Cytoplasmic and membrane proteins of yersiniae cultivated under conditions simulating mammalian intracellular environment.

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Abstract
A procedure is described for fractionating Yersinia grown in small cultures into inner and outer membranes and soluble cytoplasmic proteins. The procedure was applied to the three recognized species of the genus grown under conditions simulating mammalian intracellular fluid with respect to Ca2+ and Mg2+. These conditions are known to elicit the production of the plague virulence antigen V. Isolates capable of making this antigen were compared with virulence-antigen-negative derivatives by two-dimensional electrophoresis. The V antigen was localized to the soluble protein fraction as a peptide that comigrates with the major component of a specific immunoprecipitate. This peptide had an apparent molecular weight of 38,000 and was not found in either apparent molecular weight of 38,000 and was not found in either membrane fraction. The comparison of virulence antigen-producers and nonproducers of Y. pseudotuberculosis and Y. enterocolitica revealed large qualitative and quantitative differences in outer membrane protein patterns, whereas the same comparison for Y. pestis showed only minor differences. The complexity of changes in the various protein fractions corroborate data in the literature indicating that extensive physiological changes occur in virulent organisms cultivated under simulated intracellular conditions.