The highly conserved amino acid sequence motif Tyr-Gly-Asp-Thr-Asp-Ser in alpha-like DNA polymerases is required by phage phi 29 DNA polymerase for protein-primed initiation and polymerization.

The alpha-like DNA polymerases from bacteriophage phi 29 and other viruses, prokaryotes and eukaryotes contain an amino acid consensus sequence that has been proposed to form part of the dNTP binding site. We have used site-directed mutants to study five of the six highly conserved consecutive amino acids corresponding to the most conserved C-terminal segment (Tyr-Gly-Asp-Thr-Asp-Ser). Our results indicate that in phi 29 DNA polymerase this consensus sequence, although irrelevant for the 3'----5' exonuclease activity, is essential for initiation and elongation. Based on these results and on its homology with known or putative metal-binding amino acid sequences, we propose that in phi 29 DNA polymerase the Tyr-Gly-Asp-Thr-Asp-Ser consensus motif is part of the dNTP binding site, involved in the synthetic activities of the polymerase (i.e., initiation and polymerization), and that it is involved particularly in the metal binding associated with the dNTP site. IMAGES:

来自噬菌体Φ29及其他病毒、原核生物与真核生物的类αDNA聚合酶（alpha-like DNA polymerases）含有一段氨基酸共有序列，该序列被推测为脱氧核苷三磷酸（dNTP）结合位点的组成部分。我们借助定点突变体（site-directed mutants），对对应于最保守C端区段（Tyr-Gly-Asp-Thr-Asp-Ser）的6个高度保守连续氨基酸残基中的5个进行了研究。结果显示，在Φ29 DNA聚合酶中，该共有序列虽与3'→5'核酸外切酶活性无关，但对聚合反应的起始与延伸过程至关重要。基于上述研究结果，以及该序列与已知或推定的金属结合氨基酸序列的同源性，我们提出：在Φ29 DNA聚合酶中，Tyr-Gly-Asp-Thr-Asp-Ser共有基序是dNTP结合位点的组成部分，参与聚合酶的合成活性（即起始与聚合过程），且尤其参与与dNTP位点相关的金属结合过程。图像：