title: Size and structure of the cholera toxin molecule and its subunits.
abstract: Cholera toxin (choleragen) dissociated into two types of subunit with molecular weights estimated to be 28,000 daltons (A) and 11,000 daltons (B); this dissociation was effected by gel filtration at acid pH with or without urea. Subunit A could be separated into two fragments, A1 (23,000 daltons) and A2 (about 2,500 daltons), after reduction and alkylation. Choleragenoid (68,000 daltons) appeared to be a polymerized form of subunit B. A-specific antigen was found in choleragen as well as in A1 and A2, while B-specific antigen was found in both choleragen and choleragenoid. In electron micrographs, the toxin molecule appeared as a particle of uniform size consisting of subunits in V- or Y-shape and in ring form. The dimensions coincided with the values calculated from the molecular weights.
mesh_terms: D000942:Antigens, Bacterial; D001426:Bacterial Proteins / Q000032:analysis; D002850:Chromatography, Gel; D005779:Immunodiffusion; D007122:Immunoelectrophoresis; D008854:Microscopy, Electron; D008970:Molecular Weight; D014734:Vibrio cholerae / Q000276:immunology
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins