ABSTRACT
Analysis of the Yersinia pseudotuberculosis and Yersinia pestis genomes indicates that both species carry an identical copy of a gene that is predicted to encode a protein which shares 80% similarity to the Yersinia enterocolitica YplA, a secreted phospholipase that has been shown to contribute to virulence. In contrast to well tolerated production of the Y. enterocolitica YplA in Escherichia coli, Y. pseudotuberculosis YplA expression was found to be toxic; however, cell viability could be restored if the Y. pseudotuberculosis YplA was expressed in the presence of its accessory protein YplB. In vitro, Y. pseudotuberculosis YplB was shown to reduce the activity of its cognate phospholipase in a dose-dependent manner. To determine whether the Y. pseudotuberculosis and Y. enterocolitica YplAs were secreted and regulated in a similar manner, secretion and promoter activity assays were performed. Unlike the situation apparent in Y. enterocolitica, expression of the Y. pseudotuberculosis yplA gene did not appear to be controlled by the flagellar regulon, nor did the phospholipase appear to be efficiently exported through the flagellar apparatus. These results indicate that the Yersinia YplAs vary in many of their attributes despite their high degree of amino acid homology.
