title: MHC class II function preserved by low-affinity peptide interactions preceding stable binding.
abstract: Major histocompatibility complex class II molecules and their peptide ligands show unusual interaction kinetics, with slow association and dissociation rates that yield an apparent equilibrium constant of approximately 10(-6)-10(-8) M (refs 1-5). However, there is evidence for a specific, rapidly formed, short-lived complex. The altered migration on SDS-polyacrylamide gel electrophoresis of class II molecules upon stable peptide binding has led to the hypothesis that the two kinetically distinguishable types of class II-peptide complexes correspond to different structures. In accord with this model, we demonstrate here that insect cell-derived HLA-DR1 class II molecules show fast, almost stoichiometric occupancy with rapidly dissociating peptide while remaining sensitive to SDS-induced chain dissociation. The same DR1 molecules slowly and quantitatively form long-lived complexes resistant to SDS-induced denaturation. Surprisingly, low-affinity interaction with peptide protects class II from denaturation at physiological temperature, a finding that has implications for understanding the role of invariant chain in the intracellular behaviour of class II molecules.
authors.affiliation: Laboratory of Immunology, NIAID, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: S
authors.initials: S
authors.lastname: Sadegh-Nasseri
authors.forename: L J
authors.initials: LJ
authors.lastname: Stern
authors.forename: D C
authors.initials: DC
authors.lastname: Wiley
authors.forename: R N
authors.initials: RN
authors.lastname: Germain
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D015798:HLA-DR1 Antigen / Q000737:chemistry / Q000378:metabolism*; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D006389:Hemagglutinins, Viral / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D009036:Moths; D010446:Peptide Fragments / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology; D011485:Protein Binding
chemical_list: D015798:HLA-DR1 Antigen; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D006389:Hemagglutinins, Viral; D010446:Peptide Fragments; D011480:Protease Inhibitors; C086595:influenza hemagglutinin (306-318)