Calcium-responsive expression of plasmid-mediated outer membrane proteins from Yersinia enterocolitica grown on solid media.

Abstract

In vitro synthesis of proteins directed by Yersinia enterocolitica virulence plasmid DNA was studied using a cell-free Escherichia 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-bearing Y. 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 in Y. 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 microM) 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.