title: Studies on IgM polymerization: reassociation to non-covalently and covalently linked Fc5mu fragments.
abstract: Fc5mu fragments were purified from a trypsin digest of native IgM by gel filtration and isoelectric focusing. Polyacrylamide gel electrophoresis of Fc5mu fragments in sodium dodecyl sulphate disclosed a major and a minor band with molecules of 320,000 and 285,000 daltons, respectively. The mu chain fragments showed a molecular weight of 34,500. After reduction of the Fc5mu fragments to free mu chain fragments and J chain removal of the reducing agent by dialysis for 24 h under nitrogen in the presence of Zn ions gave non-covalently linked Fc5mu fragments. This shows that the non-covalent interactions operating between the mu chains of non-covalently linked native IgM are present in the C-terminal part of the mu chains. Additional dialysis in the presence of Zn and Cu ions resulted in the formation of covalently linked Fc5mu fragments.
mesh_terms: D000478:Alkylation; D002850:Chromatography, Gel; D003300:Copper; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007122:Immunoelectrophoresis; D007141:Immunoglobulin Fc Fragments / Q000302:isolation & purification; D007143:Immunoglobulin Heavy Chains; D007075:Immunoglobulin M; D007148:Immunoglobulin mu-Chains; D007525:Isoelectric Focusing; D011108:Polymers; D014357:Trypsin; D014461:Ultracentrifugation; D015032:Zinc
chemical_list: D007141:Immunoglobulin Fc Fragments; D007143:Immunoglobulin Heavy Chains; D007075:Immunoglobulin M; D007148:Immunoglobulin mu-Chains; D011108:Polymers; D003300:Copper; D014357:Trypsin; D015032:Zinc