Dube D K, Kunkel T A, Seal G, Loeb L A
Biochim Biophys Acta. 1979 Feb 27;561(2):369-82. doi: 10.1016/0005-2787(79)90145-x.
DNA polymerase-alpha and -beta can be distinguished from one another by the differential effects of N-ethylmaleimide, KCl, ara-CTP and temperature, as well as on the basis of sedimentation. The sensitivity of DNA polymerase-beta to elevated temperatures as compared to DNA polymerase-alpha provides a new means of distinguishing between these two enzymes even in crude extracts and a possible probe for determining their function. DNA polymerase-alpha and -beta share several properties in common, including the ability to readily incorporate dUTP in place of dTTP. The Km for dUTP varies from 10 to 30 micron with different preparations of DNA polymerase-alpha and -beta. Thus, in mammalian cells, dUMP could be incorporated into DNA, and if excised by an endonuclease, would lead to discontinuities. Initial analyses of fidelity in direct comparative studies indicate that beta-class DNA polymerases are highly accurate in base selection when copying poly[d(A-T)]. Less than one molecule of dGMP is incorporated for every 12 000-45 000 molecules of dAMP and dTMP polymerized. DNA polymerase-alpha is somewhat less accurate, making one mistake for every 4000-10 000 correct nucleotides incorporated. Since both polymerases lack an exonucleolytic activity, this accuracy must be the result of selectivity for the complementary nucleotide by the polymerase.
DNA聚合酶α和β可以通过N-乙基马来酰亚胺、氯化钾、阿糖胞苷三磷酸和温度的不同影响以及沉降情况相互区分。与DNA聚合酶α相比，DNA聚合酶β对高温更敏感，这为区分这两种酶提供了一种新方法，即使在粗提物中也是如此，并且可能是确定它们功能的一种探针。DNA聚合酶α和β有几个共同特性，包括能够轻易地掺入dUTP来取代dTTP。不同制备的DNA聚合酶α和β对dUTP的米氏常数在10至30微摩尔之间变化。因此，在哺乳动物细胞中，dUMP可能掺入DNA中，如果被核酸内切酶切除，会导致DNA不连续。直接比较研究中对保真度的初步分析表明，β类DNA聚合酶在复制聚[d(A-T)]时碱基选择高度准确。每聚合12000 - 45000个dAMP和dTMP分子，掺入的dGMP分子不到一个。DNA聚合酶α的准确性稍低，每掺入4000 - 10000个正确核苷酸会出现一个错误。由于这两种聚合酶都缺乏核酸外切酶活性，这种准确性必定是聚合酶对互补核苷酸选择性的结果。
