The carboxy-terminal peptides of in vitro precursor and in vivo mature kappa light chains are identical.

Protein structural analysis of several precursor light chains indicates that these in vitro products include a cysteine-containing tryptic peptide that is indistinguishable from the carboxy-terminal tryptic tripeptide present in in vivo mature kappa light chains. It is concluded that although in vitro precursor light chains contain an additional amino-terminal sequence, their carboxy-terminus is the same as that found in in vivo mature light chains.