title: Disulfide-bonded outer membrane proteins in the genus Legionella.
abstract: Legionella pneumophila and related species were examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis for outer membrane proteins. Of the 10 species examined, 9 contained a 24-kilodalton (kDa) major outer membrane protein (MOMP) that was resolvable only when outer membrane material was heated in the presence of 2-mercaptoethanol. Labeling studies with [35S]cysteine indicated that the protein contained cysteine, and disulfide cross-linking of the unreduced complex was demonstrated by labeling with iodoacetamide. The unreduced outer membrane preparation contained peptidoglycan, and after treatment with lysozyme to remove peptidoglycan, a protein complex of 95 kDa was observed by sodium dodecyl sulfate polyacrylamide gel electrophoresis in the absence of 2-mercaptoethanol. Reduction of the 95-kDa complex yielded 24-kDa monomers, suggesting that the 95-kDa complex was composed of four subunits. The 24-kDa MOMP from L. pneumophila was purified, and antibody produced to this protein cross-reacted with all species of Legionella as determined from an immunoblot of a sodium dodecyl sulfate gel. Only serogroup 1 strains of L. bozemanii lacked the 24-kDa MOMP and showed no cross-reactivity. These results suggest that the 24-kDa MOMP common to most species of Legionella contains a genus-specific epitope.
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000032:analysis*; D004220:Disulfides; D004591:Electrophoresis, Polyacrylamide Gel; D007875:Legionella / Q000032:analysis* / Q000276:immunology; D010457:Peptidoglycan / Q000032:analysis
chemical_list: D001425:Bacterial Outer Membrane Proteins; D004220:Disulfides; D010457:Peptidoglycan