Structure of a bifunctional DNA primase-polymerase
Structure of a bifunctional DNA primase-polymerase
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DOI：
10.1038/nsmb723
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发表时间：
2004-02-01
影响因子：
16.8
通讯作者：
Cramer, P
中科院分区：
文献类型：
--
作者：
Lipps, G;Weinzierl, AO;Cramer, P
基因组复制通常需要合成初始寡核苷酸引物的引物酶和延长引物的DNA聚合酶。然而，在新鉴定的来自古细菌质粒的复制酶中，例如来自冰岛硫化叶菌的pRN 1中，引物酶和DNA聚合酶活性是组合的。在这里，我们提出了一个pRN 1引物聚合酶（prim-pol）结构域的结构-功能分析。晶体结构显示由保守残基排列的中心凹陷。凹陷一侧的突变会降低DNA亲和力。在凹陷的另一侧聚集了三个酸性残基和一个组氨酸，这是引发酶和DNA聚合酶活性所必需的。一个酸性残基结合锰离子，暗示金属依赖性催化机制。其结构与DNA聚合酶没有任何相似性，但与古细菌和真核生物的引物酶有较远的关系，具有相应的活性位点残基。我们认为古细菌和真核生物的引物酶和引物聚合酶结构域有一个共同的进化祖先，一个小DNA基因组的双功能复制酶。
Genome replication generally requires primases, which synthesize an initial oligonucleotide primer, and DNA polymerases, which elongate the primer. Primase and DNA polymerase activities are combined, however, in newly identified replicases from archaeal plasmids, such as pRN1 from Sulfolobus islandicus. Here we present a structure-function analysis of the pRN1 primase-polymerase (prim-pol) domain. The crystal structure shows a central depression lined by conserved residues. Mutations on one side of the depression reduce DNA affinity. On the opposite side of the depression cluster three acidic residues and a histidine, which are required for primase and DNA polymerase activity. One acidic residue binds a manganese ion, suggestive of a metal-dependent catalytic mechanism. The structure does not show any similarity to DNA polymerases, but is distantly related to archaeal and eukaryotic primases, with corresponding active-site residues. We propose that archaeal and eukaryotic primases and the prim-pol domain have a common evolutionary ancestor, a bifunctional replicase for small DNA genomes.