title: Structure of a classical MHC class I molecule that binds "non-classical" ligands.
abstract: Chicken YF1 genes share a close sequence relationship with classical MHC class I loci but map outside of the core MHC region. To obtain insights into their function, we determined the structure of the YF1*7.1/β(2)-microgloblin complex by X-ray crystallography at 1.3 Å resolution. It exhibits the architecture typical of classical MHC class I molecules but possesses a hydrophobic binding groove that contains a non-peptidic ligand. This finding prompted us to reconstitute YF1*7.1 also with various self-lipids. Seven additional YF1*7.1 structures were solved, but only polyethyleneglycol molecules could be modeled into the electron density within the binding groove. However, an assessment of YF1*7.1 by native isoelectric focusing indicated that the molecules were also able to bind nonself-lipids. The ability of YF1*7.1 to interact with hydrophobic ligands is unprecedented among classical MHC class I proteins and might aid the chicken immune system to recognize a diverse ligand repertoire with a minimal number of MHC class I molecules.
authors.affiliation: Institut für Immungenetik, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, Freie Universität Berlin, Berlin, Germany.
authors.forename: Chee Seng
authors.initials: CS
authors.lastname: Hee
authors.forename: Song
authors.initials: S
authors.lastname: Gao
authors.forename: Bernhard
authors.initials: B
authors.lastname: Loll
authors.forename: Marcia M
authors.initials: MM
authors.lastname: Miller
authors.forename: Barbara
authors.initials: B
authors.lastname: Uchanska-Ziegler
authors.forename: Oliver
authors.initials: O
authors.lastname: Daumke
authors.forename: Andreas
authors.initials: A
authors.lastname: Ziegler
mesh_terms: D000818:Animals; D002645:Chickens / Q000276:immunology / Q000502:physiology*; D018360:Crystallography, X-Ray; D005805:Genes, MHC Class I; D015395:Histocompatibility Antigens Class I / Q000737:chemistry* / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D007525:Isoelectric Focusing; D001613:beta 2-Microglobulin / Q000737:chemistry / Q000378:metabolism
chemical_list: D015395:Histocompatibility Antigens Class I; D001613:beta 2-Microglobulin