Ojcius D M, Gapin L, Kourilsky P
Pasteur Institute, INSERM U277, Paris, France.
Biochem Biophys Res Commun. 1993 Dec 30;197(3):1216-22. doi: 10.1006/bbrc.1993.2606.
Dansylated peptides were used to characterize the dissociation of peptides from a recombinant class I major histocompatibility complex protein. Dissociation of endogenous, low-affinity peptides from the class I molecule Kd had an activation energy of 6.78 +/- 0.64 kcal/mol in the 14 to 26 degrees C temperature range, but there was a break in the Arrhenius plot between 12 and 14 degrees C. Dissociation of a dansylated, high-affinity peptide had an activation energy of 20.24 +/- 1.69 kcal/mol, and there was similarly a break in the plot. Both direct interactions between peptide and the class I heavy chain and indirect effects of the peptide affinity on the extent of light chain association with heavy chain may contribute to the difference in activation energies, while the break in the Arrhenius plots implies a temperature-dependent conformational change. Dissociation was also slowest at neutral pH, but the peptide/class I complex dissociated rapidly at pH greater than 9 and less than 5, suggesting that endocytosed class I proteins would most likely lose their bound peptides at the acidic pH of endosomes.
丹磺酰化肽被用于表征肽从重组I类主要组织相容性复合体蛋白上的解离。在14至26摄氏度温度范围内，I类分子Kd上内源性低亲和力肽的解离活化能为6.78±0.64千卡/摩尔，但在12至14摄氏度之间阿累尼乌斯图出现了一个断点。丹磺酰化高亲和力肽的解离活化能为20.24±1.69千卡/摩尔，并且在图中同样出现了一个断点。肽与I类重链之间的直接相互作用以及肽亲和力对轻链与重链缔合程度的间接影响都可能导致活化能的差异，而阿累尼乌斯图中的断点意味着存在温度依赖性的构象变化。在中性pH条件下解离也是最慢的，但肽/I类复合物在pH大于9和小于5时会迅速解离，这表明内吞的I类蛋白很可能在酸性的内体pH值下失去其结合的肽。
