Barnes M H, Leo C J, Brown N C
Department of Pharmacology and Molecular Toxicology, University of Massachusetts Medical School, Worcester 01655-0126, USA.
Biochemistry. 1998 Nov 3;37(44):15254-60. doi: 10.1021/bi981113m.
DNA polymerase III (pol III) of Gram-positive eubacteria is a catalytically bifunctional DNA polymerase:3'-5' exonuclease [Low, R. L., Rashbaum, S. A., and Cozzarelli, N. R. (1976) J. Biol.Chem. 251, 1311-1325]. The pol III protein conserves, between its exonuclease and dNTP binding sites, a 35-residue segment of primary structure with the potential to form a zinc finger-like structure [Berg, J. M. (1990) Ann. Rev. Biochem. 19, 405-421]. This paper describes results of experiments which probe the capacity of this segment to bind zinc and the role of this segment in enzyme function. The results of metal and mutational analysis of a model pol III derived from Bacillus subtilis indicate that (i) the Gram-positive pol III is a metalloprotein containing tightly bound zinc in a stoichiometry of 1, (ii) the zinc atom is bound within the 35-residue segment, likely in one of two probable finger-like structures, and (iii) the integrity of the zinc-bound structure is specifically critical to the formation and/or function of the enzyme's polymerase site.
革兰氏阳性真细菌的DNA聚合酶III（pol III）是一种具有催化双功能的DNA聚合酶：3'-5'核酸外切酶[洛，R.L.，拉什鲍姆，S.A.，和科扎雷利，N.R.（1976年）《生物化学杂志》251，1311 - 1325]。pol III蛋白在其核酸外切酶和dNTP结合位点之间保留了一段35个残基的一级结构片段，该片段有可能形成类似锌指的结构[伯格，J.M.（1990年）《生物化学年度评论》19，405 - 421]。本文描述了一些实验结果，这些实验探究了该片段结合锌的能力以及该片段在酶功能中的作用。对源自枯草芽孢杆菌的模型pol III进行金属和突变分析的结果表明：（i）革兰氏阳性pol III是一种金属蛋白，含有化学计量比为1的紧密结合的锌；（ii）锌原子结合在35个残基的片段内，可能存在于两种可能的类似指状结构之一中；（iii）锌结合结构的完整性对酶的聚合酶位点的形成和/或功能特别关键。
