Thermodynamic Effect of Complementary Hydrogen Bond Base Pairing on Aromatic Stacking Interaction in the Guanine-X-Trp Complex (X=Adenine, Guanine, Cytosine, Thymin.
作者:Mariko TARUI、Noriko NOMOTO、Yoko HASEGAWA、Katsuhiko MINOURA、Mitsunobu DOI、Toshimasa ISHIDA
DOI:10.1248/cpb.44.1998
日期:——
Four kinds of X-Trp (X=adenine, guanine, cytosine, thymine) were synthesized as model compounds to investigate the effect of complementary hydrogen bond base pairing on the stacking interaction of Trp with nucleic acid base. Association constants (Ka) of these compounds with two guanine derivatives (9-ethylguanine and 9-ethyl-7-methylguanine) were determined by Eadie-Hofstee plots of 1H-NMR titration experiments, and the thermodynamic parameters (ΔH, ΔS and ΔG) for the respective complexes were obtained by van't Hoff analyses based on the temperature dependence of the Ka values. The complexes were characterized by enthalpy/entropy compensations, where the interaction of cytosine-Trp with guanine derivatives was largely enthalpy-driven, accompanied by a small entropy component, whereas those of remaining complexes were all associated with a large increase in entropy, accompanied by a small positive enthalpy component. The present insight on the binding of X-Trp with a guanine base provides a thermodynamic basis for the importance of cooperative hydrogen bond pairing and aromatic stacking interactions in the specific recognition of a nucleic acid base pair by protein.
合成了四种X-Trp(X=腺嘌呤、鸟嘌呤、胞嘧啶、胸腺嘧啶)作为模型化合物,以研究互补氢键碱基配对对色氨酸与核酸碱基堆叠相互作用的影响。通过Eadie-Hofstee图分析1H-NMR滴定实验,确定了这些化合物与两种鸟嘌呤衍生物(9-乙基鸟嘌呤和9-乙基-7-甲基鸟嘌呤)的结合常数(Ka),并通过van't Hoff分析基于Ka值的温度依赖性得到了相应复合物的热力学参数(ΔH,ΔS和ΔG)。这些复合物的特征表现为焓/熵补偿,其中胞嘧啶-色氨酸与鸟嘌呤衍生物的相互作用主要由焓驱动,同时伴随较小的熵成分,而其余复合物则均与熵的大幅增加相关,伴随较小的正焓成分。本研究对X-Trp与鸟嘌呤碱基结合的洞察,为氢键配对的协同效应和芳香堆叠相互作用在蛋白质特异性识别核酸碱基对中的重要性提供了热力学依据。