On the localisation of antigenic determinants in a Bence Jones protein

Abstract

1. 1. The presence of a low molecular weight protein (1.2 S), having antigenic determinants in common with the homologous Bence Jones protein (3.4 S), has been observed in the urine of a patient with multiple myeloma. Its amino acid composition and α-NH2-terminal amino acid residue make it likely that the 1.2 S component is a protein representing the NH2-terminal, variable, moiety of the Bence Jones protein.

2. 2. After digesting Bence Jones protein (type K, InV(a−)) with pepsin, an antigenically active peptide could be isolated via immunoprecipitation with the homologous antiserum. From its amino acid composition this peptide appears to be located at the COOH-terminal end of the Bence Jones protein, i.e. in the constant part of the polypeptide chain; it must perforce contain the group-specific antigenic determinant.