1p, leading to the activation of the MAP kinase cascade.
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growth site localization of rho1 small GTP Binding Protein and its involvement in bud formation in saccharomyces cerevisiae
Journal of Cell Biology, 1994Co-Authors: Wataru Yamochi, H Nonaka, Koichi Tanaka, A Maeda, T Musha, Yoshimi TakaiAbstract:The Rho small GTP-Binding Protein family regulates various actomyosin-dependent cell functions, such as cell morphology, locomotion, cytokinesis, membrane ruffling, and smooth muscle contraction. In the yeast Saccharomyces cerevisiae, there is a homologue of mammalian RhoA, RHO1, which is essential for vegetative growth of yeast cells. To explore the function of the RHO1 gene, we isolated a recessive temperature-sensitive mutation of RHO1, rho1-104. The rho1-104 mutation caused amino acid substitutions of Asp 72 to Asn and Cys 164 to Tyr of Rho1p. Strains bearing the rho1-104 mutation accumulated tiny- or small-budded cells in which cortical actin patches were clustered to buds at the restrictive temperature. Cell lysis and cell death were also seen with the rho1-104 mutant. Indirect immunofluorescence microscopic study demonstrated that Rho1p was concentrated to the periphery of the cells where cortical actin patches were clustered, including the site of bud emergence, the tip of the growing buds, and the mother-bud neck region of cells prior to cytokinesis. Indirect immunofluorescence study with cells overexpressing RHO1 suggested that the Rho1p-Binding site was saturable. A mutant Rho1p with an amino acid substitution at the lipid modification site remained in the cytoplasm. These results suggest that Rho1 small GTP-Binding Protein binds to a specific site at the growth region of cells, where Rho1p exerts its function in controlling cell growth.
Motoyuki Ashikari - One of the best experts on this subject based on the ideXlab platform.
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rice gibberellin insensitive dwarf mutant gene dwarf 1 encodes the alpha subunit of GTP Binding Protein
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: Motoyuki Ashikari, Masahiro Yano, Takuji Sasaki, Atsushi YoshimuraAbstract:A rice Dwarf 1 gene was identified by using a map-based cloning strategy. Its recessive mutant allele confers a dwarf phenotype. Linkage analysis revealed that a cDNA encoding the α-subunit of GTP-Binding Protein cosegregated with d1 in 3,185 d1 segregants. Southern hybridization analysis with this cDNA as a probe showed different band patterns in several d1 mutant lines. In at least four independent d1 mutants, no gene transcript was observed by Northern hybridization analysis. Sequencing analysis revealed that an 833-bp deletion had occurred in one of the mutant alleles, which resulted in an inability to express GTP-Binding Protein. A transgenic d1 mutant with GTP-Binding Protein gene restored the normal phenotype. We conclude that the rice Dwarf 1 gene encodes GTP-Binding Protein and that the Protein plays an important role in plant growth and development. Because the d1 mutant is classified as gibberellin-insensitive, we suggest that the GTP-Binding Protein might be associated with gibberellin signal transduction.
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rice gibberellin insensitive dwarf mutant gene dwarf 1 encodes the α subunit of GTP Binding Protein
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: Motoyuki Ashikari, Masahiro Yano, Takuji Sasaki, Atsushi YoshimuraAbstract:A rice Dwarf 1 gene was identified by using a map-based cloning strategy. Its recessive mutant allele confers a dwarf phenotype. Linkage analysis revealed that a cDNA encoding the α-subunit of GTP-Binding Protein cosegregated with d1 in 3,185 d1 segregants. Southern hybridization analysis with this cDNA as a probe showed different band patterns in several d1 mutant lines. In at least four independent d1 mutants, no gene transcript was observed by Northern hybridization analysis. Sequencing analysis revealed that an 833-bp deletion had occurred in one of the mutant alleles, which resulted in an inability to express GTP-Binding Protein. A transgenic d1 mutant with GTP-Binding Protein gene restored the normal phenotype. We conclude that the rice Dwarf 1 gene encodes GTP-Binding Protein and that the Protein plays an important role in plant growth and development. Because the d1 mutant is classified as gibberellin-insensitive, we suggest that the GTP-Binding Protein might be associated with gibberellin signal transduction.
