Ojcius D M, Abastado J P, Casrouge A, Mottez E, Cabanie L, Kourilsky P
Pasteur Institute, INSERM U.277, Paris, France.
J Immunol. 1993 Dec 1;151(11):6020-6.
Soluble, single-chain molecules for two MHC class I alleles, H-2Kd and H-2Kb, were used to analyze the kinetics of antigenic peptide binding to MHC. After MHC preloading with radiolabeled or fluorescent peptides, the observed rate of MHC-peptide complex dissociation increased after addition of an excess of unlabeled competitor peptide. Although exogenous peptides conforming to the allele-specific motif were required for the enhanced complex dissociation to occur, the dissociation rate of the complex was independent of exogenous peptide concentration. Similarly, the association rate of exogenous peptides was independent of concentration, reflecting the presence of low affinity peptides in the binding sites of the recombinant MHC proteins; the sequences of these endogenous peptides conform to the consensus motif for the MHC allele studied. Finally, the association rate of exogenous peptide decreased when MHC molecules were preloaded with high affinity peptides, and the binding of labeled high affinity peptide to isolated recombinant MHC was faster than the subsequent dissociation observed in the presence of competitor peptide. Taken together, these results imply that the rate of exogenous peptide binding is limited by the dissociation rate of the previously bound peptides.
用于两种I类主要组织相容性复合体（MHC）等位基因H-2Kd和H-2Kb的可溶性单链分子，被用于分析抗原肽与MHC结合的动力学。在用放射性标记或荧光肽预加载MHC后，加入过量未标记的竞争肽后，观察到的MHC-肽复合物解离速率增加。尽管增强的复合物解离需要符合等位基因特异性基序的外源肽，但复合物的解离速率与外源肽浓度无关。同样，外源肽的结合速率也与浓度无关，这反映了重组MHC蛋白结合位点中存在低亲和力肽；这些内源性肽的序列符合所研究MHC等位基因的共有基序。最后，当MHC分子用高亲和力肽预加载时，外源肽的结合速率降低，并且标记的高亲和力肽与分离的重组MHC的结合比在存在竞争肽时观察到的随后解离更快。综上所述，这些结果表明外源肽结合速率受先前结合肽的解离速率限制。
