THE HIGH-RESOLUTION STRUCTURE OF M-MLV CA ASSEMBLED ON A LIPID MONOLAYER: HIV

该子项目是利用 NIH/NCRR 资助的中心拨款提供的资源的众多研究子项目之一。子项目和研究者 (PI) 可能已从另一个 NIH 来源获得主要资金，因此可以在其他 CRISP 条目中出现。列出的机构是中心的机构，不一定是研究者的机构。逆转录病毒感染性的一个重要步骤是一个称为“成熟”的过程，其中病毒 CA 蛋白形成封闭的衣壳，起到保护和组织 RNA 基因组的作用。成熟的逆转录病毒衣壳可以是圆锥形（HIV）、球形（M-MLV）或圆柱形（MPMV）（Vogt，1997）。尽管衣壳形态存在这种变化，但所有逆转录病毒CA蛋白的三级结构都是高度保守的，这表明不同的衣壳形状源于共同的设计原则。 我们之前提出，所有逆转录病毒衣壳都是建立在 CA 的六聚体晶格上，并通过合并五聚体偏角来封闭（Ganser 等，1999；Li 等，2000）。六聚晶格内磁偏角的相对分布决定了衣壳的形状。 不同的小组使用了两个互补的模型系统来检验这一假设。首先，体外组装的低分辨率生化和电镜研究表明，全长 HIV-1 和逆转录病毒 CA 蛋白确实形成六聚体晶格，其中 CA N 端结构域 (NTD) 形成六聚体，而 C 端结构域 (CTD) 形成连接相邻六聚体的二聚体接头 (Li 等人，2000；Mayo 等人，2002；Wilk 等人，2001)。其次，截短蛋白的 X 射线晶体学研究揭示了 M-MLV 六聚结构域的高分辨率模型，以及 CA 二聚结构域的几种可能模型（Ivanov 等，2005；Jin 等，1999；Mortuza 等，2004；Worthylake 等，1999）。此外，生化研究表明 NTD-CTD 相互作用的存在对于衣壳形成至关重要（Ganser-Pornillos 等，2004；Lanman 等，2003）。因此，需要全长 CA 组件的高分辨率结构模型来明确定义 NTD 六聚体使用的蛋白质-蛋白质界面，确定正确的 CTD 二聚体，并表征未定义的 NTD-CTD 界面。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. An essential step in retroviral infectivity is a process called ¿maturation¿, wherein the viral CA protein forms a closed capsid that acts to protect and organize the RNA genome. Mature retroviral capsids can be conical (HIV), spherical (M-MLV), or cylindrical (MPMV)(Vogt, 1997). Despite this variation in capsid morphology, the tertiary structure of all retroviral CA proteins is highly conserved, indicating that the different capsid shapes arise from common design principles. We have previously proposed that all retroviral capsids are built on hexameric lattices of CA and closed by incorporating pentameric declinations(Ganser et al., 1999; Li et al., 2000). The relative distribution of the declinations within the hexameric lattice defines the shape of the capsid. Two complementary model systems have been used by various groups to test this hypothesis. First, low-resolution biochemical and EM studies of in vitro assemblies have shown that full-length HIV-1 and retroviral CA proteins do form hexameric lattices, with the CA N-terminal domain (NTD) forming the hexamers, and the C-terminal domain (CTD) forming dimeric linkers that connect neighboring hexamers (Li et al., 2000; Mayo et al., 2002; Wilk et al., 2001). Second, x-ray crystallographic studies of truncated proteins have revealed a high-resolution model for the M-MLV hexameric domain, and several possible models for the CA dimerization domain(Ivanov et al., 2005; Jin et al., 1999; Mortuza et al., 2004; Worthylake et al., 1999). In addition, biochemical studies suggest the existence of NTD-CTD interactions essential for capsid formation(Ganser-Pornillos et al., 2004; Lanman et al., 2003). Therefore, a high-resolution structural model for full-length CA assemblies is required to unambiguously define protein-protein interfaces used by the NTD hexamer, determine the correct CTD dimer, and characterize the undefined NTD-CTD interface.