Partial N-terminal amino acid sequences of guinea pig classic histocompatibility antigens

Partial N-terminal amino acid sequences were determined by microsequencing for three of the guinea pig GPLA-B classic histocompatibility antigens, which are presumably allelic products. The sequences of GPLA-B.1 derived from the noncongenic inbred strain 2 and strain 13 animals showed no differences a their N-termini, suggesting that these molecules are chemically as well as serologically identical. Two residues, isoleucine and leucine, were found at position 5 of the sequence of GPLA-B.1, suggesting that GPLA-S, the product of the second classic histocompatibility locus, was being cosequenced. GPLA-B.2 and GPLA-B.3 antigens showed distinct sequence differences from GPLA-B.1 and from each other. The sequences of GPLA-B.3 derived from a random-bred guinea pig and from the inbred DHCBA strain showed no differences and showed a possible species specific residue. All sequences showed significant homology with histocompatibility antigens of other species, suggesting a common evolutionary origin.