title: Studies on the reduction of a human 19S immunoglobulin M.
abstract: 1. Reduction of a 19s immunoglobulin M with 3mm-mercaptoethanol or 0.05-0.5mm-dithiothreitol followed by alkylation gave sedimentation patterns indicating products compatible with structures consisting of one, two, three, four and five 7s sub-units. This supports the concept of a five-sub-unit structure for immunoglobulin M. 2. Reduction with 0.125mm-dithiothreitol or 20mm-cysteine produced 7s sub-units that could not be dissociated into chains in m-propionic acid. 3. By labelling (with iodo[2-(14)C]acetic acid) the thiol groups liberated during reduction with 0.125mm-dithiothreitol, it was possible to identify the tryptic peptides involved in the disulphide bridges that link the 7s sub-units together (inter-sub-unit bridges). 4. By further reducing and labelling (with iodo[2-(14)C]acetic acid) the 7s sub-units produced by 0.125mm-dithiothreitol, it was possible to identify tryptic peptides derived from intra-sub-unit bridges. 5. Sub-units produced by reduction with 20mm-cysteine proved to be unsuitable for distinguishing between inter-sub-unit bridges and intra-sub-unit bridges. 6. The possible arrangement of the interchain disulphide bridges was deduced.
mesh_terms: D000478:Alkylation; D000818:Animals; D000941:Antigens; D001536:Bence Jones Protein; D002241:Carbohydrates; D002247:Carbon Isotopes; D055598:Chemical Phenomena; D002621:Chemistry; D002850:Chromatography, Gel; D003545:Cysteine; D003911:Dextrans; D004586:Electrophoresis; D006801:Humans; D007106:Immune Sera; D007122:Immunoelectrophoresis; D007075:Immunoglobulin M; D007461:Iodoacetates; D008623:Mercaptoethanol; D008961:Models, Structural; D010084:Oxidation-Reduction; D010455:Peptides; D012756:Sheep; D013438:Sulfhydryl Compounds; D013440:Sulfides; D014461:Ultracentrifugation; D008258:Waldenstrom Macroglobulinemia / Q000097:blood
chemical_list: D000941:Antigens; D002241:Carbohydrates; D002247:Carbon Isotopes; D003911:Dextrans; D007106:Immune Sera; D007075:Immunoglobulin M; D007461:Iodoacetates; D010455:Peptides; D013438:Sulfhydryl Compounds; D013440:Sulfides; D008623:Mercaptoethanol; D001536:Bence Jones Protein; D003545:Cysteine