The structure of the poliovirus 135S cell entry intermediate at 10-Angstrom resolution reveals the location of an externalized polypeptide that binds to membranes
The structure of the poliovirus 135S cell entry intermediate at 10-Angstrom resolution reveals the location of an externalized polypeptide that binds to membranes
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DOI：
10.1128/jvi.79.12.7745-7755.2005
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发表时间：
2005-06-01
影响因子：
5.4
通讯作者：
Belnap, DM
中科院分区：
文献类型：
--
作者：
Bubeck, D;Filman, DJ;Belnap, DM
脊髓灰质炎病毒为了解无包膜病毒如何进入和感染细胞提供了一个特征明确的系统。脊髓灰质炎病毒一旦与其受体结合，就会经历不可逆转的构象变化，变成135S进入细胞的中间体。这种转变涉及衣壳蛋白0桶的移动，伴随着VP4和V-P1的N端的外化。这两种多肽都与膜结合，并被认为通过为病毒RNA形成易位孔来促进进入。我们计算了135S粒子的冷冻电子显微镜重建，允许准确放置衣壳蛋白的0桶、环和末端延伸。重建和由此产生的模型表明，VP1的每个N端通过围绕五重轴的峡谷底部VP1和VP3之间的界面上的一个开口离开衣壳。与蛋白质水解法去除VP1前31个残基的135S粒子的重建相比，外化的N末端位于围绕三重轴的螺旋桨样特征的末端附近，而不是像以前的模型所提出的那样位于五重轴上。这些观察结果迫使人们重新审视目前关于135S粒子在跨膜孔形成中的作用的模型，并提出了可测试的替代方案。
Poliovirus provides a well-characterized system for understanding how nonenveloped viruses enter and infect cells. Upon binding its receptor, poliovirus undergoes an irreversible conformational change to the 135S cell entry intermediate. This transition involves shifts of the capsid protein 0 barrels, accompanied by the externalization of VP4 and the N terminus of V-P1. Both polypeptides associate with membranes and are postulated to facilitate entry by forming a translocation pore for the viral RNA. We have calculated cryoelectron microscopic reconstructions of 135S particles that permit accurate placement of the 0 barrels, loops, and terminal extensions of the capsid proteins. The reconstructions and resulting models indicate that each N terminus of VP1 exits the capsid though an opening in the interface between VP1 and VP3 at the base of the canyon that surrounds the fivefold axis. Comparison with reconstructions of 135S particles in which the first 31 residues of VP1 were proteolytically removed revealed that the externalized N terminus is located near the tips of propeller-like features surrounding the threefold axes rather than at the fivefold axes, as had been proposed in previous models. These observations have forced a reexamination of current models for the role of the 135S particle in transmembrane pore formation and suggest testable alternatives.