Energetics of folding and DNA binding of the MAT alpha 2 homeodomain.
Energetics of folding and DNA binding of the MAT alpha 2 homeodomain.
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MAT α 2 同源域的折叠和 DNA 结合能量。
DOI：
10.1021/bi962206b
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Privalov,PL
中科院分区：
文献类型：
--
作者：
Carra,JH;Privalov,PL
同源结构域是一类与DNA结合的蛋白结构域，在真核生物的遗传调控中发挥着重要作用。我们已经表征了酵母MATα2同源域的折叠和序列特异性结合的热力学。用差示扫描量热法和等温滴定量热法测量了这些过程的热焓、热容和吉布斯自由能的变化。在生理温度下，蛋白质与−的相互作用是由热能驱动的。将蛋白质−复合体在不同盐浓度下熔融过程的差示扫描量热数据分解为吸热组分，得到结合热变化和解离常数。比较游离态和结合态蛋白质的圆二色谱，发现与脱氧核糖核酸结合后形成了额外的α螺旋结构。我们认为，在所用的条件下，螺旋3的后半部分，即识别螺旋，在游离蛋白中基本上是展开的，就像对其他同源结构域的观察一样[Tsao，D.H.H.，等人。(1994年)生物化学33,15053−15060；考克斯，M.等。(1995)J.Biomol.核磁共振5，23−32]。蛋白质结构的形成是由DNA结合诱导的，因此为结合而测量的能量包括由于折叠而产生的成分。
Homeodomains are a class of DNA-binding protein domains which play an important role in genetic regulation in eukaryotes. We have characterized the thermodynamics of folding and sequence-specific association with DNA of the MATα2 homeodomain of yeast. Using differential scanning and isothermal titration calorimetry, we measured the enthalpy, heat capacity, and Gibbs free energy changes of these processes. The protein−DNA interaction is enthalpically driven at physiological temperatures. DSC data on the process of melting the protein−DNA complex at different salt concentrations were dissected into its endothermic components, yielding the enthalpy change and dissociation constant of binding. A comparison of the circular dichroism spectra of the free and DNA-bound protein species revealed the formation of additional α-helical structure upon binding to DNA. We propose that the latter half of helix 3, the recognition helix, is substantially unfolded in the free protein under the conditions used, as has been observed with other homeodomains [Tsao, D. H. H., et al. (1994)Biochemistry 33, 15053−15060; Cox, M., et al. (1995)J.Biomol. NMR 5, 23−32]. Formation of protein structure is induced by DNA binding, and the energies measured for association therefore include a component due to folding.