Berman Andrea J, Kamtekar Satwik, Goodman Jessica L, Lázaro José M, de Vega Miguel, Blanco Luis, Salas Margarita, Steitz Thomas A
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA.
EMBO J. 2007 Jul 25;26(14):3494-505. doi: 10.1038/sj.emboj.7601780. Epub 2007 Jul 5.
Replicative DNA polymerases (DNAPs) move along template DNA in a processive manner. The structural basis of the mechanism of translocation has been better studied in the A-family of polymerases than in the B-family of replicative polymerases. To address this issue, we have determined the X-ray crystal structures of phi29 DNAP, a member of the protein-primed subgroup of the B-family of polymerases, complexed with primer-template DNA in the presence or absence of the incoming nucleoside triphosphate, the pre- and post-translocated states, respectively. Comparison of these structures reveals a mechanism of translocation that appears to be facilitated by the coordinated movement of two conserved tyrosine residues into the insertion site. This differs from the mechanism employed by the A-family polymerases, in which a conserved tyrosine moves into the templating and insertion sites during the translocation step. Polymerases from the two families also interact with downstream single-stranded template DNA in very different ways.
复制性DNA聚合酶（DNAPs）以持续合成的方式沿着模板DNA移动。与复制性聚合酶的B家族相比，聚合酶A家族中易位机制的结构基础得到了更好的研究。为了解决这个问题，我们确定了phi29 DNAP的X射线晶体结构，它是聚合酶B家族中蛋白质引发亚组的成员，分别在存在或不存在即将进入的核苷三磷酸的情况下与引物-模板DNA复合，即易位前和易位后的状态。这些结构的比较揭示了一种易位机制，该机制似乎是由两个保守的酪氨酸残基协同移动到插入位点所促进的。这与A家族聚合酶采用的机制不同，在A家族聚合酶中，一个保守的酪氨酸在易位步骤中移动到模板和插入位点。这两个家族的聚合酶与下游单链模板DNA的相互作用方式也非常不同。
