Plasticity of empty major histocompatibility complex class I molecules determines peptide-selector function.

•MHC class I alleles vary in their intrinsic ability to select optimal peptides.•Ability of MHC to self-assemble is inversely correlated with dependence on tapasin.•Variation in peptide selector function correlates with the plasticity of empty MHC.•Increased plasticity of empty MHC I allows more efficient peptide selector function.•Co-ordinated domain–domain movements contribute to determine plasticity.