Primary structure of a lambda Bence Jones protein (Os)

The primary structure of a human lambda type Bence-Jones protein Os was determined by analyzing amino acid sequence of the completely reduced and aminoethylated protein. Nineteen tryptic peptides covering 213 residues were isolated and 10 of these were completely sequenced. For the remaining peptides, only partial sequences or the amino acid composition were determined. All the tryptic peptides could be arranged in order on the basis of the above results and homology with other lambda chains of known sequences. The sequence of the variable region, which contains 109 residues, is homologous with those of proteins of subgroup V lambda I. The sequence of the constant region indicates that protein Os has Mcg(+), Kern(+) and Oz(-) as isotypic markers, in spite of having a unique residue at position 164.