title: Analysis of the structure of empty and peptide-loaded major histocompatibility complex molecules at the cell surface.
abstract: We compared the conformation of empty and peptide-loaded class I major histocompatibility complex (MHC) molecules at the cell surface. Molecular conformations were analyzed by fluorescence resonance energy transfer (FRET) between fluorescent-labeled Fab fragments bound to the alpha 2 domain of the MHC heavy chain and fluorescent-labeled Fab fragments bound to beta 2-microglobulin. No FRET was found between Fab fragments bound to empty H-2Kb, but FRET was detected when empty H-2Kb molecules were loaded with peptide. The magnitude of FRET depended on the sequence of the peptide used. The results imply that empty H-2Kb molecules are in a relatively extended conformation, and that this conformation becomes more compact when peptide is bound. These changes, which are reflected in peptide-dependent binding of monoclonal antibodies, affect the surfaces of MHC molecules available for contact with T cell receptors and hence may influence T cell-receptor recognition of MHC molecules.
authors.affiliation: Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland 21224.
authors.forename: B
authors.initials: B
authors.lastname: Catipović
authors.forename: G
authors.initials: G
authors.lastname: Talluri
authors.forename: J
authors.initials: J
authors.lastname: Oh
authors.forename: T
authors.initials: T
authors.lastname: Wei
authors.forename: X M
authors.initials: XM
authors.lastname: Su
authors.forename: T E
authors.initials: TE
authors.lastname: Johansen
authors.forename: M
authors.initials: M
authors.lastname: Edidin
authors.forename: J P
authors.initials: JP
authors.lastname: Schneck
mesh_terms: D000818:Animals; D002460:Cell Line; D000939:Epitopes; D005453:Fluorescence; D006183:H-2 Antigens / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D051379:Mice; D010047:Ovalbumin / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D001613:beta 2-Microglobulin / Q000378:metabolism
chemical_list: D000939:Epitopes; D006183:H-2 Antigens; C032876:H-2Kb protein, mouse; D010446:Peptide Fragments; D010455:Peptides; D001613:beta 2-Microglobulin; D010047:Ovalbumin