Lobigs M, Wahlberg J M, Garoff H
Department of Molecular Biology, Karolinska Institute, Huddinge, Sweden.
J Virol. 1990 Oct;64(10):5214-8. doi: 10.1128/JVI.64.10.5214-5218.1990.
We have recently shown, using cleavage-deficient mutants of the p62-E1 membrane protein complex of Semliki Forest virus that p62 cleavage to E2 is necessary for the activation of the fusion function of the complex at pH 5.8 (a pH optimal for virus fusion) (M. Lobigs and H. Garoff, J. Virol. 64:1233-1240, 1990). In this study, we show that the mutant precursor complexes can be induced to activate membrane fusion when treated with more acidic buffers (pH 5.0 and 4.5), which also appear to dissociate most of the p62-E1 complexes and change the conformation of the E1 subunit (the supposed fusion protein of Semliki Forest virus into a form which is resistant to trypsin digestion. These data suggest that p62 cleavage is not essential for membrane fusion per se but that the crucial event activating this process seems to be the apparent dissociation of the heterodimer, which in turn is facilitated by the spike precursor cleavage.
我们最近利用塞姆利基森林病毒的p62-E1膜蛋白复合物的切割缺陷型突变体表明，在pH 5.8（病毒融合的最佳pH值）时，p62切割成E2对于激活该复合物的融合功能是必要的（M. 洛比格斯和H. 加罗夫，《病毒学杂志》64:1233 - 1240，1990年）。在本研究中，我们表明，当用更酸性的缓冲液（pH 5.0和4.5）处理时，突变体前体复合物可被诱导激活膜融合，这似乎也会使大多数p62-E1复合物解离，并改变E1亚基（塞姆利基森林病毒假定的融合蛋白）的构象，使其变成一种对胰蛋白酶消化具有抗性的形式。这些数据表明，p62切割本身对于膜融合并非必不可少，但激活这一过程的关键事件似乎是异二聚体的明显解离，而这反过来又因刺突前体的切割而得到促进。
