Isolation and characterization of κ and λ chains of normal human γG-immunoglobulin

Abstract

1. 1. The heterogeneous population of normal human γG-immunoglobulin light chains consists of components belonging to two structural types, K and L, whose classification is based on the antigenic and structural characteristics of the Bence-Jones proteins. The fractionation of the light chains was accomplished by ion-exchange chromatography on SE-Sephadex at pH 3.0 in buffers containing 8 M urea. The fractions obtained by ion exchange were compared by immunodiffusion tests and by the fingerprint technique with Bence-Jones proteins of the K and L type. Using these procedures evidence was obtained that the first principal fraction emerging from the ion-exchange column represents the λ chains of normal γG-immunoglobulin while the second principal fraction involves the κ chains. 2. 2. The amino acid compositions of the κ and λ chains of normal γG-immunoglobulin are very similar. The predominant N-terminal end-groups of the κ chains were found to be aspartic and glutamic acid whereas the terminal amino groups of the λ chains are obviously blocked. The quantity of mutual contaminations in the preparation of the κ and λ chains was determined on the basis of the amino acid composition of C-terminal peptides isolated from the tryptic digest. The purity of the preparation of the λ chains was found to be 90%, the purity of the preparation of the κ chains was 84%.