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首页> 外文期刊>Molecular and Cellular Biology >Molecular cloning and characterization of a novel type of regulatory protein (GDI) for smg p25A, a ras p21-like GTP-binding protein.
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Molecular cloning and characterization of a novel type of regulatory protein (GDI) for smg p25A, a ras p21-like GTP-binding protein.

机译：用于smg p25A（一种ras p21样GTP结合蛋白）的新型调控蛋白（GDI）的分子克隆和表征。

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We recently purified to near homogeneity a novel type of regulatory protein for smg p25A, a ras p21-like GTP-binding protein, from bovine brain cytosol. This regulatory protein, named smg p25A GDP dissociation inhibitor (GDI), regulates the GDP-GTP exchange reaction of smg p25A by inhibiting dissociation of GDP from and subsequent binding of GTP to it. In the present studies, we isolated and sequenced the cDNA of smg p25A GDI from a bovine brain cDNA library by using an oligonucleotide probe designed from the partial amino acid sequence of purified smg p25A GDI. The cDNA has an open reading frame that encodes a protein of 447 amino acids with a calculated Mr of 50,565. This Mr is similar to those of the purified smg p25A GDI estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and sucrose density gradient ultracentrifugation, which are about 54,000 and 65,000, respectively. The isolated cDNA is expressed in Escherichia coli, and the encoded protein exhibits GDI activity. smg p25A GDI is hydrophilic overall, except for one hydrophobic region near the N terminus. smg p25A GDI shares low amino acid sequence homology with the Saccharomyces cerevisiae CDC25-encoded protein, which has been suggested to serve as a factor that regulates the GDP-GTP exchange reaction of the yeast RAS2-encoded protein, but not with the beta gamma subunits of GTP-binding proteins having an alpha beta gamma subunit structure, such as Gs and Gi. The smg p25A GDI mRNA was present in various tissues, including not only tissues in which smg p25A was detectable but also tissues in which it was not detectable. This fact has raised the possibility that smg p25A GDI interacts with another G protein in tissues in which smg p25A is absent.
机译：我们最近从牛脑细胞溶质中纯化了一种新型的smg p25A调控蛋白，一种ras p21样GTP结合蛋白。这种调节蛋白称为smg p25A GDP解离抑制剂（GDI），它通过抑制GDP与GTP的分离以及随后与GTP的结合来调节smg p25A的GDP-GTP交换反应。在本研究中，我们使用从纯化的smg p25A GDI的部分氨基酸序列设计的寡核苷酸探针，从牛脑cDNA文库中分离并测序了smg p25A GDI的cDNA。 cDNA具有可读框，可编码447个氨基酸的蛋白质，Mr为50,565。该Mr类似于通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳和蔗糖密度梯度超速离心法估计的纯化smg p25A GDI的Mr，分别为约54,000和65,000。分离的cDNA在大肠杆菌中表达，并且编码的蛋白质表现出GDI活性。 smg p25A GDI总体上是亲水的，除了靠近N端的一个疏水区域。 smg p25A GDI与酿酒酵母CDC25编码的蛋白质具有低氨基酸序列同源性，已提出该蛋白质可作为调节酵母RAS2编码的蛋白质的GDP-GTP交换反应的因子，但与βγ亚基无关具有αβγ亚基结构的GTP结合蛋白，例如Gs和Gi。 smg p25A GDI mRNA存在于各种组织中，不仅包括可检测到smg p25A的组织，还包括不可检测到的组织。这一事实增加了在没有smg p25A的组织中smg p25A GDI与另一种G蛋白相互作用的可能性。

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