Cryo-electron microscopy of tubular arrays of HIV-1 Gag resolves structures essential for immature virus assembly
Cryo-electron microscopy of tubular arrays of HIV-1 Gag resolves structures essential for immature virus assembly
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DOI：
10.1073/pnas.1401455111
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发表时间：
2014-06-03
影响因子：
11.1
通讯作者：
Briggs, John A. G.
中科院分区：
文献类型：
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作者：
Bharat, Tanmay A. M.;Menendez, Luis R. Castillo;Briggs, John A. G.
HIV-1的组装是通过主要结构多聚蛋白Gag寡聚化为感染细胞质膜上的六聚体蛋白晶格来介导的。这导致后代未成熟病毒颗粒的出芽和释放。随后Gag的蛋白水解裂解触发颗粒重排以形成成熟的感染性病毒体。获得未成熟病毒颗粒内Gag组装晶格的结构模型对于理解介导HIV-1颗粒在感染细胞中组装的相互作用以及描述随后被病毒蛋白酶切割的底物是必要的。先前已经报道了由相关逆转录病毒Mason-Pfizer猴病毒（M-PMV）的GAG衍生蛋白组装的未成熟病毒样管状阵列的8埃分辨率结构，并且基于与该结构的同源性已经产生了HIV-1衣壳（CA）结构域的排列模型。在这里，我们组装了HIV-1 Gag衍生蛋白的管状阵列，其中C末端CA结构域呈不成熟样排列，并通过使用混合冷冻EM和断层扫描分析解决了它们的结构。该结构揭示了CA的C-末端结构域在一个不成熟的HIV-1 Gag晶格内的排列，并提供了据我们所知，CA下游区域的第一个高分辨率视图，这对组装至关重要，并且与M-PMV中的相应区域显著不同。我们的研究结果揭示了一个空心柱的密度为这一地区的HIV-1是兼容的存在下，在这个位置的六螺旋束。
The assembly of HIV-1 is mediated by oligomerization of the major structural polyprotein, Gag, into a hexameric protein lattice at the plasma membrane of the infected cell. This leads to budding and release of progeny immature virus particles. Subsequent proteolytic cleavage of Gag triggers rearrangement of the particles to form mature infectious virions. Obtaining a structural model of the assembled lattice of Gag within immature virus particles is necessary to understand the interactions that mediate assembly of HIV-1 particles in the infected cell, and to describe the substrate that is subsequently cleaved by the viral protease. An 8-angstrom resolution structure of an immature virus-like tubular array assembled from a Gag-derived protein of the related retrovirus Mason-Pfizer monkey virus (M-PMV) has previously been reported, and a model for the arrangement of the HIV-1 capsid (CA) domains has been generated based on homology to this structure. Here we have assembled tubular arrays of a HIV-1 Gag-derived protein with an immature-like arrangement of the C-terminal CA domains and have solved their structure by using hybrid cryo-EM and tomography analysis. The structure reveals the arrangement of the C-terminal domain of CA within an immature-like HIV-1 Gag lattice, and provides, to our knowledge, the first high-resolution view of the region immediately downstream of CA, which is essential for assembly, and is significantly different from the respective region in M-PMV. Our results reveal a hollow column of density for this region in HIV-1 that is compatible with the presence of a six-helix bundle at this position.