Partial amino acid sequences of marine Ia antigens of the I-ECd subregion

Partial N-terminal amino acid sequences of the Ia molecule encoded by theI-E orI-C (I-EC) subregion of theH- 2^d haplotype are presented. Several homology relationships are apparent when these sequences are compared to the gene products of the mouseI- EC^k andI-A subregions and to their human and guinea pig counterparts. The polypeptide differs from the EC ^k polypeptide in two of the seven positions at which they can be compared and shows moderate homology with its human p29 counterpart. The polypeptide is identical to the EC ^k polypeptide in the eight positions which can be compared and is highly homologous to the human p34 polypeptide. The genetic implications of these observations are discussed.Abbreviations used in this paper are SDS-PAGE sodium dodecyl sulphate polyacrylamide gel electrophoresis - PTH-amino acid phenylthiohydantoin amino acid - I-EC I-E or I-C (subregion of the I region)