Altered localization of HrpZ in Pseudomonas syringae pv. syringae hrp mutants suggests that different components of the type III secretion pathway control protein translocation across the inner and outer membranes of gram-negative bacteria

The modified distribution of the HrpZ hairpin protein in Pseudomonas syringae pv. syringae 61 hrp mutants was found to allow assignment of these four operons to two experimentally identifiable stages in type III protein secretion. The hrpJ and hrpU operons encode an alternative to the Sec system for translocation across the inner membrane, while the hrpC operon is needed for translocation across the outer membrane.