title: Dissection of the interaction of the human cytomegalovirus-derived US2 protein with major histocompatibility complex class I molecules: prominent role of a single arginine residue in human leukocyte antigen-A2.
abstract: Human cytomegalovirus encodes several proteins that interfere with expression of major histocompatibility complex (MHC) class I molecules on the surface of infected cells. The unique short protein 2 (US2) binds to many MHC class I allomorphs in the endoplasmic reticulum, preventing cell surface expression of the class I molecule in question. The molecular interactions underlying US2 binding to MHC class I molecules and its allele specificity have not been fully clarified. In the present study, we first compared the sequences and the structures of US2 retained versus non-retained human leukocyte antigen (HLA) class I allomorphs to identify MHC residues of potential importance for US2 binding. On the basis of this analysis, 18 individual HLA-A2 mutants were generated and the ability of full-length US2 to bind wild-type and mutated HLA-A2 complexes was assessed. We demonstrate that Arg181 plays a critical role in US2-mediated inhibition of HLA-A2 cell surface expression. The structural comparison of all known crystal structures of HLA-A2 either alone, or in complex with T cell receptor or the CD8 co-receptor, indicates that binding of US2 to HLA-A2 results in a unique, large conformational change of the side chain of Arg181. However, although the presence of Arg181 seems to be a prerequisite for US2 binding to HLA-A2, it is not sufficient for binding to all MHC class I alleles.
authors.affiliation: Center for Infectious Medicine, Department of Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, S-141 86 Stockholm, Sweden.
authors.forename: Claudia
authors.initials: C
authors.lastname: Thilo
authors.forename: Peter
authors.initials: P
authors.lastname: Berglund
authors.forename: Steven E
authors.initials: SE
authors.lastname: Applequist
authors.forename: Jonathan W
authors.initials: JW
authors.lastname: Yewdell
authors.forename: Hans-Gustaf
authors.initials: HG
authors.lastname: Ljunggren
authors.forename: Adnane
authors.initials: A
authors.lastname: Achour
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D001120:Arginine / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D002460:Cell Line; D016384:Consensus Sequence; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate; D005456:Fluorescent Dyes; D015789:HLA-A2 Antigen / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015395:Histocompatibility Antigens Class I / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006860:Hydrogen Bonding; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D019076:Transgenes; D014615:Vaccinia; D014759:Viral Envelope Proteins / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000911:Antibodies, Monoclonal; D005456:Fluorescent Dyes; D015789:HLA-A2 Antigen; D015395:Histocompatibility Antigens Class I; C118670:US2 protein, Varicellovirus; D014759:Viral Envelope Proteins; C510375:Wdr83 protein, rat; D001120:Arginine; D016650:Fluorescein-5-isothiocyanate