Byrnes J J, Downey K M, Black V L, So A G
Biochemistry. 1976 Jun 29;15(13):2817-23. doi: 10.1021/bi00658a018.
A new species of DNA polymerase has been purified more than 10 000-fold from the cytoplasm of erythroid hyperplastic bone marrow. This DNA polymerase, in contrast to previously described eukaryotic DNA polymerases, is associated with a very active 3' to 5' exonuclease activity. Similar to the 3' to 5' exonuclease activity associated with prokaryotic DNA polymerases, this enzyme catalyzes the removal of 3'-terminal nucleotides from DNA, as well as a template-dependent conversion of deoxyribonucleoside triphosphates to monophosphates. The exonuclease activity is not separable from the DNA polymerase activity by chromatography on DEAE-Sephadex or hydroxylapatite, and upon sucrose density gradient centrifugation the two activities cosediment at 7 S or at 11 S depending on the ionic strength. Both exonuclease and polymerase activities have identical rates of heat inactivation and both are equally sensitive to hemin and Rifamycin AF/013, inhibitors of DNA synthesis that act by binding to DNA polymerase and causing its dissociation from its template/primer. These results are consistent with the coexistence of two enzyme activities in a single protein.
一种新的DNA聚合酶已从红细胞增生性骨髓的细胞质中纯化出来，纯化倍数超过10000倍。与先前描述的真核生物DNA聚合酶不同，这种DNA聚合酶与一种非常活跃的3'至5'核酸外切酶活性相关。与原核生物DNA聚合酶相关的3'至5'核酸外切酶活性类似，这种酶催化从DNA中去除3'末端核苷酸，以及将脱氧核糖核苷三磷酸模板依赖性转化为单磷酸。通过DEAE-葡聚糖凝胶或羟基磷灰石柱层析，核酸外切酶活性与DNA聚合酶活性不可分离，在蔗糖密度梯度离心中，根据离子强度，两种活性在7S或11S处共同沉降。核酸外切酶和聚合酶活性具有相同的热失活速率，并且对血红素和利福霉素AF/013同样敏感，这两种DNA合成抑制剂通过与DNA聚合酶结合并使其从模板/引物上解离而起作用。这些结果与两种酶活性共存于单一蛋白质中一致。
