CHARACTERIZATION OF A PERIPLASMIC PEPTIDYL-PROLYL CIS-TRANS ISOMERASEIN ERWINIA-CHRYSANTHEMI

The main determinant of the plant pathogen Erwinia chrysanthemi virule nce is the production of extracellular enzymes, mainly pectate lyases. Adjacent to a pectate lyase encoding locus, we identified the gene ro tA supposed to encode a folding catalyst. Overproduction of the protei n and assay of activity using a synthetic substrate, confirmed that ro tA encodes a periplasmic peptidyl-prolyl cis-trans isomerase. rotA dis ruption provokes no change in cell morphology, cell viability, growth rate or stability of the extracellular and periplasmic proteins. In ad dition, this mutation does not alter the activity of the pectate lyase s, their stability in the periplasm during the transitory step of secr etion or their recognition by the Out secretory system. rotA expressio n was followed using a rotA::uidA transcriptional fusion. Some environ mental conditions, such as temperature variations and nitrogen starvat ion, modulate rotA expression. In contrast to the E. coli rotA gene, t he E. chrysanthemi rotA possesses only one promoter and is not control led by the CRP global regulator.