Genetic analysis of the 9.5-kilobase virulence plasmid of Yersinia pestis.

The 9.5-kilobase plasmid of Yersinia pestis determines plasminogen activator, coagulase, pesticin, and pesticin immunity activities. We have mapped and cloned the loci encoding these activities and demonstrated that both plasminogen activator and coagulase were determined by the same gene, designated pla. The primary translation product of this gene (38 kilodaltons [kDa]) was processed in two sequential steps to produce peptides of 37 and 35 kDa. The first step in this processing occurred rapidly and probably cotranslationally and was blocked when protein export was inhibited. The second step was much slower and resulted in the presence of both the 37- and 35-kDa species in significant quantities. We also showed that the plasmid had a polA-dependent replicon and identified the region that contained its origin of replication and incompatibility functions.