Flynn D C, Meyer W J, Mackenzie J M, Johnston R E
Department of Microbiology and Immunology, University of North Carolina, Chapel Hill 27599-7290.
J Virol. 1990 Aug;64(8):3643-53. doi: 10.1128/JVI.64.8.3643-3653.1990.
A conformational change in the structure of Sindbis (SB) virus was detected after virion attachment to baby hamster kidney cells but before internalization. The alteration was manifested as increased virion binding of certain glycoprotein E1 and E2 monoclonal antibodies (MAbs) that recognized transitional epitopes. These epitopes were inaccessible to MAb on native virions but became accessible to their cognate MAbs in the early stages of infection. Transit of virions through a low-pH compartment apparently was not required for the conformational change. Exposure of transitional epitopes was unaffected by treatment of BHK cells with NH4Cl and occurred normally in Chinese hamster ovary cells temperature sensitive for endosomal acidification. However, the rearrangement was correlated with both the time course and temperature dependence of SB virus penetration, and the rearrangement occurred earlier with an SB virus mutant having an accelerated penetration phenotype. In addition, MAb to a transitional epitope, a probe specific for rearranged particles, retarded penetration of infectious virions. These results suggested that the SB virus E1/E2 glycoprotein spike undergoes a structural rearrangement as a consequence of virion interaction with the cell surface and that this altered virion form may be an important early intermediate in an entry pathway leading to productive infection.
在辛德毕斯（SB）病毒粒子附着于幼仓鼠肾细胞后但内化之前，检测到其结构发生了构象变化。这种改变表现为某些识别过渡性表位的糖蛋白E1和E2单克隆抗体（MAb）与病毒粒子的结合增加。这些表位在天然病毒粒子上不能被MAb识别，但在感染早期可被其同源MAb识别。病毒粒子通过低pH区室的转运显然不是构象变化所必需的。过渡性表位的暴露不受用氯化铵处理BHK细胞的影响，并且在对内体酸化温度敏感的中国仓鼠卵巢细胞中正常发生。然而，这种重排与SB病毒穿透的时间进程和温度依赖性相关，并且对于具有加速穿透表型的SB病毒突变体，重排发生得更早。此外，针对过渡性表位的MAb（一种针对重排颗粒的特异性探针）会延迟感染性病毒粒子的穿透。这些结果表明，SB病毒E1/E2糖蛋白刺突由于病毒粒子与细胞表面的相互作用而发生结构重排，并且这种改变的病毒粒子形式可能是导致有效感染的进入途径中的重要早期中间体。
