Predicted to enable MHC class II protein complex binding activity and protein homodimerization activity. Involved in learning or memory; modulation of age-related behavioral decline; and negative regulation of cell differentiation. Acts upstream of or within several processes, including antigen processing and presentation of exogenous protein antigen via MHC class Ib, TAP-dependent; cellular response to iron(III) ion; and protein refolding. Located in external side of plasma membrane. Is expressed in several structures, including central nervous system; early conceptus; genitourinary system; hemolymphoid system gland; and retina. Used to study hemochromatosis and type 1 diabetes mellitus. Human ortholog(s) of this gene implicated in arthritis; familial visceral amyloidosis; immunodeficiency 43; and inflammatory bowel disease. Orthologous to human B2M (beta-2-microglobulin). [provided by Alliance of Genome Resources, Apr 2022]