Differences in fragmentation between bound and unbound bovine secretory component suggest a model for its interaction with polymeric immunoglobulin.
Unbound bovine secretory component was cleaved into two-domain and one-domain fragments by trypsin within 1 h. Bovine secretory component covalently bound to bovine IgA dimer, as in secretory IgA, was much more resistant to fragmentation, which did not proceed beyond the three-domain stage even after 5 h. Bovine secretory component non-covalently bound to bovine IgM or to human IgM or IgA polymer was also relatively resistant to fragmentation, which again was largely arrested at the three-domain stage. A model for the binding of secretory component to polymeric immunoglobulin is proposed.
D000818:Animals; D001704:Biopolymers; D002417:Cattle; D004591:Electrophoresis, Polyacrylamide Gel; D007070:Immunoglobulin A / Q000276:immunology*; D007128:Immunoglobulin Fragments / Q000276:immunology*; D007075:Immunoglobulin M / Q000276:immunology*; D008958:Models, Molecular; D010446:Peptide Fragments / Q000276:immunology*; D011485:Protein Binding; D012635:Secretory Component / Q000276:immunology*; D014357:Trypsin
D001704:Biopolymers; D007070:Immunoglobulin A; D007128:Immunoglobulin Fragments; D007075:Immunoglobulin M; D010446:Peptide Fragments; D012635:Secretory Component; D014357:Trypsin