Binds and activates the KLRK1/NKG2D receptor, mediating natural killer cell cytotoxicity. Interacts with KLRK1/NKG2D (PubMed:11777960). Does not bind to beta2-microglobulin (PubMed:12782710). (Microbial infection) In CMV-infected cells, interacts with the viral glycoprotein UL16; this interaction causes ULBP1 retention in the endoplasmic reticulum and cis-Golgi and prevents binding to and activation of KLRK1/NKG2D, providing CMV with an immune evasion mechanism. In CMV-infected fibroblasts, detected in the endoplasmic reticulum/cis-Golgi. Expressed in T-cells, B-cells, erythroleukemia cell lines and in a wide range of tissues including heart, brain, lung, liver, testis, lymph node, thymus, tonsil and bone marrow. Also found in fetal heart, brain, lung and liver. UL16-binding proteins (ULBPs) are unusual members of the extended MHC class I superfamily. They do not contain the alpha 3 domain and lack a transmembrane domain. Belongs to the MHC class I family.