Sequence variability of rabbit antibody light chains. Familial occurrence of n-terminal sequence differences between b4 and b9 light chains.

Amino acid sequence analyses of the IgG light (L) chains from selected members of a rabbit family with allotypes b4 and b9 showed N-terminal substitutions that segregated with the b4 allotype. The L chains of allotype b4 had tyrosine at step 2, whereas this residue was absent from that step in the b9 L chains. Steps 12 and 13 of b4 L chains yielded a high percentage of glutamic acid, whereas a low percentage was observed for the b9 L chains. These tyrosine and glutamic acid substitutions were observed with the same frequency in L chains from homogeneous antibodies as in the L chains of the IgG samples. The data suggest that, in the family studied, separate and distinct V-region gene complexes are linked to the b4 and b9 allotypic genes.