Evolution of dnaQ, the gene encoding the editing 3' to 5' exonuclease subunit of DNA polymerase III holoenzyme in Gram-negative bacteria
Evolution of dnaQ, the gene encoding the editing 3' to 5' exonuclease subunit of DNA polymerase III holoenzyme in Gram-negative bacteria
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DOI：
10.1016/s0014-5793(96)01361-0
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发表时间：
1997-01-02
期刊：
影响因子：
3.5
通讯作者：
Ito, J
中科院分区：
文献类型：
--
作者：
Huang, YP;Braithwaite, DK;Ito, J
已确定了来自鼠伤寒沙门氏菌和Buchnera aphidicola的编码DNA聚合酶III全酶的ε亚基的dnaQ的核苷酸序列。鼠伤寒沙门氏菌dnaQ蛋白由243个氨基酸残基组成，计算分子量为27 224。Buchnera aphidicola dnaQ蛋白含有233个氨基酸残基，计算分子量为27 170。的dnaQ蛋白质的氨基酸序列和那些从革兰氏阳性细菌的DNA聚合酶MS的多序列比对产生六个同源片段。这些同源片段含有参与催化重要的金属离子结合的高度保守的氨基酸序列基序（配体1、2和3）。然而，发现金属配体4在革兰氏阴性菌中的C家族DNA聚合酶和dnaQ蛋白的3 '-5'外切核酸酶结构域中被改变。根据这些结果，我们提出革兰氏阴性菌的dnaQ基因和革兰氏阳性菌的DNA聚合酶III基因（pol C基因）的最后共同祖先是一个包含3 '-5'外切核酸酶和DNA聚合酶结构域的单一基因，然后革兰氏阴性菌的dnaQ基因与聚合酶基因分离。
The nucleotide sequences of the dnaQ gents from Salmonella typhimurium and Buchnera aphidicola, encoding the epsilon-subunit of the DNA polymerase III holoenzyme, have been determined. The Salmonella typhimurium dnaQ protein consists of 243 amino acid residues with a calculated molecular weight of 27 224. The Buchnera aphidicola dnaQ protein contains 233 amino acid residues with a calculated molecular weight of 27 170. A multiple sequence alignment of the amino acid sequences of the dnaQ proteins and those of DNA polymerase ms from Gram-positive bacteria produced six homologous segments. These homologous segments contain highly conserved amino acid sequence motifs involved in catalytically important metal ion bindings (ligands 1, 2 and 3), Ho,wever, metal ligand 4 is found to be altered in the 3'-5' exonuclease domain of the family C DNA polymerases and dnaQ proteins in Gram-negative bacteria. From these results, we propose that the last common ancestor of the dnaQ gene of Gram-negative bacteria and the DNA polymerase III gene (pol C gene) of Gram-positive bacteria was a single gene containing both 3'-5' exonuclease and DNA polymerase domains and then the dnaQ gene separated from the polymerase gene in Gram-negative bacteria.