Huiskonen Juha T, Jäälinoja Harri T, Briggs John A G, Fuller Stephen D, Butcher Sarah J
Institute of Biotechnology and Faculty of Biosciences, University of Helsinki, P.O. Box 65 (Viikinkaari 1), FI-00014 University of Helsinki, Finland.
J Struct Biol. 2007 May;158(2):156-64. doi: 10.1016/j.jsb.2006.08.021. Epub 2006 Oct 7.
Packaging of the Cystovirus varphi8 genome into the polymerase complex is catalysed by the hexameric P4 packaging motor. The motor is located at the fivefold vertices of the icosahedrally symmetric polymerase complex, and the symmetry mismatch between them may be critical for function. We have developed a novel image-processing approach for the analysis of symmetry-mismatched structures and applied it to cryo-electron microscopy images of P4 bound to the polymerase complex. This approach allowed us to solve the three-dimensional structure of the P4 in situ to 15-A resolution. The C-terminal face of P4 was observed to interact with the polymerase complex, supporting the current view on RNA translocation. We suggest that the symmetry mismatch between the two components may facilitate the ring opening required for RNA loading prior to its translocation.
噬菌体φ8基因组包装到聚合酶复合物中是由六聚体P4包装马达催化的。该马达位于二十面体对称聚合酶复合物的五重顶点，它们之间的对称性不匹配可能对功能至关重要。我们开发了一种用于分析对称性不匹配结构的新型图像处理方法，并将其应用于与聚合酶复合物结合的P4的冷冻电子显微镜图像。这种方法使我们能够原位解析P4的三维结构，分辨率达到15埃。观察到P4的C末端面与聚合酶复合物相互作用，支持了目前关于RNA转运的观点。我们认为，这两个组件之间的对称性不匹配可能有助于在RNA转运之前加载RNA所需的环打开。
