Organization of the diversity--joining region in rabbit immunoglobulin heavy chains as revealed by cleavage of a specific methionine residue in a100 allotype.

Three anti-micrococcus antibodies of restricted heterogeneity have been isolated from the antisera of homozygous a100/a100 rabbits. Heavy chains contained an unusual methionine residue at position 87 that may correlate with the a100 specificity. From this position, the sequence of a stretch of 35-50 amino acid residues was determined, permitting the definition of variable (V), diversity(D), and joining (J) segments in rabbit Ig heavy chains, with their most probable boundaries. Rabbit D regions so defined appear to be highly variable, both in sequence and in length, which varies, in the heavy chains analyzed, between 6 and 11 residues. The J regions are highly homologous to the mouse J2 segment.