Tsurudome Masato
Department of Microbiology, Mie University Graduate School of Medicine, Tsu, Mie, Japan.
Uirusu. 2005 Dec;55(2):207-19. doi: 10.2222/jsv.55.207.
The majority of viral fusion proteins can be divided into two classes. The influenza hemagglutinin (HA) belongs to the class I fusion proteins and undergoes a series of conformational changes at acidic pH, leading to membrane fusion. The crystal structures of the prefusion and the postfusion forms of HA have been revealed in 1981 and 1994, respectively. On the basis of these structures, a model for the mechanism of membrane fusion mediated by the conformational changes of HA has been proposed. The flavivirus E and alphavirus E1 proteins belong to the class II fusion proteins and mediate membrane fusion at acidic pH. Their prefusion structures are distinct from that of HA. Last year, however, it has become evident that the postfusion structures of these class I and class II fusion proteins are similar. The paramyxovirus F protein belongs to the class I fusion proteins. In contrast to HA, an interaction between F and its homologous attachment protein is required for F to undergo the conformational changes. Since F mediates fusion at neutral pH, the infected cells can fuse with neighboring uninfected cells. The crystal structures of F and the attachment protein HN have recently been clarified, which will facilitate studies of the molecular mechanism of F-mediated membrane fusion.
大多数病毒融合蛋白可分为两类。流感血凝素（HA）属于I类融合蛋白，在酸性pH条件下会经历一系列构象变化，从而导致膜融合。HA的融合前和融合后形式的晶体结构分别于1981年和1994年被揭示。基于这些结构，已经提出了一个由HA构象变化介导的膜融合机制模型。黄病毒E蛋白和甲病毒E1蛋白属于II类融合蛋白，在酸性pH条件下介导膜融合。它们的融合前结构与HA不同。然而，去年已经很明显，这些I类和II类融合蛋白的融合后结构是相似的。副粘病毒F蛋白属于I类融合蛋白。与HA不同，F蛋白要发生构象变化需要F与其同源附着蛋白之间相互作用。由于F在中性pH条件下介导融合，受感染细胞可以与相邻未感染细胞融合。F蛋白和附着蛋白HN的晶体结构最近已经阐明，这将有助于对F介导的膜融合分子机制的研究。
