Blasie Cheryl A, Berg Jeremy M
Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA.
Biochemistry. 2002 Dec 17;41(50):15068-73. doi: 10.1021/bi026621h.
The thermodynamics of metal binding by the prototypical Cys(2)His(2) zinc finger peptide CP-1 has been examined through the use of isothermal titration calorimetry. In cholamine buffer at pH 7.0, the binding of zinc(II) to CP-1 shows an enthalpy change of DeltaH degrees (obs) = -33.7 +/- 0.8 kcal/mol. Between one and two protons appear to be released accompanying the metal binding process. The heat of protonation of the cholamine buffer used is quite large (-11.5 kcal/mol), indicating that a portion of the observed metal binding enthalpy is due to buffer protonation. Structure-based thermodynamic analysis including the effect of water release from zinc(II) appears to account for the entropy associated with the coupled metal binding-protein folding process semiquantitatively. The strongest driving force for the reaction is the enthalpy associated with the four bonds from zinc(II) to cysteinate and histidine residues, compared with the bonds from zinc(II) to water. The binding of cobalt(II) to CP-1 is less enthalpically driven than the binding of zinc(II) by -7.6 kcal/mol. This value is approximately equal to, but slightly larger than, the expectation based on considerations of ligand field stabilization energy.
通过等温滴定量热法研究了典型的Cys(2)His(2)锌指肽CP-1与金属结合的热力学。在pH 7.0的胆碱缓冲液中，锌(II)与CP-1的结合显示出ΔH°(obs)= -33.7±0.8 kcal/mol的焓变。在金属结合过程中，似乎有1到2个质子被释放。所用胆碱缓冲液的质子化热相当大(-11.5 kcal/mol)，这表明观察到的金属结合焓的一部分是由于缓冲液质子化。基于结构的热力学分析，包括锌(II)释放水的影响，似乎半定量地解释了与金属结合-蛋白质折叠偶联过程相关的熵。与锌(II)与水的键相比，该反应最强的驱动力是与锌(II)与半胱氨酸和组氨酸残基形成的四个键相关的焓。钴(II)与CP-1的结合在焓驱动方面比锌(II)与CP-1的结合少7.6 kcal/mol。该值大约等于但略大于基于配体场稳定能考虑的预期值。
