E. coli preprotein translocase: A 6 stroke engine with 2 fuels and 2 piston rods

Abstract

The elucidation of the pathway for preprotein transit across the plasma membrane of E. coli is a fine example of the synergy between genetic, biochemical, and physiological approaches to study a common problem. Early physiological studies of secretion by Ito and by Randall established important boundary parameters; secretion requires metabolic energy and is not coupled to ongoing polypeptide chain growth. Genetic efforts in the labs of Beckwith and Silhavy were focused on obtaining prl supressor mutants with enhanced capacities to export proteins with mutant leader sequences and sec mutants which were temperature sensitive in the export process itself. In our lab, the biochemical studies of this era focused on the sec-independent Ml3 procoat protein and on the isolation of leader peptidase.