Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Annu Rev Biophys. 2012;41:21-40. doi: 10.1146/annurev-biophys-050511-102312. Epub 2011 Dec 16.
The Sec61 or SecY channel, a universally conserved protein-conducting channel, translocates proteins across and integrates proteins into the eukaryotic endoplasmic reticulum (ER) membrane and the prokaryotic plasma membrane. Depending on channel-binding partners, polypeptides are moved by different mechanisms. In cotranslational translocation, the ribosome feeds the polypeptide chain directly into the channel. In posttranslational translocation, a ratcheting mechanism is used by the ER-lumenal chaperone BiP in eukaryotes, and a pushing mechanism is utilized by the SecA ATPase in bacteria. In prokaryotes, posttranslational translocation is facilitated through the function of the SecD/F protein. Recent structural and biochemical data show how the channel opens during translocation, translocates soluble proteins, releases hydrophobic segments of membrane proteins into the lipid phase, and maintains the barrier for small molecules.
Sec61 或 SecY 通道是一种普遍保守的蛋白通道，它能将蛋白穿过并整合到真核内质网（ER）膜和原核质膜中。根据通道结合伙伴的不同，多肽通过不同的机制移动。在共翻译易位中，核糖体直接将多肽链送入通道。在后翻译易位中，内质网腔伴侣 BiP 在真核生物中使用棘轮机制，SecA ATP 酶在细菌中使用推动机制。在原核生物中，后翻译易位是通过 SecD/F 蛋白的功能来促进的。最近的结构和生化数据显示了通道在易位过程中如何打开，易位可溶性蛋白，将膜蛋白的疏水区段释放到脂质相中，并维持小分子的屏障。
