A mutant of P. aeruginosa severely deficient in outer membrane protein F levels was isolated by screening heavily mutagenized strains for membrane protein alterations on sodium dodecyl sulphate-polyacrylamide gel electrophoresis. To provide a basis for phenotypic comparison, three independent spontaneous revertants with normal protein F levels were isolated. Neither the protein F-deficient mutant nor its revertants had gross surface alterations as judged by their sensitivities to 31 phages with diverse receptors and their low degrees of leakage of periplasmic β-lactamase into the supernatant. Outer membrane permeability was measured in whole cells by examining the rates of hydrolysis of a chromogenic β-lactam, nitrocefin, by periplasmic RP1-encoded β-lactamase. It was found that the outer membrane permeabilities of wild-type and protein F revertant strains were similar, but low when compared with those of Escherichia coli and an antibiotic-supersusceptible mutant Z61 of P. aeruginosa. The loss of protein F caused a further significant decrease in outer membrane permeability. The results suggest that protein F is a pore-forming protein in vivo and that only a small proportion, as few as 1 in 400, of the protein F molecules form active functional channels in vivo.
|Number of pages||5|
|Journal||Journal of bacteriology|
|Publication status||Published - 1 Jan 1983|
ASJC Scopus subject areas
- Molecular Biology