Maenaka K, van der Merwe P A, Stuart D I, Jones E Y, Sondermann P
Structural Biology Center, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan.
J Biol Chem. 2001 Nov 30;276(48):44898-904. doi: 10.1074/jbc.M106819200. Epub 2001 Sep 5.
Fcgamma receptors (FcgammaRs) are expressed on all immunologically active cells. They bind the Fc portion of IgG, thereby triggering a range of immunological functions. We have used surface plasmon resonance to analyze the kinetic and thermodynamic properties of the interactions between the ectodomains of human low affinity FcgammaRs (FcgammaRIIa, FcgammaRIIb, and FcgammaRIIIb-NA2) and IgG1 or the Fc fragment of IgG1. All three receptors bind Fc or IgG with similarly low affinities (K(D) approximately 0.6-2.5 microm) and fast kinetics, suggesting that FcgammaR-mediated recognition of aggregated IgG and IgG-coated particles or cells is mechanistically similar to cell-cell recognition. Interestingly, the Fc receptors exhibit distinct thermodynamic properties. Whereas the binding of the FcgammaRIIa and FcgammaRIIb to Fc is driven by favorable entropic and enthalpic changes, the binding of FcgammaRIII is characterized by highly unfavorable entropic changes. Although the structural bases for these differences remain to be determined, they suggest that the molecular events coupled to the binding differ among the low affinity FcgammaRs.
Fcγ受体（FcγRs）在所有免疫活性细胞上均有表达。它们与IgG的Fc部分结合，从而触发一系列免疫功能。我们利用表面等离子体共振分析了人低亲和力Fcγ受体（FcγRIIa、FcγRIIb和FcγRIIIb-NA2）胞外域与IgG1或IgG1的Fc片段之间相互作用的动力学和热力学特性。所有这三种受体与Fc或IgG结合的亲和力相似且较低（解离常数K(D)约为0.6 - 2.5微摩尔），动力学速度较快，这表明FcγR介导的对聚集IgG以及IgG包被颗粒或细胞的识别在机制上类似于细胞间识别。有趣的是，Fc受体表现出不同的热力学特性。FcγRIIa和FcγRIIb与Fc的结合由有利的熵变和焓变驱动，而FcγRIII与Fc的结合则以高度不利的熵变为特征。尽管这些差异的结构基础仍有待确定，但它们表明与结合相关的分子事件在低亲和力Fcγ受体之间存在差异。
