Interactions of a secreted Pseudomonas aeruginosa aminopeptidase with bacterial outer membrane molecules: characterization and implications for bacterial pathogenic phenotypes.

Abstract

The protein Pseudomonas aeruginosa aminopeptidase (PaAP) is secreted by the opportunistic, Gram-negative bacterial pathogen Pseudomonas aeruginosa. PaAP expression appears to be upregulated in clinical isolates of P. aeruginosa, especially in strains found in the lungs of cystic fibrosis patients, likely indicating that it serves a role in the development of pathogenic phenotypes. However, the function(s) that PaAP serves in pathogenic contexts are as yet unknown, as are the mechanisms by which PaAP accomplishes them. This work seeks to identify molecules of the Gram negative outer membrane with which PaAP interacts in order to understand the role that PaAP plays in the establishment and maintenance of P. aeruginosa infections. Particular attention is given to determining whether PaAP interacts with lipopolysaccharide (LPS), which is the major constituent of the Gram negative outer membrane and a potent toxin and immune system agonist. To accomplish this goal, a range of biochemical analyses are used, particularly immunochemistry techniques. While results from these assays are preliminary, our findings suggest that PaAP does not interact with P. aeruginosa LPS, suggesting that proteins or non-LPS saccharides are the primary interaction partners of PaAP in the outer membrane.