Rapoport Tom A
Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA.
Nature. 2007 Nov 29;450(7170):663-9. doi: 10.1038/nature06384.
A decisive step in the biosynthesis of many proteins is their partial or complete translocation across the eukaryotic endoplasmic reticulum membrane or the prokaryotic plasma membrane. Most of these proteins are translocated through a protein-conducting channel that is formed by a conserved, heterotrimeric membrane-protein complex, the Sec61 or SecY complex. Depending on channel binding partners, polypeptides are moved by different mechanisms: the polypeptide chain is transferred directly into the channel by the translating ribosome, a ratcheting mechanism is used by the endoplasmic reticulum chaperone BiP, and a pushing mechanism is used by the bacterial ATPase SecA. Structural, genetic and biochemical data show how the channel opens across the membrane, releases hydrophobic segments of membrane proteins laterally into lipid, and maintains the membrane barrier for small molecules.
许多蛋白质生物合成过程中的一个决定性步骤是它们部分或完全跨真核生物内质网膜或原核生物质膜转运。这些蛋白质大多通过一个由保守的异源三聚体膜蛋白复合物Sec61或SecY复合物形成的蛋白质传导通道进行转运。根据通道结合伴侣的不同，多肽通过不同的机制移动：多肽链由正在翻译的核糖体直接转移到通道中，内质网伴侣BiP采用棘轮机制，细菌ATP酶SecA采用推动机制。结构、遗传和生化数据表明了通道如何跨膜打开，将膜蛋白的疏水片段侧向释放到脂质中，并维持对小分子的膜屏障。
