Structural studies on the murine Ia alloantigens. IV. NH ₂-terminal sequence analysis of allelic products of the I-A and I-E/C subregions

Murine Ia alloantigens encoded by the I-A and I-E/C subregions were isolated from radiolabeled splenic lysates and examined by NH ₂-terminal sequence analysis. Haplotype-associated sequence variation was detected in the β, but not α, subunits of both the A and E/C alloantigens. The A β-polypeptides from k and b haplotypes show four differences in the 12 positions compared, whereas the E/C β-polypeptides from k and r haplotypes show two differences in the 13 positions compared. No sequence variation was detected between the A(k) and A(b) α-chains (six positions compared) or between the E/C(k) and E/C(r) α-chains (11 positions compared). Homology relationships between these murine Ia alloantigens and the human Ia (DR) alloantigens are also presented.