Joseph J W, Kolodner R
J Biol Chem. 1983 Sep 10;258(17):10411-7.
Exonuclease VIII is an enzyme whose synthesis is induced as a result of sbcA mutations. The enzyme has been purified to near homogeneity from an Escherichia coli strain containing an sbcA mutation and mutations in the structural genes for exonuclease III, exonuclease V, and endonuclease I. The enzyme specifically degrades linear duplex DNA in a reaction which requires magnesium ions and is susceptible to inhibition by other divalent cations and by sulfhydryl-blocking reagents. Enzyme activity occurs over a broad pH range with peak activity at pH 8.5 in Tris buffer. The protein has a subunit Mr = 140,000, a sedimentation coefficient of 8.4 +/- 0.6, and a Stokes radius of 142 +/- 6 A, which is consistent with its active form being a multimer. Exonuclease VIII has a frictional coefficient of 2.6 which indicates that it has an asymmetric structure.
外切核酸酶VIII是一种因sbcA突变而诱导合成的酶。该酶已从一株含有sbcA突变以及外切核酸酶III、外切核酸酶V和内切核酸酶I结构基因突变的大肠杆菌菌株中纯化至近乎同质。该酶在需要镁离子的反应中特异性降解线性双链DNA，并且易受其他二价阳离子和巯基封闭试剂的抑制。酶活性在较宽的pH范围内出现，在Tris缓冲液中pH 8.5时活性最高。该蛋白质的亚基分子量为140,000，沉降系数为8.4 +/- 0.6，斯托克斯半径为142 +/- 6 Å，这与其活性形式为多聚体一致。外切核酸酶VIII的摩擦系数为2.6，表明它具有不对称结构。
