Human single-chain urokinase is activated by the omptins PgtE of Salmonella enterica and Pla of Yersinia pestis despite mutations of active site residues.

Fibrinolysis is important in cell migration and tightly regulated by specific inhibitors and activators; of the latter, urokinase (uPA) associates with enhancement of cell migration. Active uPA is formed through cleavage of the single-chain uPA (scuPA). The Salmonella enterica strain 14028R cleaved human scuPA at the peptide bond Lys158-Ile159, the site cleaved also by the physiological activator human plasmin.

The omptins of Yersinia pestis and Salmonella enterica cleave the reactive center loop of plasminogen activator inhibitor 1.

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.

Expression of Pls (plasmin sensitive) in Staphylococcus aureus negative for pls reduces adherence and cellular invasion and acts by steric hindrance.

Background: The methicillin-resistant Staphylococcus aureus (MRSA) surface protein Pls (plasmin sensitive) reduces adhesion to host proteins and cellular invasiveness by an unknown mechanism that requires Pls expression. Here, we tested the effect of Pls expression using different pls-negative backgrounds.

Methods: Three pls-negative strains (the methicillin-susceptible Staphylococcus aureus strains Cowan I and 6850 and the MRSA strain ST239-635/93, which harbors staphylococcal cassette chromosome [SCC] mec type III) were transformed.

Staphylococcal chromosomal cassette mec type I, spa type, and expression of Pls are determinants of reduced cellular invasiveness of methicillin-resistant Staphylococcus aureus isolates.

We have shown previously that pls, which codes for the surface protein Pls of methicillin-resistant Staphylococcus aureus (MRSA), reduces adhesion to immobilized fibronectin, fibrinogen, laminin, and immunoglobulin G as well as invasion of host cells. Here, we tested a collection of 66 clinical MRSA isolates--48 negative for pls/Pls (pls(-)/Pls(-)), 15 positive for pls/Pls (pls(+)/Pls(+)), and 3 harboring the pls gene but not expressing Pls (pls(+)/Pls(-))--for cellular invasiveness. Invasion of 293 cells by pls(+)/Pls(+) strains was lower than that by the pls(-)/Pls(-) strains (median [range], 36% [22%-70%] vs.

The surface protein Pls of methicillin-resistant Staphylococcus aureus is a virulence factor in septic arthritis.

Pls, a surface protein of certain methicillin-resistant Staphylococcus aureus strains, is associated with poor bacterial adherence to solid-phase fibronectin and immunoglobulin G, as well as with reduced invasion of cultured epithelial cells. Here the importance of Pls for the development of septic arthritis and sepsis was investigated by using a mouse model. Mice inoculated with a pls knockout mutant developed a much milder arthritis and showed less grave weight reduction than mice infected with the wild-type Pls(+) clinical isolate.

The pls gene found in methicillin-resistant Staphylococcus aureus strains is common in clinical isolates of Staphylococcus sciuri.

pls, a gene found in type I staphylococcal cassette chromosome mec (SCCmec) regions of methicillin-resistant Staphylococcus aureus strains, was present in 12 of the 15 human clinical Staphylococcus sciuri isolates studied. Pls was expressed in the S. sciuri isolates, although at a lower level than in S.

Reduced adherence and host cell invasion by methicillin-resistant Staphylococcus aureus expressing the surface protein Pls.

Pls, the surface protein of methicillin-resistant Staphylococcus aureus (MRSA), prevents adhesion of clinical strain 1061 to immobilized fibronectin (Fn) and immunoglobulin G (IgG). Invasion of mammalian cells by S. aureus depends on Fn-mediated binding of staphylococcal Fn-binding proteins to host cell beta (1)-integrins.