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Plasminogen activator inhibitor 1 (PAI-1) is a serine protease inhibitor (serpin) and a key molecule that regulates fibrinolysis by inactivating human plasminogen activators. Here we show that two important human pathogens, the plague bacterium Yersinia pestis and the enteropathogen Salmonella enterica serovar Typhimurium, inactivate PAI-1 by cleaving the R346-M347 bait peptide bond in the reactive center loop. No cleavage of PAI-1 was detected with Yersinia pseudotuberculosis, an oral/fecal pathogen from which Y. pestis has evolved, or with Escherichia coli. The cleavage and inactivation of PAI-1 were mediated by the outer membrane proteases plasminogen activator Pla of Y. pestis and PgtE protease of S. enterica, which belong to the omptin family of transmembrane endopeptidases identified in Gram-negative bacteria. Cleavage of PAI-1 was also detected with the omptins Epo of Erwinia pyrifoliae and Kop of Klebsiella pneumoniae, which both belong to the same omptin subfamily as Pla and PgtE, whereas no cleavage of PAI-1 was detected with omptins of Shigella flexneri or E. coli or the Yersinia chromosomal omptins, which belong to other omptin subfamilies. The results reveal a novel serpinolytic mechanism by which enterobacterial species expressing omptins of the Pla subfamily bypass normal control of host proteolysis. doi: 10.1128/JB.00458-10

Results show that the matB fimbrial gene is expressed only in a geneticlly conserved, virulent Escherichica coli strain. Data suggest that regulation of Mat fimbria expression involves transcriptional and posttranslational events.

Research describes construction and purification of gaf gene cluster encoded GafD lectin from Escherichia coli for structure-function analysis of the fimbrial adhesisn protein. Results show that GafD is a soluble non-fusion form of the lectin and its protease-resistant subdomain exhibits receptor-binding specificity.

Results show that the collagen-binding S-layer protein CbsA is a polypeptide of 410 amino acids with a stronger collagen-binding region at the N-terminus and a weaker one at the C-terminus. Data further indicate that collagen-binding requires a crystal structure with regular array of CbsA.

The Xanthomonas capestris fimA gene encoding the bundle-forming fimbriae and cell aggregation was analyzed to characterize the role of fimbriae in Xanthomonas capestris infections. The nucleotide sequence of the fimA gene of Xanthomonas campestris was composed of two open reading frames that encode FimA and FimB proteins. Mutations in the fimA gene also impaired cell aggregation and reduced the virulence of Xanthomonas campestris cells in infected tomato leaves.