Tucker S P, Srinivas R V, Compans R W
Department of Microbiology, University of Alabama, Birmingham 35294.
Virology. 1991 Dec;185(2):710-20. doi: 10.1016/0042-6822(91)90542-j.
The oligomeric structure of the Friend murine leukemia virus envelope glycoprotein has been investigated using crosslinking reagents and sucrose density gradient centrifugation. The results obtained provide evidence that both the precursor and the processed molecules are oligomeric and probably form tetramers. Pulse-chase analyses indicate that assembly occurs sequentially, within 30 min of protein synthesis and prior to cleavage of the precursor. Studies using chimeric envelope glycoproteins and deletion mutants indicate that the transmembrane and cytoplasmic domains are not essential for the formation of oligomers. Evidence is also presented that the SU subunit remains in an oligomeric form following disassociation from the TM subunit. Oligomeric envelope glycoprotein complexes linked by intermolecular disulfide bonds were also observed under certain conditions. Mink cell focus-forming virus envelope glycoprotein constructs lacking the transmembrane domain or both the transmembrane and the cytoplasmic domains formed intermolecular disulfide bonds more readily than the full-length molecule, suggesting that these regions are likely to make a contribution to the conformation of the glycoprotein. These data indicate that there are several points of interaction between retrovirus envelope glycoprotein monomers which contribute to assembly of the oligomer and that contacts within the ectodomain appear to be of critical importance.
利用交联试剂和蔗糖密度梯度离心法对弗瑞德小鼠白血病病毒包膜糖蛋白的寡聚结构进行了研究。所得结果表明，前体分子和加工后的分子均为寡聚体，可能形成四聚体。脉冲追踪分析表明，组装在蛋白质合成的30分钟内且在前体裂解之前依次发生。使用嵌合包膜糖蛋白和缺失突变体的研究表明，跨膜结构域和胞质结构域对于寡聚体的形成并非必不可少。还有证据表明，SU亚基与TM亚基解离后仍保持寡聚形式。在某些条件下还观察到通过分子间二硫键连接的寡聚包膜糖蛋白复合物。缺乏跨膜结构域或同时缺乏跨膜和胞质结构域的貂细胞集落形成病毒包膜糖蛋白构建体比全长分子更容易形成分子间二硫键，这表明这些区域可能对糖蛋白的构象有贡献。这些数据表明，逆转录病毒包膜糖蛋白单体之间存在多个相互作用点，这些点有助于寡聚体的组装，并且胞外域内的接触似乎至关重要。
