title: Sensitivity of Escherichia coli to cloacin DF13 involves the major outer membrane protein OmpF.
abstract: Fourteen spontaneous cloacin DF13-insensitive mutants of an Escherichia coli strain expressing the aerobactin-cloacin DF13 receptor protein IutA were isolated. The mutants fell into three classes on the basis of outer membrane profiles analyzed by electrophoresis in denaturing polyacrylamide gels. The most frequent class lacked the IutA protein and was unable to bind cloacin DF13 or aerobactin. A second class of mutants had lost protein species corresponding in size to the porin proteins OmpF and OmpC. To determine which porin was required for the bactericidal activity of cloacin DF13, defined strains with mutations at the ompB (ompR envZ) locus were transformed with a recombinant plasmid carrying the iutA gene and screened for cloacin DF13 sensitivity. OmpF- strains, whether OmpC+ or OmpC-, were insensitive to cloacin DF13, indicating involvement of the OmpF protein in cloacin DF13 killing. An OmpC- OmpF+ strain, on the other hand, was more sensitive than the wild-type parent strain, probably because of compensatory overexpression of OmpF. The third class of cloacin DF13-insensitive mutant had lost an outer membrane protein of approximately 31 kDa. The nature and function of this protein are not yet known, but it is not the protease OmpT. Mutants of classes 2 and 3 bound cloacin DF13 and aerobactin as effectively as the cloacin DF13-sensitive parental strain, indicating that they remained IutA+. We propose that these mutants (more accurately described as cloacin DF13 tolerant) are defective in translocation of the active portion of cloacin DF13 across the bacterial membranes.
authors.affiliation: Department of Genetics, University of Leicester, England.
authors.forename: K G
authors.initials: KG
authors.lastname: Wooldridge
authors.forename: P H
authors.initials: PH
authors.lastname: Williams
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D001426:Bacterial Proteins / Q000494:pharmacology*; D001430:Bacteriocins / Q000494:pharmacology*; D004361:Drug Tolerance; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics; D029968:Escherichia coli Proteins; D006877:Hydroxamic Acids / Q000378:metabolism; D007502:Iron Chelating Agents / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D011971:Receptors, Immunologic / Q000032:analysis
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D001430:Bacteriocins; D029968:Escherichia coli Proteins; D006877:Hydroxamic Acids; D007502:Iron Chelating Agents; D011971:Receptors, Immunologic; C034506:aerobactin receptor; C052368:cloacin DF13-encoded bacteriocin release protein, E coli; C031819:aerobactin