Morais Marc C, Kanamaru Shuji, Badasso Mohammed O, Koti Jaya S, Owen Barbara A L, McMurray Cynthia T, Anderson Dwight L, Rossmann Michael G
Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, Indiana 47907-2054, USA.
Nat Struct Biol. 2003 Jul;10(7):572-6. doi: 10.1038/nsb939.
Three-dimensional structures of the double-stranded DNA bacteriophage phi29 scaffolding protein (gp7) before and after prohead assembly have been determined at resolutions of 2.2 and 2.8 A, respectively. Both structures are dimers that resemble arrows, with a four-helix bundle composing the arrowhead and a coiled coil forming the tail. The structural resemblance of gp7 to the yeast transcription factor GCN4 suggests a DNA-binding function that was confirmed by native gel electrophoresis. DNA binding to gp7 may have a role in mediating the structural transition from prohead to mature virus and scaffold release. A cryo-EM analysis indicates that gp7 is arranged inside the capsid as a series of concentric shells. The position of the higher density features in these shells correlates with the positions of hexamers in the equatorial region of the capsid, suggesting that gp7 may regulate formation of the prolate head through interactions with these hexamers.
双链DNA噬菌体phi29支架蛋白（gp7）在原头部组装前后的三维结构分别以2.2埃和2.8埃的分辨率确定。这两种结构均为二聚体，形似箭头，由一个四螺旋束构成箭头，一个卷曲螺旋形成尾部。gp7与酵母转录因子GCN4的结构相似性表明其具有DNA结合功能，这一点通过非变性凝胶电泳得到了证实。DNA与gp7的结合可能在介导从原头部到成熟病毒的结构转变以及支架释放中发挥作用。冷冻电镜分析表明，gp7在衣壳内部排列成一系列同心壳层。这些壳层中较高密度特征的位置与衣壳赤道区域六聚体的位置相关，这表明gp7可能通过与这些六聚体的相互作用来调节长形头部的形成。
