Pandit Shashi B, Srinivasan N
Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India.
Proteins. 2003 Sep 1;52(4):585-97. doi: 10.1002/prot.10420.
The members of the family of G-proteins are characterized by their ability to bind and hydrolyze guanosine triphosphate (GTP) to guanosine diphosphate (GDP). Despite a common biochemical function of GTP hydrolysis shared among the members of the family of G-proteins, they are associated with diverse biological roles. The current work describes the identification and detailed analysis of the putative G-proteins encoded in the completely sequenced prokaryotic genomes. Inferences on the biological roles of these G-proteins have been obtained by their classification into known functional subfamilies. We have identified 497 G-proteins in 42 genomes. Seven small GTP-binding protein homologues have been identified in prokaryotes with at least two of the diagnostic sequence motifs of G-proteins conserved. The translation factors have the largest representation (234 sequences) and are found to be ubiquitous, which is consistent with their critical role in protein synthesis. The GTP_OBG subfamily comprises of 79 sequences in our dataset. A total of 177 sequences belong to the subfamily of GTPase of unknown function and 154 of these could be associated with domains of known functions such as cell cycle regulation and t-RNA modification. The large GTP-binding proteins and the alpha-subunit of heterotrimeric G-proteins are not detected in the genomes of the prokaryotes surveyed.
G蛋白家族成员的特点是能够结合并将三磷酸鸟苷（GTP）水解为二磷酸鸟苷（GDP）。尽管G蛋白家族成员具有共同的GTP水解生化功能，但它们与多种生物学作用相关。当前的工作描述了在完全测序的原核生物基因组中编码的假定G蛋白的鉴定和详细分析。通过将这些G蛋白分类到已知的功能亚家族中，得出了关于它们生物学作用的推论。我们在42个基因组中鉴定出497个G蛋白。在原核生物中鉴定出7个小GTP结合蛋白同源物，其中至少有两个G蛋白的诊断序列基序是保守的。翻译因子的数量最多（234个序列），并且发现它们无处不在，这与其在蛋白质合成中的关键作用一致。在我们的数据集中，GTP_OBG亚家族包含79个序列。共有177个序列属于功能未知的GTP酶亚家族，其中154个可能与已知功能的结构域相关，如细胞周期调控和tRNA修饰。在所调查的原核生物基因组中未检测到大GTP结合蛋白和异源三聚体G蛋白的α亚基。
