Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA.
Proc Natl Acad Sci U S A. 2010 Jun 29;107(26):11769-74. doi: 10.1073/pnas.1001760107. Epub 2010 Jun 14.
Rift Valley fever virus (RVFV) is a negative-sense RNA virus (genus Phlebovirus, family Bunyaviridae) that infects livestock and humans and is endemic to sub-Saharan Africa. Like all negative-sense viruses, the segmented RNA genome of RVFV is encapsidated by a nucleocapsid protein (N). The 1.93-A crystal structure of RVFV N and electron micrographs of ribonucleoprotein (RNP) reveal an encapsidated genome of substantially different organization than in other negative-sense RNA virus families. The RNP polymer, viewed in electron micrographs of both virus RNP and RNP reconstituted from purified N with a defined RNA, has an extended structure without helical symmetry. N-RNA species of approximately 100-kDa apparent molecular weight and heterogeneous composition were obtained by exhaustive ribonuclease treatment of virus RNP, by recombinant expression of N, and by reconstitution from purified N and an RNA oligomer. RNA-free N, obtained by denaturation and refolding, has a novel all-helical fold that is compact and well ordered at both the N and C termini. Unlike N of other negative-sense RNA viruses, RVFV N has no positively charged surface cleft for RNA binding and no protruding termini or loops to stabilize a defined N-RNA oligomer or RNP helix. A potential protein interaction site was identified in a conserved hydrophobic pocket. The nonhelical appearance of phlebovirus RNP, the heterogeneous approximately 100-kDa N-RNA multimer, and the N fold differ substantially from the RNP and N of other negative-sense RNA virus families and provide valuable insights into the structure of the encapsidated phlebovirus genome.
裂谷热病毒（RVFV）是一种负义 RNA 病毒（属 Phlebovirus，布尼亚病毒科），感染牲畜和人类，并且是撒哈拉以南非洲的地方病。与所有负义病毒一样，RVFV 的分段 RNA 基因组被核衣壳蛋白（N）包裹。RVFV N 的 1.93-A 晶体结构和核糖核蛋白（RNP）的电子显微镜照片显示，包裹的基因组的组织与其他负义 RNA 病毒家族的完全不同。在病毒 RNP 和用定义的 RNA 从纯化的 N 重新构成的 RNP 的电子显微镜照片中观察到的 RNP 聚合物具有没有螺旋对称的延伸结构。通过对病毒 RNP 进行彻底的核糖核酸酶处理、通过 N 的重组表达以及通过从纯化的 N 和 RNA 寡聚物重新构成，获得了大约 100kDa 表观分子量和异质组成的 N-RNA 物质。通过变性和复性获得的无 RNA N，具有新颖的全螺旋折叠，在 N 和 C 末端均紧凑且有序。与其他负义 RNA 病毒的 N 不同，RVFV N 没有用于 RNA 结合的带正电荷的表面裂缝，也没有突出的末端或环来稳定定义的 N-RNA 寡聚物或 RNP 螺旋。在保守的疏水性口袋中鉴定出一个潜在的蛋白质相互作用位点。黄病毒 RNP 的无螺旋外观、大约 100kDa 的异质 N-RNA 多聚体以及 N 折叠与其他负义 RNA 病毒家族的 RNP 和 N 有很大不同，为包裹的黄病毒基因组的结构提供了有价值的见解。
