Pronase digestion of human IgG and Fcδ

Abstract The susceptibility of human Fcδ and IgG to proteolysis with pronase under conditions similar to those used for the removal of Ig from lymphocyte membranes has been studied. This treatment did not effect proteolysis of the Fcδ fragment but the IgG was rapidly digested to yield Fab, Fc and Fc' fragments. The Fab fragment is resistant to further proteolysis but the Fc and Fc' fragments are progressively degraded to small peptides. The Fc and Fc' products isolated from a 3 hr digest were shown to be composed of residues 225 (Thr)-466 (Glu) and 345 (Glu)-432 (Ala). Implications of these findings for the mode of action of enzyme removal of lymphocyte membrane Ig are discussed.