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

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。逆转录病毒感染的一个重要步骤是一个被称为“成熟”的过程，在这个过程中，病毒CA蛋白形成一个封闭的衣壳，保护和组织RNA基因组。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）。尽管衣壳形态存在差异，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六聚体CA晶格上，并通过加入五聚体倾角闭合（Ganser等，1999；Li等，2000）。六聚晶格内赤纬的相对分布决定了衣壳的形状。两个互补的模型系统已经被不同的小组用来检验这一假设。首先，体外组装的低分辨率生化和EM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，CA n端结构域（NTD）形成六聚体，c端结构域（CTD）形成连接相邻六聚体的二聚体连接体（Li等人，2000；Mayo等人，2002；Wilk等人，2001）。其次，截断蛋白的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等人，2005；Jin等人，1999；Mortuza等人，2004；Worthylake等人，1999）。此外，生化研究表明，NTD-CTD相互作用的存在对于衣壳的形成至关重要（Ganser-Pornillos等，2004；Lanman等，2003）。因此，需要一个全长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.