Amino acid sequence of the variable region of an unusual lambda-type human Bence Jones protein (Lee)

The variable portion of a human lambda-type Bence Jones protein (Lee) has been prepared by limited tryptic digestion. Its amino acid sequence is determined from analysis of tryptic peptides, CNBr cleavage fragments prepared from the reduced-aminoethylated protein. Peptides are aligned by homology to other lambda-type proteins. The Lee L-chain has an unusual extension of two amino acid residues (Val-Thr) at the N-terminus. An idiotypic antibody of Lee can react with two other lambda-type Bence Jones proteins, Meg (V lambda IV) and Cap (V lambda III). Application of the principle of Chou and Fasman to the sequence data indicates that two portions on the surface of the V-region have identical secondary structures similar to the portions of the Meg and Cap lambda-chains. This appears to relate to the idiotypic similarities of the three proteins.