ASSEMBLY OF A CYTOPLASMIC MEMBRANE-PROTEIN IN ESCHERICHIA-COLI IS DEPENDENT ON THE SIGNAL RECOGNITION PARTICLE

Targeting of the cytoplasmic membrane protein leader peptidase (Lep) a nd a Lep mutant (Lep-inv) that inserts with an inverted topology compa red to the wild-type protein was studied in Escherichia coli strains t hat are conditional for the expression of either Ffh or 4.5S RNA, the two components of the E. coli SRP, Depletion of either component stron gly affected the insertion of both Lep and Lep-inv into the cytoplasmi c membrane, This indicates that SRP is required for the assembly of cy toplasmic membrane proteins in E. coli.