Signal peptide cleavage in the E . coli membrane

Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, B.C. Canada V6T 1Z3 Abstract Our laboratory uses x-ray crystallography and other structural biology techniques in the analysis of bacterial membrane proteins and membrane protein complexes. We are particularly interested in bacterial protein secretion machinery, including the Sec-dependent translocation apparatus which is essential to the viability of all bacteria, as well as the type III secretion apparatus which is specific to bacterial pathogens. The latter is a fascinating system which apparently acts as a “molecular syringe” to inject virulence proteins directly from the pathogenic bacteria into the host cell. In this paper we focus on one step of the Sec-dependent translocation of proteins, the essential cleavage of the signal peptide from membrane embedded pre-proteins during the translocation cycle.