DNA binding of a non-sequence-specific HMG-D protein is entropy driven with a substantial non-electrostatic contribution
DNA binding of a non-sequence-specific HMG-D protein is entropy driven with a substantial non-electrostatic contribution
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DOI：
10.1016/s0022-2836(03)00785-x
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发表时间：
2003-08-22
影响因子：
5.6
通讯作者：
Privalov, PL
中科院分区：
文献类型：
--
作者：
Dragan, AI;Klass, J;Privalov, PL
使用扫描和滴定微量热法、分光偏振法、荧光各向异性和 FRET 技术，在不同温度下研究了两种形式的果蝇 HMGD 蛋白（有或没有高碱性 26 残基 C 末端尾部（D100 和 D74））的热性质，以及它们与线性 DNA 双链体的非序列特异性相互作用的热力学。 温度和盐浓度。结果表明，D100 的 C 末端尾部在所有温度下都会展开，而球状部分的状态以相当复杂的方式取决于温度，仅在接近 0°C 的温度下完全折叠，并在低于总变性变化的温度下展开并显着吸热。 D100 的缔合常数和吉布斯结合能远大于 D74，但它们的缔合焓相似且大且为正，即 DNA 结合是完全熵驱动的过程。缔合的正熵是由于形成蛋白质/DNA复合物时抗衡离子的释放和脱水造成的。离子强度变化表明，静电相互作用在这种非序列特异性蛋白质球状部分的 DNA 结合中发挥着重要但非排他性的作用，而 D100 带正电的 C 末端尾部的结合几乎完全是静电起源的。这种与 DNA 磷酸基团负电荷的相互作用显着增强了 DNA 弯曲。这些 HMG 盒与 DNA 的非序列特异性关联的一个重要特征是，结合焓显着高于 Sox-5 的 HMG 盒的序列特异性关联。尽管事实上这些蛋白质使 DNA 双链体弯曲到相似的程度。这种差异表明，HMG-D/DNA 界面上非极性基团的脱水焓并未完全被这些基团之间范德华相互作用的能量所补偿，即界面处的堆积密度必须低于序列特异性 Sox-5 HMG 盒的堆积密度。 (C) 2003 Elsevier Ltd. 保留所有权利。
The thermal properties of two forms of the Drosophila melanogaster HMGD protein, with and without its highly basic 26 residue C-terminal tail (D100 and D74) and the thermodynamics of their non-sequence-specific interaction with linear DNA duplexes were studied using scanning and titration microcalorimetry, spectropolarimetry, fluorescence anisotropy and FRET techniques at different temperatures and salt concentrations. It was shown that the C-terminal tail of D100 is unfolded at all temperatures, whilst the state of the globular part depends on temperature in a rather complex way, being completely folded only at temperatures close to 0degreesC and unfolding with significant heat absorption at temperatures below those of the gross denaturational changes. The association constant and thus Gibbs energy of binding for D100 is much greater than for D74 but the enthalpies of their association are similar and are large and positive, i.e. DNA binding is a completely entropy-driven process. The positive entropy of association is due to release of counterions and dehydration upon forming the protein/DNA complex. Ionic strength variation showed that electrostatic interactions play an important but not exclusive role in the DNA binding of the globular part of this non-sequence-specific protein, whilst binding of the positively charged C-terminal tail of D100 is almost completely electrostatic in origin. This interaction with the negative charges of the DNA phosphate groups significantly enhances the DNA bending. An important feature of the non-sequence-specific association of these HMG boxes with DNA is that the binding enthalpy is significantly more positive than for the sequence-specific association of the HMG box from Sox-5. despite the fact that these proteins bend the DNA duplex to a similar extent. This difference shows that the enthalpy of dehydration of apolar groups at the HMG-D/DNA interface is not fully compensated by the energy of van der Waals interactions between these groups, i.e. the packing density at the interface must be lower than for the sequence-specific Sox-5 HMG box. (C) 2003 Elsevier Ltd. All rights reserved.