Pedersen L O, Hansen A S, Olsen A C, Gerwien J, Nissen M H, Buus S
Institute for Medical Microbiology and Immunology, University of Copenhagen, Denmark.
Scand J Immunol. 1994 Jan;39(1):64-72. doi: 10.1111/j.1365-3083.1994.tb03341.x.
The function of MHC class-I molecules is to sample peptides from the intracellular environment and present them to CD8+ cytotoxic T lymphocytes. To understand the molecular details of the assembly (and disassembly) of peptide-beta 2m-class-I complexes a biochemical peptide-class-I binding assay has been generated recently and this paper reports on a similar assay for the interaction between beta 2m and class I. As a model system human beta 2m binding to mouse class I was used. The assay is strictly biochemical using purified reagents which interact in solution and complex formation is determined by size separation. It is specific and highly sensitive. The observed affinity of the interaction, KD, is close to 0.4 nM. The rate of association at 37 degrees C is very fast (the ka is around 5 x 10(4)/M/s) whereas the dissociation is slow (the kd is around 8 x 10(-6)/s); the ratio of dissociation to association yields a calculated KD close to the observed value. At 37 degrees C almost all of the purified class I participates in binding of the exogenously offered beta 2m showing that a considerable exchange of the endogenous beta 2m occurs. Finally, it was demonstrated that exogenous beta 2m enhances binding to MHC class-I of short perfectly-matching peptides as well as longer peptides.
MHC I类分子的功能是从细胞内环境中筛选肽段，并将其呈递给CD8 + 细胞毒性T淋巴细胞。为了了解肽-β2微球蛋白-I类复合物组装（和解组装）的分子细节，最近建立了一种生化肽-I类结合试验，本文报道了一种类似的β2微球蛋白与I类相互作用的试验。使用人β2微球蛋白与小鼠I类的结合作为模型系统。该试验完全是生化试验，使用在溶液中相互作用的纯化试剂，通过大小分离来确定复合物的形成。它具有特异性且高度灵敏。观察到的相互作用亲和力KD接近0.4 nM。37℃时的缔合速率非常快（ka约为5×10⁴/M/s），而解离速率较慢（kd约为8×10⁻⁶/s）；解离与缔合的比率得出的计算KD接近观察值。在37℃时，几乎所有纯化的I类分子都参与了外源提供的β2微球蛋白的结合，这表明内源性β2微球蛋白发生了相当程度的交换。最后，证明外源β2微球蛋白增强了短的完全匹配肽以及较长肽与MHC I类分子的结合。
