Torigoe H, Nakayama T, Imazato M, Shimada I, Arata Y, Sarai A
Tsukuba Life Science Center, Institute of Physical and Chemical Research (RIKEN), Tsukuba, Japan.
J Biol Chem. 1995 Sep 22;270(38):22218-22. doi: 10.1074/jbc.270.38.22218.
To understand the mechanism of affinity maturation, we examined the antigen-antibody interactions between 4-hydroxy-3-nitrophenylacetyl (NP) caproic acid and the Fab fragments of three anti-NP antibodies, N1G9, 3B44, and 3B62, by isothermal titration calorimetry. The analyses have revealed that all of these interactions are mainly driven by negative changes in enthalpy. The enthalpy changes decreased linearly with temperature in the range of 25-45 degrees C, producing negative changes in heat capacity. On the basis of the dependence of binding constants on the sodium chloride concentration, we have shown that, during the affinity maturation of the anti-NP antibody, the electrostatic effect does not significantly contribute to the increase in the binding affinity. We have found that, as the logarithm of the binding constants increases during the affinity maturation of the anti-NP antibody, the magnitudes of the corresponding enthalpy, heat capacity, and unitary entropy changes increase almost linearly. On the basis of this correlation, we have concluded that, during the affinity maturation of the anti-NP antibody, a better surface complementarity is attained in the specific complex in order to obtain a higher binding affinity.
为了解亲和力成熟的机制，我们通过等温滴定量热法研究了4-羟基-3-硝基苯乙酰（NP）己酸与三种抗NP抗体N1G9、3B44和3B62的Fab片段之间的抗原-抗体相互作用。分析表明，所有这些相互作用主要由焓的负变化驱动。在25-45摄氏度范围内，焓变随温度呈线性下降，产生了热容的负变化。基于结合常数对氯化钠浓度的依赖性，我们表明，在抗NP抗体的亲和力成熟过程中，静电效应并未显著促进结合亲和力的增加。我们发现，在抗NP抗体的亲和力成熟过程中，随着结合常数对数的增加，相应的焓变、热容变和单位熵变的幅度几乎呈线性增加。基于这种相关性，我们得出结论，在抗NP抗体的亲和力成熟过程中，特异性复合物中实现了更好的表面互补性，以获得更高的结合亲和力。
