The Binding of Murine IgM to Staphylococcal A Protein

Abstract
The binding of staphylococcal A protein [Staph A] to murine immunoglobulins [Ig] was previously thought to be restricted to the IgG2 and IgG3 classes. In this study, 5 IgM proteins were assessed for binding, and of these, 1 showed marked Staph A binding. Pepsin digestion of this IgM molecule produced several different sized fragments, and the binding studies with these fragments indicated that the binding site is in the CH2 [H chain constant region 2] domain.