title: Tmp21, a novel MHC-I interacting protein, preferentially binds to Β2-microglobulin-free MHC-I heavy chains.
abstract: MHC-I molecules play a critical role in immune surveillance against viruses by presenting peptides to cytotoxic T lymphocytes. Although the mechanisms by which MHC-I molecules assemble and acquire peptides in the ER are well characterized, how MHC-I molecules traffic to the cell surface remains poorly understood. To identify novel proteins that regulate the intracellular transport of MHC-I molecules, MHC-I-interacting proteins were isolated by affinity purification, and their identity was determined by mass spectrometry. Among the identified MHC-I-associated proteins was Tmp21, the human ortholog of yeast Emp24p, which mediates the ER-Golgi trafficking of a subset of proteins. Here, we show that Tmp21 binds to human classical and non-classical MHC-I molecules. The Tmp21-MHC-I complex lacks Β(2)-microglobulin, and the number of the complexes is increased when free MHC-I heavy chains are more abundant. Taken together, these results suggest that Tmp21 is a novel protein that preferentially binds to Β(2)-microglobulin-free MHC-I heavy chains.
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea. junys@gist.ac.kr
authors.forename: Youngsoo
authors.initials: Y
authors.lastname: Jun
authors.forename: Kwangseog
authors.initials: K
authors.lastname: Ahn
mesh_terms: D015395:Histocompatibility Antigens Class I / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008285:Major Histocompatibility Complex; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins; D011485:Protein Binding; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D001613:beta 2-Microglobulin / Q000378:metabolism*
chemical_list: D015395:Histocompatibility Antigens Class I; D008565:Membrane Proteins; D029543:Nucleocytoplasmic Transport Proteins; D034741:RNA, Small Interfering; C484395:TMED10 protein, human; D001613:beta 2-Microglobulin