Zuber G, McDermott J, Karanjia S, Zhao W, Schmid M F, Barklis E
Laboratoire de Chimie Genetique, Faculté de Pharmacie, University of Strasbourg, Strasbourg, France.
J Virol. 2000 Aug;74(16):7431-41. doi: 10.1128/jvi.74.16.7431-7441.2000.
Retrovirus Gag precursor (PrGag) proteins direct the assembly of roughly spherical immature virus particles, while after proteolytic processing events, the Gag capsid (CA) and nucleocapsid (NC) domains condense on viral RNAs to form mature retrovirus core structures. To investigate the process of retroviral morphogenesis, we examined the properties of histidine-tagged (His-tagged) Moloney murine leukemia (M-MuLV) capsid plus nucleocapsid (CANC) (His-MoCANC) proteins in vitro. The His-MoCANC proteins bound RNA, possessed nucleic acid-annealing activities, and assembled into strand, circle (or sphere), and tube forms in the presence of RNA. Image analysis of electron micrographs revealed that tubes were formed by cage-like lattices of CANC proteins surrounding at least two different types of protein-free cage holes. By virtue of a His tag association with nickel-chelating lipids, His-MoCANC proteins also assembled into planar sheets on lipid monolayers, mimicking the membrane-associated immature PrGag protein forms. Membrane-bound His-MoCANC proteins organized into two-dimensional (2D) cage-like lattices that were closely related to the tube forms, and in the presence of both nickel-chelating lipids and RNAs, 2D lattice forms appeared similar to lattices assembled in the absence of RNA. Our observations are consistent with a M-MuLV morphogenesis model in which proteolytic processing of membrane-bound Gag proteins permits CA and NC domains to rearrange from an immature spherical structure to a condensed mature form while maintaining local protein-protein contacts.
逆转录病毒Gag前体（PrGag）蛋白指导大致呈球形的未成熟病毒颗粒的组装，而在蛋白水解加工事件之后，Gag衣壳（CA）和核衣壳（NC）结构域在病毒RNA上凝聚形成成熟的逆转录病毒核心结构。为了研究逆转录病毒形态发生的过程，我们在体外检测了组氨酸标签化（His标签化）的莫洛尼氏鼠白血病病毒（M-MuLV）衣壳加核衣壳（CANC）（His-MoCANC）蛋白的特性。His-MoCANC蛋白能结合RNA，具有核酸退火活性，并在有RNA存在的情况下组装成链状、环状（或球状）和管状结构。电子显微镜照片的图像分析显示，管状结构是由CANC蛋白的笼状晶格围绕至少两种不同类型的无蛋白笼孔形成的。由于His标签与镍螯合脂质相关联，His-MoCANC蛋白也能在脂质单层上组装成平面片层，模拟与膜相关的未成熟PrGag蛋白形式。膜结合的His-MoCANC蛋白组织成二维（2D）笼状晶格，与管状结构密切相关，并且在同时存在镍螯合脂质和RNA的情况下，2D晶格形式与在无RNA情况下组装的晶格相似。我们的观察结果与M-MuLV形态发生模型一致，在该模型中，膜结合Gag蛋白的蛋白水解加工允许CA和NC结构域从未成熟的球形结构重排为凝聚的成熟形式，同时保持局部蛋白质-蛋白质接触。
