title: Distinctive interactions at multiple site 2 subsites by allele-specific rat and mouse ly49 determine functional binding and class I MHC specificity.
abstract: Rodent Ly49 exhibit allele-specific MHC I recognition, yet the interaction site, site 2, encompassing the area below the MHC peptide-binding groove, the alpha3 domain, and associated beta(2) microglobulin, is highly conserved among rat and mouse MHC I alleles. We previously demonstrated that allele-specific Ly49 recognition can be affected by polymorphisms specifically in the peptide anchor-binding and supertype-defining B pocket of MHC I, possibly through differential conformations assumed by solvent-exposed interaction residues when articulating with this pocket. Through mutagenesis of RT1-A1(c) and H-2D(d), we map for the first time the interaction site(s) on rat MHC I mediating rat Ly49i2 recognition and the previously unexamined Ly49G(BALB/c) interaction with H-2D(d). We demonstrate that rat Ly49i2 and mouse Ly49G use both unique and common interactions at three MHC I H chain subsites to mediate functional binding and allele-specific recognition. We find that the F subsite, formed by solvent-exposed residues below the more conserved C-terminal anchor residue-binding F pocket, acts as an anchoring location for both Ly49i2 and Ly49G, whereas these receptors exhibit distinctive reliance on solvent-exposed residues articulating with the polymorphic anchor-binding and supertype-defining pocket(s) at subsite B, as well as on interaction residues at subsite C in the MHC I alpha3 domain. Our findings, combined with previous Ly49A/H-2D(d) and Ly49C/H-2K(b) cocrystal data, suggest how allele-specific MHC I conformations and Ly49 polymorphisms may affect Ly49 placement on MHC I ligands and residue usage at site 2, thereby mediating allele-specific recognition at the highly conserved MHC I interface.
authors.affiliation: Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Kerry J
authors.initials: KJ
authors.lastname: Lavender
authors.forename: Heidi H
authors.initials: HH
authors.lastname: Chau
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Kane
mesh_terms: D000483:Alleles; D019943:Amino Acid Substitution; D000818:Animals; D000950:Antigens, Ly / Q000235:genetics* / Q000276:immunology; D001665:Binding Sites / Q000235:genetics / Q000276:immunology; D045744:Cell Line, Tumor; D006183:H-2 Antigens / Q000235:genetics* / Q000276:immunology; D037181:Lectins, C-Type / Q000235:genetics* / Q000276:immunology; D051379:Mice; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D055650:NK Cell Lectin-Like Receptor Subfamily A; D011110:Polymorphism, Genetic; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D051381:Rats; D055630:Receptors, NK Cell Lectin-Like
chemical_list: D000950:Antigens, Ly; D006183:H-2 Antigens; C527088:Klra1 protein, mouse; C527091:Klra3 protein, mouse; C527095:Klra7 protein, mouse; D037181:Lectins, C-Type; D055650:NK Cell Lectin-Like Receptor Subfamily A; D055630:Receptors, NK Cell Lectin-Like