Transporters from H-2b, H-2d, H-2s, H-2k, and H-2g7 (NOD/Lt) haplotype translocate similar sets of peptides.

The TAP complex transports peptides from the cytosol into the lumen of the endoplasmic reticulum for presentation by major histocompatibility complex class I molecules. A limited degree of sequence polymorphism has been observed for the mouse TAP1 and TAP2 genes by restriction fragment length polymorphism and sequence analysis. However, functional polymorphism of the TAP transporter has thus far been observed for the rat only. Here we examine the effect of TAP polymorphism on ATP dependency and peptide specificity of TAP-mediated peptide transport and show that, in the mouse, polymorphism in TAP genes does not measurably alter the function of their gene products. We conclude that TAP polymorphism is unlikely to contribute to the development of autoimmune diseases and that, in the mouse, the specificity of the TAP transporter is matched to that of the F pocket of the class I molecules for which it provides the peptide substrates.