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首页> 外文期刊>Journal of bacteriology >Escherichia coli DNA Polymerase III τ- and γ-Subunit Conserved Residues Required for Activity In Vivo and In Vitro
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Escherichia coli DNA Polymerase III τ- and γ-Subunit Conserved Residues Required for Activity In Vivo and In Vitro

机译：体内和体外活性所需的大肠杆菌DNA聚合酶III的τ和γ亚基保守残基

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摘要

The Escherichia coli DNA polymerase III τ and γ subunits are single-strand DNA-dependent ATPases (the latter requires the δ and δ′ subunits for significant ATPase activity) involved in loading processivity clamp β. They are homologous to clamp-loading proteins of many organisms from phages to humans. Alignment of 27 prokaryotic τ/γ homologs and 1 eukaryotic τ/γ homolog has refined the sequences of nine previously defined identity and functional motifs. Mutational analysis has defined highly conserved residues required for activity in vivo and in vitro. Specifically, mutations introduced into highly conserved residues within three of those motifs, the P loop, the DExx region, and the SRC region, inactivated complementing activity in vivo and clamp loading in vitro and reduced ATPase catalytic efficiency in vitro. Mutation of a highly conserved residue within a fourth motif, VIc, inactivated clamp-loading activity and reduced ATPase activity in vitro, but the mutant gene, on a multicopy plasmid, retained complementing activity in vivo and the mutant gene also supported apparently normal replication and growth as a haploid, chromosomal allele.
机译：大肠埃希氏菌DNA聚合酶IIIτ和γ亚基是单链DNA依赖的ATPase（后者需要δ和δ'亚基才能显着增强ATPase的活性），参与了负载过程钳位β的作用。它们与将多种生物的蛋白质从噬菌体夹入人类的同源。 27个原核τ/γ同源物和1个真核τ/γ同源物的比对完善了9个先前定义的同一性和功能基序的序列。突变分析已定义了体内和体外活性所需的高度保守的残基。具体而言，将突变引入其中三个基序（P环，DExx区和SRC区）内高度保守的残基中，会使体内的补体活性失活，并在体外钳夹负载，并降低体外的ATPase催化效率。在体外，第四个基序VIc中高度保守的残基发生突变，失活了钳位活性并降低了ATPase活性，但在多拷贝质粒上的突变基因在体内保留了互补活性，并且该突变基因还明显支持正常复制和生长为单倍体，染色体等位基因。

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