Reevaluation, using intact cells, of the exclusion limit and role of porin OprF in Pseudomonas aeruginosa outer membrane permeability.

AUTOR(ES)

Bellido, F

RESUMO

Earlier studies that used model membrane reconstitution methods have come to different conclusions regarding the exclusion limit of the outer membrane of Pseudomonas aeruginosa and whether OprF is the major channel-forming protein in the outer membrane. In this study, a 6.2-kbp SalI fragment, encoding only two cytoplasmic enzymes, alpha-galactosidase and sucrose hydrolase, and the inner membrane raffinose permease, was cloned behind the m-toluate-inducible tol promoter of vector pNM185 to create plasmid pFB71. P. aeruginosa strains harboring pFB71, when grown with inducer, produced both enzymes encoded by the insert and had acquired the ability to grow on the disaccharide melibiose and the trisaccharide raffinose. The rate of growth was dependent on the concentration and size of the saccharide and was decreased three- to fivefold by the absence of OprF, as examined by measuring the growth on melibiose and raffinose of an isogenic OprF-deficient omega insertion derivative, H636(pFB71). At high concentrations, di-, tri-, and tetrasaccharides could pass across the outer membrane to plasmolyze P. aeruginosa, as measured by light scattering and confirmed by electron microscopy. The initial rate kinetics of light-scattering changes were dependent on the size of the saccharide being used. Furthermore, the rates of change in light scattering due to raffinose and stachyose uptake across the outer membrane for strain H636 were fivefold or more lower than for its OprF-sufficient parent H103. These data are consistent with model membrane studies showing that OprF is the most predominant porin for compounds larger than disaccharides in P. aeruginosa and suggest that the exclusion limit for this porin and the outer membrane is greater than the size of a tetrasaccharide. In addition, these data confirmed the existence of other porins with a predominant function in monosaccharide uptake and a more minor function in the uptake of larger saccharides.

Documentos Relacionados

• Epitope mapping of the Pseudomonas aeruginosa major outer membrane porin protein OprF.
• Analysis of the Pseudomonas aeruginosa major outer membrane protein OprF by use of truncated OprF derivatives and monoclonal antibodies.
• Conservation of the gene for outer membrane protein OprF in the family Pseudomonadaceae: sequence of the Pseudomonas syringae oprF gene.
• Secondary structure of the outer membrane proteins OmpA of Escherichia coli and OprF of Pseudomonas aeruginosa.
• The Amino Terminus of Pseudomonas aeruginosa Outer Membrane Protein OprF Forms Channels in Lipid Bilayer Membranes: Correlation with a Three-Dimensional Model