The Effect of Sodium Dodecylsulfate on Intact and Insoluble Papain Hydrolyzed Immune Globulin

Summary Limited hydrolysis of rabbit immune globulin by insoluble papain converts the γ-globulin into a form that can be fragmented by reduction. After undergoing this critical proteolysis the immune globulin could be dissociated into subunits by sodium dodecylsulfate acting at pH 6.8 in the absence of reducing agents. The two major products of this dissociation were a soluble component having a molecular weight of about 85,000, which could be further fragmented by reduction, and a component which was insoluble in aqueous buffer solutions. The detergent sodium dodecylsulfate was shown to reversibly inhibit antigen-antibody precipitation. Removal of detergent from intact immune globulin restored its ability to precipitate homologous antigen. Likewise, removal of detergent from the products of the consecutive action of insoluble papain and dodecylsulfate on immune globulin resulted in the recovery of a component, having a molecular weight of 85,000, which still specifically precipitated with antigen. Thus this component appeared to be immunologically divalent. Treatment of immune globulin with either insoluble papain or detergent alone did not appreciably alter its ability to “fix” components of the complement system upon interaction with antigen. In contrast, the component having a molecular weight of 85,000, obtained by the consecutive action of papain and detergent, did not “fix” complement upon precipitation with its homologous antigen. Thus the detergent dissociation of hydrolyzed immune globulin appeared to be along functional lines. The absence of the Fragment III moiety of γ-globulin from the component having a molecular weight of 85,000 was demonstrated by antigenic analysis and by sedimentation analysis of the reductively dissolved immune precipitates formed by its reaction with antigen. The dissociation of hydrolyzed immune globulin was found to proceed slowly in the presence of detergent. The yield of the component of MW = 85,000 was greatest after incubation for 14 to 16 hr. Dissociation was inhibited by N-ethylmaleimide, iodoacetamide, and p-chloromercuribenzoate, suggesting the involvement of the disulfide bonds of the globulin in this process.