title: Peptide binding to active class II MHC protein on the cell surface.
abstract: Solution studies have demonstrated the existence of two functionally distinct isomers of empty class II MHC: an active isomer that binds peptide and an inactive isomer that does not. Empty MHC molecules on the surface of APCs can load antigenic peptides directly from the extracellular medium, facilitating the generation of a diverse peptide repertoire for T cell presentation. In this report, we examine I-Ek on the surface of Chinese hamster ovary cells with respect to the active and inactive isomers. As in the case of purified soluble active I-Ek, active I-Ek on the cell surface is unstable, decaying to the inactive form in approximately 14 min. Evidence is presented suggesting that at steady state <1% of the total cell surface I-Ek is active and that a significant fraction of these active molecules originates from intracellular pools as well as reactivation of inactive cell surface I-EK.
authors.affiliation: Department of Chemistry, Stanford University, Stanford, CA 94305, USA.
authors.forename: J F
authors.initials: JF
authors.lastname: Vacchino
authors.forename: H M
authors.initials: HM
authors.lastname: McConnell
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation / Q000187:drug effects; D019921:Biotinylation; D020126:Brefeldin A / Q000494:pharmacology; D016466:CHO Cells; D002462:Cell Membrane / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D002738:Chloroquine / Q000494:pharmacology; D006224:Cricetinae; D003574:Cytochrome c Group / Q000276:immunology / Q000378:metabolism; D000949:Histocompatibility Antigens Class II / Q000276:immunology / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D009036:Moths / Q000201:enzymology / Q000276:immunology; D010446:Peptide Fragments / Q000276:immunology* / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects / Q000276:immunology; D021381:Protein Transport / Q000187:drug effects / Q000276:immunology; D019810:Sodium Azide / Q000494:pharmacology; D012995:Solubility; D014162:Transfection
chemical_list: D003574:Cytochrome c Group; D000949:Histocompatibility Antigens Class II; C024138:I-E-antigen; D010446:Peptide Fragments; D020126:Brefeldin A; D002738:Chloroquine; D019810:Sodium Azide