Regulation of the Escherichia coli secA gene by protein secretion defects: analysis of secA, secB, secD, and secY mutants.

SecA protein synthesis levels were elevated 10- to 20-fold when protein secretion was blocked in secA, secD, and secY mutants or in a malE-lacZ fusion-containing strain but not in a secB null mutant. An active secB gene product was not required to derepress secA, since SecA levels were elevated during protein export blocks in secB secY and secB malE-lacZ double mutants.