TAILIEUCHUNG - Báo cáo khoa học: Protein transport across the endoplasmic reticulum membrane

A decisive step in the biosynthesis of many eukaryotic proteins is their par-tial or complete translocation across the endoplasmic reticulum membrane. A similar process occurs in prokaryotes, except that proteins are trans-ported across or are integrated into the plasma membrane. | IFEBS Journal THE SIR HANS KREBS LECTURE Protein transport across the endoplasmic reticulum membrane Delivered on 8 July 2007 at the 32nd FEBS Congress in Vienna Austria Tom A. Rapoport Howard Hughes Medical institute and Department of Cell Biology Harvard Medical School Boston MA USA Keywords endoplasmic reticulum lipid membrane integration protein-conducting channel protein translocation ribosome Sec complex Sec61 SecA SecY Correspondence T. A. Rapoport Howard Hughes Medical Institute and Department of Cell Biology Harvard Medical School 240 Longwood Avenue Boston MA 02115 USA Fax 1 617 432 1190 Tel 1 617 432 0676 E-mail tom_rapoport@ Received 21 May 2008 accepted 18 June 2008 doi A decisive step in the biosynthesis of many eukaryotic proteins is their partial or complete translocation across the endoplasmic reticulum membrane. A similar process occurs in prokaryotes except that proteins are transported across or are integrated into the plasma membrane. In both cases translocation occurs through a protein-conducting channel that is formed from a conserved heterotrimeric membrane protein complex the Sec61 or SecY complex. Structural and biochemical data suggest mechanisms that enable the channel to function with different partners to open across the membrane and to release laterally hydrophobic segments of membrane proteins into lipid. Introduction Protein translocation across the eukaryotic endoplasmic reticulum ER membrane is a decisive step in the biosynthesis of many proteins 1 . These include soluble proteins such as those ultimately secreted from the cell or localized to the ER lumen and membrane proteins such as those in the plasma membrane or in other organelles of the secretory pathway. Soluble proteins cross the membrane completely and usually have cleavable N-terminal signal sequences whose major feature is a segment of approximately seven to 12 hydrophobic amino acids. Integral membrane proteins have one

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