Site-directed mutagenesis of Glu-141 and His-223 in Pseudomonas aeruginosa elastase: catalytic activity, processing, and protective activity of the elastase against Pseudomonas infection.

AUTOR(ES)

Kawamoto, S

RESUMO

Both Pseudomonas aeruginosa elastase and Bacillus thermoproteolyticus thermolysin are zinc metalloproteases. On the basis of the high homology of the P. aeruginosa elastase with the Bacillus thermolysin, we hypothesized that Glu-141 and His-223 are the key residues for catalytic activity of the Pseudomonas elastase. To test this possibility, we replaced Glu-141 with Asp, Gln, and Gly and His-223 with Gly, Glu, and Leu by site-directed mutagenesis. These substitutions dramatically diminished the proteolytic activities of the mutant elastases when they were expressed in Escherichia coli cells. Although these mutant elastase precursors (proelastases) were produced, no appreciable processing was observed with these mutants. The possibility that autocatalysis is involved in both the processing and activation of elastase is discussed. Furthermore, by immunizing mice with vaccines made from these mutant elastase, we were able to obtain good protection against an intraperitoneal P. aeruginosa challenge.

Documentos Relacionados

• Pseudomonas aeruginosa lasB1 mutants produce an elastase, substituted at active-site His-223, that is defective in activity, processing, and secretion.
• Site-directed mutagenesis of the catalytic residues Asp-52 and Glu-35 of chicken egg white lysozyme.
• Substitution of active-site His-223 in Pseudomonas aeruginosa elastase and expression of the mutated lasB alleles in Escherichia coli show evidence for autoproteolytic processing of proelastase.
• Synthesis, processing, and transport of Pseudomonas aeruginosa elastase.
• Improved site-directed mutagenesis method using PCR.