Completion of the analysis of the primary structure of the variable domain of a homogeneous rabbit antibody to type III pneumococcal polysaccharide

Abstract

The amino acid sequence between residues 70 and 116 of the V (variable) region of the H (heavy) chain derived from rabbit antibody BS-5, specific for type III pneumococcal polysaccharide, was determined. The sequence of this section of the H chain which includes the hypervariable residues 94 to about 112 was unique, although minor variant sequences present in the H chain preparation would not have been detected by the techniques used in this work. Taken together with the known sequences of the N-terminal 69 residues of H chain BS-5 (Jaton & Braun, 1972) and of the V region of the light chain (Jaton, 1974b), the data establish the complete sequence of the V domain of a rabbit immunoglobulin G. The V region of H chain BS-5 is compared with the basic sequences of the three human V region subgroups known to date, with one mouse H chain, and with guinea-pig pooled H chains. Even though chains from guinea pig and mouse clearly belong to the subgroup III of variability (VHIII), rabbit H chain BS-5 (allotypic variant a1) appears more closely related to the subgroup VHII than to the subgroups VHIII or VHI. The homology between VL and VH regions of antibody BS-5 (28%) is not greater than that observed between the VH region of antibody BS-5 and the VL regions of different rabbit antibodies.