A Possible Precursor of Immunoglobulin Light Chains

IMMUNOGLOBULIN light chains are synthesized in heterologous cell-free systems from reticulocytes1 and Krebs II ascites cells2, and in reconstituted homologous systems from lymph nodes3,4 and myeloma tumours5,6. Although the synthesis appeared to be essentially faithful, absolute identity with authentic light chains was not demonstrated and some small differences were observed. We report here a clear discrepancy between the product of certain cell-free reactions and authentic light chain. With the product of other cell-free reactions no such discrepancy is seen. We propose that light chains are initially synthesized as a precursor of slightly higher molecular weight and subsequently converted into the authentic product.