Garmendia C, Bernad A, Esteban J A, Blanco L, Salas M
Centro de Biología Molecular (Consejo Superior de Investigacìones Científicas-UAM), Universidad Autónoma, Madrid, Spain.
J Biol Chem. 1992 Feb 5;267(4):2594-9.
The bacteriophage phi 29 DNA polymerase, involved both in the protein-primed initiation and elongation steps of the viral DNA replication, displays a very processive 3',5'-exonuclease activity acting preferentially on single-stranded DNA. This exonucleolytic activity showed a marked preference for excision of a mismatched versus a correctly paired 3' terminus. These characteristics enable the phi 29 DNA polymerase to act as a proofreading enzyme. A comparative analysis of the wild-type phi 29 DNA polymerase and a mutant lacking 3',5'-exonuclease activity indicated that a productive coupling between the exonuclease and polymerase activities is necessary to prevent fixation of polymerization errors. Based on these data, the phi 29 DNA polymerase, a model enzyme for protein-primed DNA replication, appears to share the same mechanism for the editing function as that first proposed for T4 DNA polymerase and Escherichia coli DNA polymerase I on the basis of functional and structural studies.
噬菌体φ29 DNA聚合酶参与病毒DNA复制的蛋白质引发起始和延伸步骤，具有很强的3',5'-核酸外切酶活性，优先作用于单链DNA。这种核酸外切酶活性对切除错配的3'末端比对正确配对的3'末端有明显偏好。这些特性使φ29 DNA聚合酶能够作为校对酶发挥作用。对野生型φ29 DNA聚合酶和缺乏3',5'-核酸外切酶活性的突变体进行的比较分析表明，核酸外切酶活性和聚合酶活性之间的有效偶联对于防止聚合错误的固定是必要的。基于这些数据，φ29 DNA聚合酶作为蛋白质引发DNA复制的模型酶，似乎与基于功能和结构研究首次提出的T4 DNA聚合酶和大肠杆菌DNA聚合酶I具有相同的编辑功能机制。
