The disulphide bridges of immunoglobulin ϰ-chains

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Abstract
The arrangement of the disulphide bridges of the major component of the light chains of immuno-globulins ([chi] -chains) has been studied in the Bence-Jones proteins. Three disulphide bridges have been found. An interchain bridge at the C-terminus has been shown to occur in the dimers of all the proteins studied and was characterized by symmetrical peptides. In the monomer form, the C-terminal halfcystine of the corresponding peptides was linked to a lone half-cystine residue. A second common disulphide-bridge peptide in which a single amino acid difference could be related to the Inv factors of the individual proteins was found in Bence-Jones proteins and in the [chi]-chains of normal and abnormal immunoglobulins. Peptides characteristic of a 3rd disulphide bridge studied in three specimens were found to have differences in some residues, but also striking similarities. A methionine peptide has also been characterized in 2 specimens as a by-product of the technique employed. It is suggested that a general manner of folding may be a common feature of the heterogeneous population of [chi]-chains: one bridge which folds an invariable stretch of the chain, another bridge which folds a stretch that varies from protein to protein, and a bridge at the C-terminus which is the interchain link.