ALLELIC VARIATION IN THE MOUSE TAP-1 AND TAP-2 TRANSPORTER GENES

The TAP1 and TAP2 proteins form a heterodimer that transports short pe ptides from the cytosol into the endoplasmic reticulum lumen, Extensiv e allelic polymorphism of the rat TAP transporter has been shown to af fect the repertoire of peptides presented by MHC class I molecules, St ructural polymorphism in the human TAP genes is much more limited and has not been observed to have functional consequences, We have examine d the polymorphism in mouse TAP1 and TAP2 in inbred mice, While the nu mber of polymorphic positions in these molecules is more similar to th at in human than to that in the rat, all strains examined have a struc turally unique TAP transporter, suggesting the possibility of function al polymorphism, Furthermore, allelic variations in the mouse transpor ter are predominantly located in or adjacent to membrane-spanning doma ins, although no significant bias in the ratio of nonsynonymous to syn onymous substitutions is observed, We also report that mouse TAP1 begi ns 172 amino acids upstream of the previously published start site and report the genomic organization of mouse Tap-1 and Tap-2.