The energetics of HMG box interactions with DNA. Thermodynamic description of the box from mouse Sox-5
The energetics of HMG box interactions with DNA. Thermodynamic description of the box from mouse Sox-5
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DOI：
10.1006/jmbi.1998.1895
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发表时间：
1998-08-28
影响因子：
5.6
通讯作者：
Privalov, PL
中科院分区：
文献类型：
--
作者：
Crane-Robinson, C;Read, CM;Privalov, PL
用量热法研究了小鼠SOX-5 DNA结合蛋白HMG盒的结构能量学。研究发现，尽管这种盒子的尺寸很小(分子质量约为10 kDa)，但它并不是一个单一的合作单元，而且在加热时，盒子可逆地展开为两个不同的阶段。第一个转变(t(T)类似于34摄氏度)约占总热焓的40%，第二个转变(t(T)类似于46摄氏度)涉及其余部分。这两个转变都伴随着显著的热容增加，表明它们与具有非极性核的两个子域的展开有关。根据热容、椭圆度、荧光和核磁共振判据，该HMG盒仅在5℃以下处于完全紧凑的自然状态。HMG盒由两个近似正交的翼组成：小翼包括螺旋3及其相关的反平行N末端链，而主翼由螺旋I和II组成。对不同温度下获得的盒的荧光和核磁共振光谱分析表明，下熔化转变可归属于小翼，上部转变可归属于主翼。在生理条件下(37摄氏度)，小翼相当程度地展开，而大翼基本上完全折叠。因此，体内的DNA结合涉及小翅膀的重新折叠。(C)1998年学术出版社。
The structural energetics of the HMG box from the DNA-binding protein mouse Sox-5 were examined calorimetrically. It was found that this box, notwithstanding its small size (molecular mass about 10 kDa), does not behave as a single cooperative unit and, on heating, the box reversibly unfolds In two separate stages. The first transition (t(t) similar to 34 degrees C) involves about 40% of the total enthalpy and the second (t(t) similar to 46 degrees C) the remainder. Both transitions proceed with significant heat capacity increment, showing that they are associated with the unfolding, of two sub-domains having non-polar cores. According to heat capacity, ellipticity, fluorescence and NMR criteria, this HMG box is in a fully compact native state only below 5 degrees C. HMG boxes consist of two approximately orthogonal wings: the minor wing comprises helix 3 and its associated antiparallel N-terminal strand, whilst the major wing is composed of helices I and II. Analysis of the fluorescence and NMR spectra for this;box obtained at different temperatures shows that the lower melting transition can be assigned to the minor wing and the upper transition to the major wing. Under physiological conditions (37 degrees C), the minor wing is considerably unfolded, whilst the major wing is essentially fully folded. DNA binding in vivo therefore involves refolding of the minor wing. (C) 1998 Academic Press.