Solution binding of an antigenic peptide to a major histocompatibility complex class I molecule and the role of beta 2-microglobulin.
The major histocompatibility complex-encoded class I molecule, a noncovalent dimer of a polymorphic 45-kDa heavy chain and a nonpolymorphic 12-kDa beta 2-microglobulin (beta 2m) light chain, binds peptide antigen prior to its interaction with T-cell antigen receptors. We report here that the binding in aqueous solution at 37 degrees C of a soluble purified murine major histocompatibility complex class I protein, H-2Lds (a soluble analogue of H-2Ld consisting of the alpha 1 and alpha 2 domains of H-2Ld, the alpha 3 domain and the C terminus of Q10b), to an antigenic peptide is controlled by the light-chain subunit beta 2m. Analysis of the equilibrium binding data favors a model in which two classes of peptide binding sites exist, the high-affinity class having an equilibrium constant for dissociation, KH, of 3.7 x 10(-7) M and accounting for 12% of the theoretically available sites. Studies of binding in the presence of excess beta 2m indicate that this increases the concentration of available high-affinity sites. These data are consistent with a ternary model in which high-affinity sites are generated by the interaction of beta 2m with the peptide-binding class I heavy chain.
Boyd
L F
LF
Molecular Biology Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892.
Kozlowski
S
S
Margulies
D H
DH
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D001667:Binding, Competitive; D002846:Chromatography, Affinity; D006183:H-2 Antigens / Q000378:metabolism*; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D007739:L Cells; D046911:Macromolecular Substances; D051379:Mice; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis / Q000378:metabolism*; D014162:Transfection; D001613:beta 2-Microglobulin / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D006183:H-2 Antigens; D015395:Histocompatibility Antigens Class I; D046911:Macromolecular Substances; D009842:Oligopeptides; D001613:beta 2-Microglobulin