PSEUDOMONAS-AERUGINOSA CYTOTOXIN - THE ASP(197)-GLY-ASP-TYR-HIS-TYR-HIS-TYR(202) CONTAINING LOOP IS CRITICAL FOR PLASMA-MEMBRANE BINDING

The cytotoxin from Pseudomonas aeruginosa is a pore-forming toxin that binds specifically to water channel-related molecules of the erythroc yte membrane. Here, we have defined a domain, Asp(197)-Gly-Asp-Tyr-His -Tyr(202) of the cytotoxin, to be essential for receptor binding. Cyto toxin point mutants from the recombinant gene carrying substitutions i n the domain were characterized in terms of inhibiting the binding of radioiodinated natural cytotoxin to rat erythrocyte and producing cyto toxic effects in human granulocytes. A synthetic peptide representing residues 191-211 of the cytotoxin acted as a competitive inhibitor at a concentration of 10(-5) M. In contrast, two other cytotoxin-specific peptides were inactive. Structure prediction of the binding sequence shows a loop structure with similarities to the sequence around His(33 2) in Aeromonas aerolysin essential to receptor binding.