Structure of murine Ia antigens: partial NH2-terminal amino acid sequences of products of the I-E or I-C subregion.

Abstract

Partial amino acid sequences of the Ia [immune response-associated] antigen molecule encoded by the I-E or I-C (I-EC) subregion of the major histocompatibility complex of the mouse are presented. The Ia molecule appears to be comprised of 2 noncovalently associated polypeptides. The larger subunit, .alpha., has an approximate MW of 35,000 and the smaller subunit, .beta., an approximate MW of 28,000. Several interesting homology relationships (or the lack thereof) are apparent when the Ia polypeptides from the I-EC subregion are compared with their counterparts from man and guinea pig and with the molecules encoded in the I-A subregion. Clearly the most impressive homology relationship is that seen between the .alpha. polypeptide from the I-EC subregion of mouse and its human counterpart. This is in striking contrast to the .beta. polypeptide, which bears no apparent homology to its human counterpart.