'Pseudomonas aeruginosa' LasA Protein: Purification, Characterization, and ItsRole in Enhancement of Elastase Activity

摘要

Pseudomonas aeruginosa secretes at lest three proteases, including elastase,which have been implicated as possible virulence factors of this opportunistic pathogen. Elastase has been recognized as a unique protease which has an expanded substrate to include elastin, a major component of lung, vascular and connective tissues. In cystic fibrosis patients, P.aeruginosa elastase and neutrophil elastase have been implicated in the tissue destruction associated with this disease as a result of chronic infection. These studies have resulted in the purification of a 22-kilodalton protein from the culture supernatant fraction of P.aeruginosa which enhances the elastrolytic activity of purified P.aeruginosa elastase. N-terminal sequence analysis identified the protein as a fragment of the LasA gene product. The purified LasA fragment has extremely restrictive proteolytic activity and minimal elastolytic activity. Although LasA does not enhance the proteolytic activity of elastase against Azocoll substrate, it enhances the elastrolytic activity of elastase more than 25-fold. The LasA fragment was found to also enhance the elastolytic activities of thermolysin, human neutrophil elastase, and proteinase K. Enhancement of elastolytic activity was found to be the result of a modification of the elastin substrate, not due to a modification of elastase as had previously been suggested. (ttl)