Complete nucleotide sequence of primitive vertebrate immunoglobulin light chain genes

Antibody to Heterodontus francisci (horned shark) immunoglobulin light chain was used to screen a spleen cDNA expression library, and recombinant clones encoding light chain genes were isolated. The complete sequences of the mature coding regions of two light chain genes in this phylogenetically distant vertebrate have been determined and are reported here. Comparisons of the sequences are consistent with the presence of mammalian-like framework and complementarity-determining regions. The predicted amino acid sequences of the genes are more related to mammalian λ than to κ light chains. The nucleotide sequences of the genes are most related to mammalian T-cell antigen receptor β chain. Heterodontus light chain genes may reflect characteristics of the common ancestor of immunoglobulin and T-cell antigen receptors before its evolutionary diversification.