title: Microcapsule of Campylobacter fetus: chemical and physical characterization.
abstract: The antiphagocytic antigen (antigen [a]) comprising the microcapsule of a strain of Campylobacter fetus subsp. intestinalis has been purified from culture supernatants by ammonium sulfate fractionation and free-flow electrophoresis. Antigen [a] is a glycoprotein containing about 4% carbohydrate consisting of hexose, pentose, and methylpentose. The composition of the protein was typical of bacterial extramural structural proteins in its low content of basic, aromatic, and sulfur-containing amino acids. The protein had a high content of aspartic acid, threonine, glycine, and alanine. Antigen [a] had an Rf of 0.33 on polyacrylamide gel electrophoresis and a molecular weight calculated in sodium dodecyl sulfate-polyacrylamide gel electrophoresis of approximately 98,000. In contrast to its free form in culture supernatants, antigen [a] in vesicles derived from sheared cells appeared to exist in a complex with lipopolysaccharide. This complex could be dissociated by ethylenediaminetetraacetic acid or by ethylenediaminetetraacetic acid plus Triton X-100. A mutant strain that lacked a microcapsule, when incubated with soluble antigen [a] in a calcium medium, became agglutinable by monospecific [a] antiserum and showed an additional structural layer similar in appearance to the microcapsule on its cell wall. Points of similarity are emphasized between antigen [a] of C. fetus and the outer structural protein of the taxonomically related Spirillum serpens.
mesh_terms: D000371:Agglutination; D000596:Amino Acids / Q000032:analysis; D000942:Antigens, Bacterial / Q000032:analysis* / Q000302:isolation & purification; D000954:Antigens, Surface / Q000032:analysis* / Q000302:isolation & purification; D001426:Bacterial Proteins / Q000032:analysis; D002167:Campylobacter / Q000276:immunology*; D002168:Campylobacter fetus / Q000276:immunology*; D002241:Carbohydrates / Q000032:analysis; D006023:Glycoproteins / Q000032:analysis; D008970:Molecular Weight
chemical_list: D000596:Amino Acids; D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001426:Bacterial Proteins; D002241:Carbohydrates; D006023:Glycoproteins