Isolation of major histocompatibility complex class I cDNA from pink salmon (Oncorhynchus gorbuscha)

An MHC class I cDNA clone was isolated from pink salmon (Oncorhynchus gorbuscha). Eight amino acids, which have been shown in mammals to bind main-chain atoms of peptides, are well conserved in the salmon alpha 1 and alpha 2 domains. Nine amino acids in the alpha 3 domain are classified by Williams and Barclay (Ref. 1. Ann. Rev. Immunol. 6:381-405, 1988) as signature immunoglobulin superfamily residues. The pink salmon MHC class I extracellular domains show 84.2% amino acid identity with those of Atlantic salmon (Sasa p30). polymorphism of the MHC class I alpha 1 domain was determined using PCR with genomic DNA from 12 fish. Sixteen variants were identified with most diversity concentrated in those amino acids that bind directly to peptides in mammalian class I molecules. Non-synonymous substitutions predominate over synonymous ones in the codons encoding these polymorphic residues.