Calcium-responsive expression of plasmid-mediated outer membrane proteins fromYersinia enterocolitica grown on solid media

Summary

In vitro synthesis of proteins directed byYersinia enterocolitica virulence plasmid DNA was studied using a cell-freeEscherichia coli coupled transcription-translation system. Out of a total of twenty-four polypeptides synthesized in vitro, ten were identified (based on virtually identical molecular masses) as outer membrane proteins synthesized in vivo when virulent plasmid-bearingY. enterocolitica cells were grown on four different solid media. Two high molecular weight outer membrane proteins synthesized in vivo by plasmid-bearing cells were not detected in the in vitro protein synthesizing system. Different plasmid-mediated outer membrane proteins were expressed in vivo inY. enterocolitica grown on different media.Y. enterocolitica grown on media with high calcium concentration (1·4–1·5 mM) expressed twice the number of lower molecular weight outer membrane proteins than the organism grown on low calcium (238–311 μM) media. This is the first report that a single serotype has been shown to synthesize all the reported virulence plasmid-encoded outer membrane proteins including three new polypeptides. The constituents in the medium as well as the level of calcium appeared to have a regulatory role in plasmid gene expression for lower molecular weight outer membrane proteins.