Kanesashi Shin-Nosuke, Ishizu Ken-Ichiro, Kawano Masa-Aki, Han Song-Iee, Tomita Satoru, Watanabe Hajime, Kataoka Kohsuke, Handa Hiroshi
Faculty of Bioscience and Biotechnology and Frontier Collaborative Research Center, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
Radioisotope Research Center, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
J Gen Virol. 2003 Jul;84(Pt 7):1899-1905. doi: 10.1099/vir.0.19067-0.
The simian virus 40 (SV40) capsid is composed of 72 pentamers of VP1, the major protein of SV40. These pentamers are arranged in a T=7d icosahedral surface lattice, which is maintained by three types of appropriately arranged, non-equivalent interactions between the pentamers. However, it remains unclear how these interactions are achieved. In this study, the in vitro assembly of recombinant VP1 was analysed. Electron microscopy observations revealed that these recombinant VP1 proteins assembled into structurally polymorphic particles depending on environmental conditions. VP1 pentamers assembled efficiently into virus-like particles (VLPs) when high concentrations of ammonium sulfate were present. However, in the presence of 1 M NaCl and 2 mM CaCl(2) at neutral pH, VP1 pentamers formed not only VLPs but also produced tiny T=1 icosahedral particles and tubular structures. The exclusion of CaCl(2) resulted in the exclusive formation of tiny particles. In contrast, in the presence of 150 mM NaCl at pH 5, the VP1 pentamers produced only extraordinarily long tubular structures. VP1 is thus quite unique in that it can assemble into such diverse structures. These observations provide clues that will help elucidate the mechanisms underlying SV40 capsid formation.
猴病毒40（SV40）衣壳由72个VP1五聚体组成，VP1是SV40的主要蛋白。这些五聚体排列成T=7d二十面体表面晶格，该晶格由五聚体之间三种适当排列的、不等价的相互作用维持。然而，这些相互作用是如何实现的仍不清楚。在本研究中，分析了重组VP1的体外组装。电子显微镜观察表明，这些重组VP1蛋白根据环境条件组装成结构多态性颗粒。当存在高浓度硫酸铵时，VP1五聚体有效地组装成病毒样颗粒（VLP）。然而，在中性pH值下存在1 M NaCl和2 mM CaCl₂时，VP1五聚体不仅形成VLP，还产生微小的T=1二十面体颗粒和管状结构。去除CaCl₂导致仅形成微小颗粒。相反，在pH 5时存在150 mM NaCl的情况下，VP1五聚体仅产生非常长的管状结构。因此，VP1非常独特，因为它可以组装成如此多样的结构。这些观察结果提供了有助于阐明SV40衣壳形成潜在机制的线索。
