title: Peptides control the gain and loss of allele specificity by mutated MHC class I molecules.
abstract: To analyze the molecular basis of MHC class I allele-restricted peptide recognition, a set of eight Ld/Lq mutants was constructed and tested for peptide recognition by allele-restricted and peptide-specific CTL. The MHC molecules H-2Ld and H-2Lq differ at six amino acid positions (95, 97, 107, 116, 155, 157) located within the alpha 2 domain of the molecule. Both molecules present the lymphocytic choriomeningitis virus (LCMV) nucleoprotein-derived peptide RPQASGVYM and the murine cytomegalovirus (MCMV) pp89-derived peptide YPHFMPTNL to the respective virus-specific CD8+ CTL is a strictly allele-restricted fashion. All mutated MHC class I molecules did still bind the LCMV peptide and seven of eight mutants retained MCMV peptide binding. The exchange Arg-->Trp at position 97 of Lq in pocket C of the peptide binding groove prevented binding of the MCMV ligand and this loss was compensated by the additional exchange of Ile-->Leu in position 95 (pocket F). Within the Lq molecule, single mutations at either position 97 on the floor of the groove or position 155 of the wall sufficed for a gain of LCMV peptide recognition by Ld-restricted CTL. Altogether, six of eight mutants resulted in a gain of recognition by CTL specific for the other allele. Thus, six of the eight mutants lost MHC-restricted recognition and were accepted by both Ld- as well as Lq-restricted CTL when presenting the LCMV peptide. Only one case of simultaneous recognition of the MCMV peptide by both Ld- as well as Lq-restricted CTL was noted. In other mutations, a gain of recognition by Ld-restricted CTL was associated with a loss of recognition of Lq-restricted CTL. Analysis of extracted MCMV peptide from mutant molecules excluded quantitative differences in presented MCMV peptide as a reason for the lack of CTL recognition. Altogether, the results show that, rather than aminoacids at certain residue positions, individual peptides govern MHC allele specificity of CTL recognition.
authors.affiliation: Department of Virology, University of Heidelberg, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Hengel
authors.forename: K
authors.initials: K
authors.lastname: Burke
authors.forename: D
authors.initials: D
authors.lastname: Kyburz
authors.forename: R M
authors.initials: RM
authors.lastname: Zinkernagel
authors.forename: U H
authors.initials: UH
authors.lastname: Koszinowski
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation / Q000276:immunology; D000956:Antigens, Viral / Q000276:immunology*; D003601:Cytotoxicity Tests, Immunologic; D006183:H-2 Antigens / Q000235:genetics*; D008217:Lymphocytic choriomeningitis virus / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008815:Mice, Inbred Strains; D008969:Molecular Sequence Data; D018146:Muromegalovirus / Q000276:immunology; D016297:Mutagenesis, Site-Directed; D010455:Peptides / Q000502:physiology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology
chemical_list: D000956:Antigens, Viral; D006183:H-2 Antigens; D010455:Peptides