Subdomain Folding and Biological Activity of the Core Structure from Human Immunodeficiency Virus Type 1 gp41: Implications for Viral Membrane Fusion

The envelope glycoprotein of human immunodeficiency virus type 1 (HIV-1) consists of two subunits, gp120 and gp41. The extraviral portion (ectodomain) of gp41 contains an α-helical domain that likely represents the core of the fusion-active conformation of the molecule. Here we report the identification and characterization of a minimal, autonomous folding subdomain that retains key determinants in specifying the overall fold of the gp41 ectodomain core. This subdomain, designated N34(L6)C28, is formed by covalent attachment of peptides N-34 and C-28 by a short flexible linker in place of the normal disulfide-bonded loop sequence. N34(L6)C28 forms a highly thermostable, α-helical trimer. Point mutations within the envelope protein complex that abolish membrane fusion and HIV-1 infectivity also impede the formation of the N34(L6)C28 core. Moreover, N34(L6)C28 is capable of inhibiting HIV-1 envelope-mediated membrane fusion. Taken together, these results indicate that the N34(L6)C28 core plays a direct role in the membrane fusion step of HIV-1 infection and thus provides a molecular target for the development of antiviral pharmaceutical agents.

人类免疫缺陷病毒1型（HIV-1）的包膜糖蛋白由gp120与gp41两个亚基组成。gp41的病毒外区域（胞外域）包含一个α螺旋结构域，该结构域大概率是该分子融合活性构象的核心区域。本研究报道了一个最小化自主折叠亚结构域的鉴定与表征工作，该亚结构域保留了决定gp41胞外域核心整体折叠模式的关键决定簇。该亚结构域被命名为N34(L6)C28，其通过一段短柔性连接肽将N-34肽与C-28肽共价连接而成，替代了原本的二硫键连接环序列。N34(L6)C28可形成高度热稳定的α螺旋三聚体。包膜蛋白复合物中能够阻断膜融合与HIV-1感染性的点突变，同样会阻碍N34(L6)C28核心的形成。此外，N34(L6)C28能够抑制HIV-1包膜介导的膜融合过程。综上，上述结果表明N34(L6)C28核心在HIV-1感染的膜融合步骤中发挥直接作用，因此可为抗病毒药物的研发提供分子靶点。