Structure and function of dnaQ and mutD mutators of Escherichia coli |
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Authors: | Kyoko Takano Yusaku Nakabeppu Hisaji Maki Takashi Horiuchi and Mutsuo Sekiguchi |
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Institution: | (1) Department of Biology, Faculty of Science and Department of Biochemistry, Faculty of Medicine, Kyushu University, 812 Fukuoka, Japan |
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Abstract: | Summary The nucleotide sequences of the recessivednaQ49 and the dominantmutD5 mutator were determined. ThednaQ49 mutator has a single base substitution in thednaQ gene, thus causing one amino acid change,96Val (GTG)→ Gly (GGG), in the DnaQ protein (ε subunit of DNA polymerase III holoenzyme). ThemutD5 mutator possesses two base substitutions in the same gene, resulting in two amino acid changes,73Leu (TTG)→Trp (TGG) and164Ala (GCA)→Val (GTA), which were designated themutD52 andmutD51 mutations, respectively. Construction of chimaeric genes carrying one or two of these mutations revealed: (1) eithermutD51 ormutD52 alone causes the dominant mutator phenotype when present in a multi-copy plasmid; (2)mutD51, but notmutD52, exerts the dominant mutator phenotype when present in a low-copy plasmid; (3) the dominantmutD51 mutator activity is suppressed by thednaQ49 mutation when both mutations are present in the same gene. Based on these findings, we devised a model for the action of
these mutators. |
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Keywords: | Mutator DNA polymerase III dnaQ gene Suppression |
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