Adhesive properties conferred by the plasminogen activator of Yersinia pestis

A genomic library of Yersinia pestis EV76c created in a cosmid vector was screened for clones capable of binding type IV collagen. An unexpectedly high number of such clones was observed. One recombinant plasmid was selected for further study, and the locus controlling collagen binding was mapped by subcloning, transposon mutagenesis and exonuclease digestion. The outer-membrane protein profiles of transposon insertion mutants were correlated with phenotype to implicate a 36 kDa polypeptide in type IV collagen binding. Fine substructure restriction mapping and limited DNA sequence analysis showed the cloned locus to be identical to the locus (pla) for the plasminogen activator, previously characterized genetically and biochemically. The pla locus is resident on a 9.5 kb plasmid in wild-type Y. pestis strains. Curing of this plasmid resulted in negligible reduction in collagen-binding capacity, implying the existence of a chromosomally located determinant for collagen binding. The affinity of the plasminogen activator for collagen was relatively weak. When the cloned pla locus was introduced into E. coli, it conferred upon the cell the ability to bind to cells from a number of cell lines. Binding to glycolipids separated by thin-layer chromatography demonstrated that the receptor was a member of the globo-series of glycolipids. Since it has been reported that mutation of pla dramatically reduces virulence, we propose that this hitherto undescribed function of the gene product could contribute to the biological activities necessary for full virulence.