Dubuisson J, Rice C M
Unité d'Oncologie Moléculaire, Centre National de la Recherche Scientifique--URA-1160, Institut Pasteur de Lille, France.
J Virol. 1996 Feb;70(2):778-86. doi: 10.1128/JVI.70.2.778-786.1996.
The hepatitis C virus (HCV) glycoproteins (E1 and E2) are released from the polyprotein by signal peptidase-mediated cleavage and interact to form a heterodimer. Since properly folded subunits are usually required for specific recognition and stable oligomer formation, the rate of stable E1E2 complex formation, which is low, may be limited by the rate of HCV E1 and/or E2 folding. In this study, the folding of the HCV E1 and E2 glycoproteins was monitored by observing the kinetics of intramolecular disulfide bond formation. The association/dissociation of E1 and E2 with calnexin was also examined, since this molecular chaperone appears to play a major role in quality control via retention of incompletely folded or misfolded proteins in the endoplasmic reticulum. Our results indicate that the disulfide-dependent folding of E2 occurs rapidly and appears to be complete upon cleavage of the precursor E2-NS2. In contrast, folding of E1 is slow (> 1 h), suggesting that this step may be rate limiting for E1E2 oligomerization. Both HCV glycoproteins associated rapidly with calnexin, but dissociation was slow, consistent with the slow folding and assembly of E1E2 glycoprotein complexes. These results suggest a role for prolonged association with calnexin in the folding and assembly of HCV glycoprotein heterodimer complexes.
丙型肝炎病毒（HCV）糖蛋白（E1和E2）通过信号肽酶介导的切割从多蛋白中释放出来，并相互作用形成异二聚体。由于特定识别和稳定寡聚体形成通常需要正确折叠的亚基，稳定的E1E2复合物形成速率较低，可能受HCV E1和/或E2折叠速率的限制。在本研究中，通过观察分子内二硫键形成的动力学来监测HCV E1和E2糖蛋白的折叠。还检测了E1和E2与钙连蛋白的结合/解离情况，因为这种分子伴侣似乎通过在内质网中保留未完全折叠或错误折叠的蛋白质在质量控制中发挥主要作用。我们的结果表明，E2的二硫键依赖性折叠迅速发生，并且在前体E2-NS2切割后似乎完成。相比之下，E1的折叠较慢（>1小时），表明该步骤可能是E1E2寡聚化的限速步骤。两种HCV糖蛋白都与钙连蛋白迅速结合，但解离缓慢，这与E1E2糖蛋白复合物缓慢的折叠和组装一致。这些结果表明，与钙连蛋白的长时间结合在HCV糖蛋白异二聚体复合物的折叠和组装中起作用。
