Fokine Andrei, Rossmann Michael G
Department of Biological Sciences, Hockmeyer Hall of Structural Biology, Purdue University, 240 South Martin Jischke Drive, West Lafayette, IN 47907, USA.
Structure. 2016 Nov 1;24(11):1928-1935. doi: 10.1016/j.str.2016.08.013. Epub 2016 Sep 22.
Many large viruses, including tailed dsDNA bacteriophages and herpesviruses, assemble their capsids via formation of precursors, called procapsids or proheads. The prohead has an internal core, made of scaffolding proteins, and an outer shell, formed by the major capsid protein. The prohead usually contains a protease, which is activated during capsid maturation to destroy the inner core and liberate space for the genome. Here, we report a 2.0 Å resolution structure of the pentameric procapsid protease of bacteriophage T4, gene product (gp)21. The structure corresponds to the enzyme's pre-active state in which its N-terminal region blocks the catalytic center, demonstrating that the activation mechanism involves self-cleavage of nine N-terminal residues. We describe similarities and differences between T4 gp21 and related herpesvirus proteases. We found that gp21 and the herpesvirus proteases have similarity with proteins forming the tubes of phage tails and bacterial type VI secretion systems, suggesting their common evolutionary origin.
许多大型病毒，包括有尾双链DNA噬菌体和疱疹病毒，通过形成称为前衣壳或原头部的前体来组装它们的衣壳。前头部有一个由支架蛋白构成的内部核心和一个由主要衣壳蛋白形成的外壳。前头部通常含有一种蛋白酶，该蛋白酶在衣壳成熟过程中被激活，以破坏内部核心并为基因组释放空间。在此，我们报道了噬菌体T4的五聚体前衣壳蛋白酶基因产物（gp）21的分辨率为2.0 Å的结构。该结构对应于酶的前活性状态，其中其N端区域阻断催化中心，表明激活机制涉及九个N端残基的自我切割。我们描述了T4 gp21与相关疱疹病毒蛋白酶之间的异同。我们发现gp21和疱疹病毒蛋白酶与形成噬菌体尾部管和细菌VI型分泌系统的蛋白质具有相似性，表明它们有共同的进化起源。
