Component of the antigen processing and presentation pathway, which binds to MHC class I coupled with beta2-microglobulin/B2M. Association between TAPBPR and MHC class I occurs in the absence of a functional peptide-loading complex (PLC). Expression seems to slow down and down-regulate MHC class I surface expression. Mainly found in endoplasmic reticulum but a minority is found on the cell surface. Widely expressed.