Sowa M P, Coulter L J, Tait A, Hide G
Wellcome Unit of Molecular Parasitology, University of Glasgow, Glasgow, UK.
Gene. 1999 Apr 16;230(2):155-61. doi: 10.1016/s0378-1119(99)00072-4.
The ras superfamily of GTP binding proteins encompasses a wide range of family members, related by conserved amino-acid motifs, and act as molecular binary switches that play key roles in cellular processes. Gene duplication and divergence has been postulated as the mechanism by which such family members have evolved their specific functions. We have cloned and sequenced a ras-like gene, tbrlp, from the primitive eukaryote Trypanosoma brucei. The gene encodes a protein of 227 amino acids and contains the six conserved subdomains that designate it as a ras/rap subfamily member. However, the presence of key diagnostic residues characteristic of both the ras and rap families of GTP confuse the familial classification of this gene. Phylogenetic analysis of the GTP binding domain places its origins at the divergence point of the ras/rap families and suggests that tbrlp is an ancestral gene to the ras/rap genes of higher eukaryotes.
GTP结合蛋白的ras超家族包含众多家族成员，它们通过保守的氨基酸基序相互关联，并作为分子双开关在细胞过程中发挥关键作用。基因复制和分化被认为是这些家族成员进化出其特定功能的机制。我们从原始真核生物布氏锥虫中克隆并测序了一个类ras基因tbrlp。该基因编码一个227个氨基酸的蛋白质，并包含六个保守亚结构域，这表明它是ras/rap亚家族成员。然而，ras和rap家族GTP特有的关键诊断性残基的存在使该基因的家族分类变得模糊。对GTP结合域的系统发育分析表明，它起源于ras/rap家族的分化点，提示tbrlp是高等真核生物ras/rap基因的祖先基因。
