Kelly W S, Grindley N D
Nucleic Acids Res. 1976 Nov;3(11):2971-84. doi: 10.1093/nar/3.11.2971.
The polA6 mutation is an allele of the polA gene of Escherichia coli which produces a DNA polymerase I species readily distinguishable from that produced by the wild type allele. Experiments described here show that this enzyme has an altered pH optimum for polymerization and a lower binding affinity for DNA. The defect clearly lies within the carboxyl-terminal large fragment of the enzyme produced by in vivo or in vitro proteolysis since the fragment has the same pH optimum for polymerization as the intact enzyme. The polA6 enzyme and its fragment are more sensitive to phosphate ions than the wild type polymerase, and the large fragment is less efficient at binding poly d(AT) in in vitro binding assays. Although the specific nucleolytic activity of the polA6 enzyme is higher than that of the wild type, there is no apparent alteration in pH optimum for the hydrolysis of eigher double or single stranded DNA.
polA6突变是大肠杆菌polA基因的一个等位基因，它产生的DNA聚合酶I与野生型等位基因产生的DNA聚合酶I很容易区分。这里描述的实验表明，这种酶的聚合作用的最适pH值发生了改变，并且对DNA的结合亲和力较低。由于该片段与完整酶具有相同的聚合最适pH值，所以缺陷显然存在于体内或体外蛋白水解产生的酶的羧基末端大片段内。与野生型聚合酶相比，polA6酶及其片段对磷酸根离子更敏感，并且在体外结合试验中，大片段结合聚d(AT)的效率较低。尽管polA6酶的特异性核酸水解活性高于野生型，但无论是双链还是单链DNA水解的最适pH值都没有明显改变。
