Immunoglobulin kappa-chains. Comparative sequences in selected stretches of Bence-Jones proteins.
Three type K Bence-Jones proteins have been fully reduced and carboxymethylated with high-specific-activity iodo[(14)C]acetate. A tryptic digest and a chymotryptic digest of each protein were fractionated on a Sephadex column and the radioactive peptides were purified by paper electrophoresis. All the proteins studied had five unique carboxymethylated cysteine sequences. Three of these were identical with the exception of a single substitution, and two had some variations. The common peptides could be placed in the C-terminal half of the molecule. The variations around the other two half-cysteine residues provided information about the nature of the variability of the primary sequence of immunoglobulin kappa-chains. The results are consistent with the hypothesis that the chains derive from a common ancestor by somatic mutation of a small number of genes or by gene doubling and selection in the course of evolution. The isolation of the N-terminal peptide in methionine-containing Bence-Jones proteins is also described.
D000595:Amino Acid Sequence; D001536:Bence Jones Protein / Q000032:analysis*; D002247:Carbon Isotopes; D002918:Chymotrypsin; D004586:Electrophoresis; D007461:Iodoacetates; D008967:Molecular Biology; D010455:Peptides / Q000032:analysis*; D013450:Sulfones; D014357:Trypsin; D005719:gamma-Globulins / Q000032:analysis*
D002247:Carbon Isotopes; D007461:Iodoacetates; D010455:Peptides; D013450:Sulfones; D005719:gamma-Globulins; D001536:Bence Jones Protein; D002918:Chymotrypsin; D014357:Trypsin