Antibodies to an NH2-terminal fragment of betaS globin. II. Specificity and isolation of antibodies for the sickle mutation.

The immunochemical specificity of an antiserum produced to an NH2-terminal 55-residue polypeptide fragment of the betaS globin, betaS(1-55), was analyzed with a radioimmunoassay using the radioiodinated fragment as a tracer. These studies show that most of the antibodies have comparable reactivity with betaS(1-55), betaA(1-55), betaS globin, betaA globin, HbS, and HbA. However, the antiserum contains some antibodies which react only with the species derived from HbS. These "S" -specific antibodies were isolated by absorption of the serum on a column of betaA(1-55) coupled covalently to Sepharose. The S-specific antibodies have markedly diminished reaction with betaA(1-55) and HbA. The S specificity was localized to the valine substitution at position 6 of the beta globin, as shown by inhibition of the binding of the radiolabeled fragment to S-specific antibodies by the synthetic peptide betaS(1-13). These antibodies, which appear monospecific, can be used to study the conformation of the NH2-terminal region of the beta chain of HbS.