Seal G, Loeb L A
J Biol Chem. 1976 Feb 25;251(4):975-81.
DNA polymerase from RNA tumor viruses ("reverse transcriptase") has been analyzed for activities which have been associated with other DNA polymerases. Homogeneous DNA polymerase from avian myeoblastosis virus catalyzes pyrophosphate exchange and pyrophosphorolysis. Pyrophosphate exchange is dependent on a template and is base-specific. With avian myeloblastosis virus DNA polymerase, ribonucleotide templates are more efficient for synthesis while deoxyribonucleotide templates are more effective for pyrophosphate exchange. Synthesis, pyrophosphate exchange, and pyrophosphorolysis were inhibited by the chelating agent 1,10-phenanthroline, suggesting that enzyme-bound zinc is required for each of these reactions. The pyrophosphate exchange reaction was also demonstrated with the DNA polymerase from a mutant of Rous sarcoma virus that possesses a temperature-sensitive DNA polymerase. The pyrophosphate exchange reaction with the mutant polymerase is temperature-sensitive which demonstrates that pyrophosphate exchange is indeed catalyzed by the viral DNA polymerase and that the same mutation effects both DNA polymerase and pyrophosphatase activity. Unlike Escherichia coli DNA polymerase I, the DNA polymerase from avian myeloblastosis virus fails to degrade polydeoxyribonucleotides or to convert deoxynucleoside triphosphates into monophosphates. This lack of hydrolytic activities in avian myeoblastosis DNA polymerase should facilitate kinetic studies on the mechanism of DNA synthesis by this enzyme.
对来自RNA肿瘤病毒的DNA聚合酶（“逆转录酶”）进行了分析，以研究其与其他DNA聚合酶相关的活性。来自禽成髓细胞瘤病毒的纯一DNA聚合酶催化焦磷酸交换和焦磷酸解。焦磷酸交换依赖于模板且具有碱基特异性。对于禽成髓细胞瘤病毒DNA聚合酶，核糖核苷酸模板对合成更有效，而脱氧核糖核苷酸模板对焦磷酸交换更有效。螯合剂1,10 - 菲咯啉抑制了合成、焦磷酸交换和焦磷酸解，这表明这些反应中的每一个都需要酶结合的锌。来自劳斯肉瘤病毒突变体的DNA聚合酶也证明了焦磷酸交换反应，该突变体具有温度敏感型DNA聚合酶。突变体聚合酶的焦磷酸交换反应是温度敏感的，这表明焦磷酸交换确实是由病毒DNA聚合酶催化的，并且相同的突变影响DNA聚合酶和焦磷酸酶活性。与大肠杆菌DNA聚合酶I不同，来自禽成髓细胞瘤病毒的DNA聚合酶不能降解多脱氧核糖核苷酸或将脱氧核苷三磷酸转化为单磷酸。禽成髓细胞瘤DNA聚合酶缺乏这种水解活性，这将有助于对该酶的DNA合成机制进行动力学研究。
