Lesburg C A, Cable M B, Ferrari E, Hong Z, Mannarino A F, Weber P C
Department of Structural Chemistry, Schering-Plough Research Institute, Kenilworth, New Jersey 07033, USA.
Nat Struct Biol. 1999 Oct;6(10):937-43. doi: 10.1038/13305.
Various classes of nucleotidyl polymerases with different transcriptional roles contain a conserved core structure. Less is known, however, about the distinguishing features of these enzymes, particularly those of the RNA-dependent RNA polymerase class. The 1. 9 A resolution crystal structure of hepatitis C virus (HCV) nonstructural protein 5B (NS5B) presented here provides the first complete and detailed view of an RNA-dependent RNA polymerase. While canonical polymerase features exist in the structure, NS5B adopts a unique shape due to extensive interactions between the fingers and thumb polymerase subdomains that serve to encircle the enzyme active site. Several insertions in the fingers subdomain account for intersubdomain linkages that include two extended loops and a pair of antiparallel alpha-helices. The HCV NS5B apoenzyme structure reported here can accommodate a template:primer duplex without global conformational changes, supporting the hypothesis that this structure is essentially preserved during the reaction pathway. This NS5B template:primer model also allows identification of a new structural motif involved in stabilizing the nascent base pair.
具有不同转录作用的各类核苷酸聚合酶都含有一个保守的核心结构。然而，对于这些酶的独特特征，尤其是依赖RNA的RNA聚合酶类的特征，人们了解得较少。本文展示的丙型肝炎病毒（HCV）非结构蛋白5B（NS5B）的晶体结构分辨率为1.9埃，首次提供了依赖RNA的RNA聚合酶完整而详细的视图。虽然该结构中存在典型的聚合酶特征，但由于手指和拇指聚合酶亚结构域之间广泛的相互作用，NS5B呈现出独特的形状，这些相互作用环绕着酶的活性位点。手指亚结构域中的几个插入片段构成了亚结构域间的连接，包括两个延伸环和一对反平行的α螺旋。此处报道的HCV NS5B无酶蛋白结构可以容纳模板：引物双链体而无需全局构象变化，支持了该结构在反应途径中基本保持不变的假设。这个NS5B模板：引物模型还允许识别一个参与稳定新生碱基对的新结构基序。
