Wang Ganggang, Klein Michael G, Tokonzaba Etienne, Zhang Yi, Holden Lauren G, Chen Xiaojiang S
Molecular and Computational Biology, University of Southern California, 1050 Childs Way, Los Angeles, California 90089, USA.
Nat Struct Mol Biol. 2008 Jan;15(1):94-100. doi: 10.1038/nsmb1356. Epub 2007 Dec 23.
Helicases are essential enzymes for DNA replication, a fundamental process in all living organisms. The DnaB family are hexameric replicative helicases that unwind duplex DNA and coordinate with RNA primase and other proteins at the replication fork in prokaryotes. Here, we report the full-length crystal structure of G40P, a DnaB family helicase. The hexamer complex reveals an unusual architectural feature and a new type of assembly mechanism. The hexamer has two tiers: a three-fold symmetric N-terminal tier and a six-fold symmetric C-terminal tier. Monomers with two different conformations, termed cis and trans, come together to provide a topological solution for the dual symmetry within a hexamer. Structure-guided mutational studies indicate an important role for the N-terminal tier in binding primase and regulating primase-mediated stimulation of helicase activity. This study provides insights into the structural and functional interplay between G40P helicase and DnaG primase.
解旋酶是DNA复制所必需的酶，而DNA复制是所有生物体中的一个基本过程。DnaB家族是六聚体复制解旋酶，可解开双链DNA，并在原核生物的复制叉处与RNA引物酶及其他蛋白质协同作用。在此，我们报道了DnaB家族解旋酶G40P的全长晶体结构。该六聚体复合物揭示了一种不同寻常的结构特征和一种新型的组装机制。六聚体有两层：一个三重对称的N端层和一个六重对称的C端层。具有两种不同构象（称为顺式和反式）的单体聚集在一起，为六聚体内的双重对称性提供了一种拓扑学解决方案。基于结构的突变研究表明，N端层在结合引物酶和调节引物酶介导的解旋酶活性刺激方面发挥着重要作用。这项研究为G40P解旋酶与DnaG引物酶之间的结构和功能相互作用提供了见解。
