Major outer membrane protein of Campylobacter fetus: physical and immunological characterization

The outer membrane proteins of Campylobacter fetus have been isolated by extraction of cell envelopes both in Triton X-100 and ethylenediaminetetraacetate (EDTA) and in sodium dodecyl sulfate (SDS). Each method yielded a major protein component, which migrated identically in SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and proved comparable in electrophoretic and molecular weight characteristics to the analagous protein from Escherichia coli. In addition, the surface of SDS-extracted C. fetus cells displayed a subunit structure similar to that observed in E. coli. The major envelope protein isolated with SDS appeared antigenically identical with one of the proteins isolated with Trition-EDTA on the basis of immunodiffusion reactions with specific antisera. Antibodies directed to the major envelope protein were not reactive in agglutination, immobilization, bactericidal, or opsonization reactions. Strains of C. fetus belonging to each of the three O serotypes possessed major envelope proteins comparable in SDS-PAGE but distinguished antigencally in a fashion paralleling the O serotype classification.