The Ohio State University, Department of Chemistry, Columbus, Ohio 43210.
Annu Rev Biochem. 2011;80:161-87. doi: 10.1146/annurev-biochem-060409-092524.
Numerous membrane proteins form multisubunit protein complexes, which contain both integral and peripheral subunits, in addition to prosthetic groups. Bacterial membrane proteins are inserted into the inner membrane by the Sec translocase and YidC insertase. Their folding can be facilitated by YidC and the phospholipid phosphatidylethanolamine (PE). Glycine zippers and other motifs promote transmembrane-transmembrane (TM-TM) helix interactions that may lead to the formation of α-helical bundles of membrane proteins. During or after membrane insertion, the subunits of oligomeric membrane proteins must find each other to build the homo-oligomeric and the hetero-oligomeric membrane complexes. Although chaperones may function as assembly factors in the formation of the oligomer, many protein oligomers appear to fold and oligomerize spontaneously. Current studies show that most subunits of hetero-oligomers follow a sequential and ordered pathway to form the membrane protein complex. If the inserted protein is misfolded or the membrane protein is misassembled, quality control mechanisms exist that can degrade the proteins.
许多膜蛋白形成多亚基蛋白复合物，除了辅因子外，还包含整合和外周亚基。细菌膜蛋白通过 Sec 易位子和 YidC 插入酶插入内膜。YidC 和磷脂磷脂酰乙醇胺 (PE) 可以促进它们的折叠。甘氨酸拉链和其他模体促进跨膜-跨膜 (TM-TM) 螺旋相互作用，可能导致膜蛋白的 α-螺旋束的形成。在膜插入期间或之后，寡聚膜蛋白的亚基必须相互找到彼此，以构建同聚寡聚体和异聚寡聚体膜复合物。虽然伴侣蛋白可能在寡聚体的形成中作为组装因子发挥作用，但许多蛋白寡聚体似乎可以自发折叠和寡聚化。目前的研究表明，大多数异聚寡聚体的亚基遵循顺序和有序的途径形成膜蛋白复合物。如果插入的蛋白质错误折叠或膜蛋白组装错误，则存在质量控制机制可以降解这些蛋白质。
