Hepatitis C virus glycoprotein E2 contains a membrane-proximal heptad repeat sequence that is essential for E1E2 glycoprotein heterodimerization and viral entry
Hepatitis C virus glycoprotein E2 contains a membrane-proximal heptad repeat sequence that is essential for E1E2 glycoprotein heterodimerization and viral entry
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DOI：
10.1074/jbc.m405098200
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发表时间：
2004-07-16
影响因子：
4.8
通讯作者：
Poumbourios, P
中科院分区：
文献类型：
--
作者：
Drummer, HE;Poumbourios, P
丙型肝炎病毒的E1和E2糖蛋白形成非共价缔合的异源二聚体，介导病毒进入。糖蛋白E2包含受体结合结构域（残基384-661），其通过含有疏水性七肽重复序列（残基675-699）的高度保守序列连接至跨膜结构域（残基716-746）。E2七肽重复序列的丙氨酸和脯氨酸扫描诱变显示Leu（675）、Ser（678）、Leu（689）和Leu（692）对于E1 E2异源二聚化是重要的。此外，除了一个七肽重复残基（Ser（678））之外的所有七肽重复残基的Pro和Ala取代阻断了E1 E2-HIV-1假型进入Huh 7细胞，而不管对异源二聚化的影响。两个保守的脯氨酸（Pro（676）和Pro（683）），占据七肽的连续B位置，不需要E1 E2异源二聚化;然而，Pro（683）是病毒进入的关键。因此，破坏预测的α-螺旋结构的脯氨酸在位置683是重要的E2功能。突变体不能介导病毒进入不能解释为受体结合功能的丧失，因为所有突变体都能够与重组形式的CD 81大细胞外环相互作用。黄病毒prM和E糖蛋白的E1和E2胞外结构域和跨膜结构域之间分别形成的嵌合体能够异源二聚化，尽管与野生型E1 E2相比效率较低。因此，E2的七肽重复序列需要天然跨膜结构域用于完全异源二聚化和病毒进入功能。我们的数据表明，E2的膜近端七肽重复功能同源的黄病毒E糖蛋白的茎。我们建议，E2与II类融合蛋白具有共同的机制特征。
The E1 and E2 glycoproteins of hepatitis C virus form a noncovalently associated heterodimer that mediates viral entry. Glycoprotein E2 comprises a receptor-binding domain (residues 384-661) that is connected to the transmembrane domain (residues 716-746) via a highly conserved sequence containing a hydrophobic heptad repeat (residues 675-699). Alanine- and proline-scanning mutagenesis of the E2 heptad repeat revealed that Leu(675), Ser(678), Leu(689), and Leu(692) are important for E1E2 heterodimerization. Furthermore, Pro and Ala substitution of all but one heptad repeat residue (Ser(678)) blocked the entry of E1E2-HIV-1 pseudotypes into Huh7 cells, irrespective of an effect on heterodimerization. Two conserved prolines (Pro(676) and Pro(683)), occupying consecutive b positions of the heptad, were not required for E1E2 heterodimerization; however, Pro(683) was critical for viral entry. Thus, disruption of the predicted alpha-helical structure by proline at position 683 is important for E2 function. The inability of mutants to mediate viral entry was not explained by a loss of receptor binding function, because all mutants were able to interact with a recombinant form of the CD81 large extracellular loop. Chimeras formed between the E1 and E2 ectodomains and the transmembrane domains of flavivirus prM and E glycoproteins, respectively, were able to heterodimerize, although with lower efficiency in comparison with wild type E1E2. The heptad repeat of E2 therefore requires the native transmembrane domain for full heterodimerization and viral entry function. Our data indicate that the membrane-proximal heptad repeat of E2 is functionally homologous to the stem of flavivirus E glycoproteins. We propose that E2 has mechanistic features in common with class II fusion proteins.