title: The Fab/c fragment of IgG produced by cleavage at cyanocysteine residues.
abstract: The intra- and inter-heavy chain disulfides of rabbit IgG were cleaved by mild reduction with either dithiothreitol or sulfite and cyanocysteines generated by treatment with either 2-nitro-5-thiocyanobenzoic acid or KCN, respectively. When cleavage occurs at a cyanocysteine residue in the hinge region of one heavy chain alone the Fab/c fragment is produced. Fab/c was also produced by papain digestion of IgG. Fab/c made by papain digestion was able to active complement in haemolytic assays; this activity was lost after cleavage of its accessible disulfide bonds. Fab/c made by cyanylysis of sulfite-reduced IgG was also active in these assays, but Fab/c made by cyanylysis of dithiothreitol-reduced IgG was not. Treatment of the latter fragment with cysteine and cystine resulted in partial reformation of cleaved disulfide bonds. Fab/c was also made from human IgG and from murine IgG2a and IgG2b.
authors.affiliation: Department of Biochemistry, University of Sydney, N.S.W., Australia.
authors.forename: B D
authors.initials: BD
authors.lastname: Wines
authors.forename: S B
authors.initials: SB
authors.lastname: Easterbrook-Smith
mesh_terms: D000818:Animals; D002850:Chromatography, Gel; D015941:Complement Hemolytic Activity Assay; D003602:Cytotoxicity, Immunologic; D004229:Dithiothreitol / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D007140:Immunoglobulin Fab Fragments / Q000138:chemical synthesis* / Q000276:immunology; D007074:Immunoglobulin G / Q000378:metabolism*; D066298:In Vitro Techniques; D010206:Papain / Q000494:pharmacology; D011190:Potassium Cyanide / Q000494:pharmacology; D011817:Rabbits; D013439:Sulfhydryl Reagents / Q000494:pharmacology*; D013861:Thiocyanates / Q000494:pharmacology
chemical_list: D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D013439:Sulfhydryl Reagents; D013861:Thiocyanates; D010206:Papain; D011190:Potassium Cyanide; C008658:2-nitro-5-thiocyanobenzoic acid; D004229:Dithiothreitol