Site-directed mutagenesis of the Pseudomonas aeruginosa cytotoxin for probing toxic activity.

The location of amino acids with direct influence on toxic activity in the pore-forming cytotoxin from Pseudomonas aeruginosa was tested by site-directed mutagenesis. Mutant fragments obtained by the polymerase-chain reaction were subcloned into a cytotoxin gene-bearing plasmid to minimize the possibility of amplification error. Our data suggest an important role of cysteines for toxic activity of cytotoxin. Furthermore, domain-facilitating-binding to plasma membranes is located on the C-terminal side of Cys215.