Dragan A I, Khrapunov S N, Berdyshev G D
Mol Biol (Mosk). 1985 Sep-Oct;19(5):1259-68.
Dynamic equilibrium analysis of the (H2A-H2B-H3-H4)2 histone octamer with lower oligomers was performed in 2 M NaCl. Calculated data on the relative content of histone oligomers upon changing protein concentration in solution are given. The red shift of lambda max for histone tyrosine fluorescence spectra is shown to be due to hydrogen bond formation by tyrosyl OH-groups. Analysis of free energy changes of histone oligomers upon association (delta G = -17,37 +/- 0,14 kcal/mole) as well as the effect of urea on histone octamer dissociation made it possible to conclude that virtually all tyrosyls in octamer form hydrogen bonds. Intermolecular hydrogen bonds formed by tyrosyls contribute substantially to octamer stabilization. The (H2A-H2B) dimer positive cooperativity in association with the (H3-H4)2 tetramer was found. This cooperativity is caused by interaction between association sites with a two order increase in an apparent constant of dimers with tetramer association. The histone octamer was determined to be of asymmetric structure due to unequivolency of the two binding sites for the (H2A-H2B) dimers.
在2M氯化钠溶液中对(H2A - H2B - H3 - H4)2组蛋白八聚体与低聚物进行了动态平衡分析。给出了溶液中蛋白质浓度变化时组蛋白低聚物相对含量的计算数据。组蛋白酪氨酸荧光光谱的最大波长红移被证明是由于酪氨酸羟基形成氢键所致。对组蛋白低聚物缔合时自由能变化（ΔG = -17.37 ± 0.14千卡/摩尔）以及尿素对组蛋白八聚体解离的影响进行分析后得出结论，八聚体中几乎所有酪氨酸都形成了氢键。酪氨酸形成的分子间氢键对八聚体的稳定起了重要作用。发现了(H2A - H2B)二聚体与(H3 - H4)2四聚体缔合时的正协同性。这种协同性是由缔合位点之间的相互作用引起的，二聚体与四聚体缔合的表观常数增加了两个数量级。由于(H2A - H2B)二聚体的两个结合位点不等价，确定组蛋白八聚体具有不对称结构。
