Domain structures of cell surface glycopeptides encoded by class I and class II beta genes of the major histocompatibility complex.

Published sequence data of MHC genes, cDNAs and MHC products were analyzed for their sequence homologies. Alignment statistics revealed that class I gene products consist of four mutually homologous domains, and that class II beta gene products is composed of three mutually homologous domains. Not only extracellular domains but also newly discovered C-terminal shorter domains of class I and class II beta gene products were found to have evolved from a one-domain-long beta 2-microglobulin-like protein by repeated exon duplications and splittings.