期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1992
卷号：89
期号：6
页码：2242-2246
DOI：10.1073/pnas.89.6.2242
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：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.
