Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK.
Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
Commun Biol. 2021 Apr 16;4(1):481. doi: 10.1038/s42003-021-01999-1.
Gag is the HIV structural precursor protein which is cleaved by viral protease to produce mature infectious viruses. Gag is a polyprotein composed of MA (matrix), CA (capsid), SP1, NC (nucleocapsid), SP2 and p6 domains. SP1, together with the last eight residues of CA, have been hypothesized to form a six-helix bundle responsible for the higher-order multimerization of Gag necessary for HIV particle assembly. However, the structure of the complete six-helix bundle has been elusive. Here, we determined the structures of both Gag in vitro assemblies and Gag viral-like particles (VLPs) to 4.2 Å and 4.5 Å resolutions using cryo-electron tomography and subtomogram averaging by emClarity. A single amino acid mutation (T8I) in SP1 stabilizes the six-helix bundle, allowing to discern the entire CA-SP1 helix connecting to the NC domain. These structures provide a blueprint for future development of small molecule inhibitors that can lock SP1 in a stable helical conformation, interfere with virus maturation, and thus block HIV-1 infection.
Gag 是 HIV 的结构前体蛋白，可被病毒蛋白酶切割产生成熟的感染性病毒。Gag 是一种由 MA（基质）、CA（衣壳）、SP1、NC（核衣壳）、SP2 和 p6 结构域组成的多蛋白。SP1 与 CA 的最后 8 个残基一起，被假设形成一个六螺旋束，负责 Gag 的高级多聚化，这是 HIV 颗粒组装所必需的。然而，完整六螺旋束的结构仍然难以捉摸。在这里，我们使用 cryo-electron tomography 和 emClarity 的子断层平均化技术，将体外组装的 Gag 和 Gag 病毒样颗粒（VLPs）的结构分别解析至 4.2Å 和 4.5Å 的分辨率。SP1 中的单个氨基酸突变（T8I）稳定了六螺旋束，从而能够辨别与 NC 结构域相连的整个 CA-SP1 螺旋。这些结构为未来开发小分子抑制剂提供了蓝图，这些抑制剂可以将 SP1 锁定在稳定的螺旋构象中，干扰病毒成熟，从而阻断 HIV-1 感染。
