Biogenesis of Inner Membrane Proteins in Escherichia coli Joen Luirink, 1 Gunnar von Heijne, 2 Edith Houben, 1 and Jan-Willem de Gier 2 1 Department of Microbiology, Institute of Molecular Cell Biology, Vrije Universiteit, 1081 HV Amsterdam, The Netherlands; email: joen.luirink@falw.vu.nl 2 Department of Biochemistry and Biophysics, Stockholm University, 106 91 Stockholm, Sweden Annu. Rev. Microbiol. 2005. 59:329–55 The Annual Review of Microbiology is online at micro.annualreviews.org doi: 10.1146/ annurev.micro.59.030804.121246 Copyright c  2005 by Annual Reviews. All rights reserved 0066-4227/05/1013- 0329$20.00 Key Words membrane protein assembly, protein targeting, ribosome, YidC, SRP, Sec-translocon Abstract Gram-negative bacteria such as Escherichia coli are surrounded by two membranes, the inner membrane and the outer membrane. The bio- genesis of most inner membrane proteins (IMPs), typical α-helical proteins, appears to follow a partly conserved cotranslational path- way. Targeting involves a relatively simple signal recognition particle (SRP) and SRP-receptor. Insertion of most IMPs into the membrane occurs via the Sec-translocon, which is also used for the vectorial transport of secretory proteins. Similar to eukaryotic systems, little is known about the later stages of biogenesis of IMPs, the folding and assembly in the lipid bilayer. Recently, YidC has been identified as a factor that assists in the integration, folding, and assembly of IMPs both in association with the Sec-translocon and separately. This re- view deals mainly with recent structural and biochemical data from various experimental systems that offer new insight into the different stages of biogenesis of E. coli IMPs. 329 Annu. Rev. Microbiol. 2005.59:329-355. Downloaded from arjournals.annualreviews.org by Pohang University of Science and Technology (POSTECH) on 10/25/05. For personal use only.