溶液中离子诱导的染色质结构转变
Structural transition in chromatin induced by ions in solution.
作者信息
Li H J, Hu A W, Maciewicz R A, Cohen P, Santella R M, Chang C
出版信息
Nucleic Acids Res. 1977 Nov;4(11):3839-54. doi: 10.1093/nar/4.11.3839.
Structural transition in chromatin was measured as a function of counter ions in solution (NaCl or MgCl(2)) and of histones bound on the DNA. The addition of counter ions to aqueous solutions of chromatin, partially dehistonized chromatin, and DNA caused a drastic reduction in viscosity and a significant increase in sedimentation coefficient. Transitions occurred primarily at about 2 x 10(-3) M NaCl and 1 x 10(-5) M MgCl(2) and are interpreted as a change in structure of chromatin induced by tight binding of cations (Na(+) or Mg(++)) to DNA, either free or bound by histones, and is an intrinsic property of DNA rather than of the type of histone bound. At a given ionic condition, removal of histone H1 from chromatin had only a minor effect on the hydrodynamic properties of chromatin while removal of other histones caused a drastic change in these properties. An increase in the sedimentation coefficient of DNA was observed also for protamine. DNA complexes wherein the bound protein contains only unordered coil rather than the alpha-helices found in histones.
染色质中的结构转变是作为溶液中抗衡离子（氯化钠或氯化镁）以及结合在DNA上的组蛋白的函数来测量的。向染色质、部分脱组蛋白染色质和DNA的水溶液中添加抗衡离子，会导致粘度急剧降低，沉降系数显著增加。转变主要发生在约2×10⁻³M氯化钠和1×10⁻⁵M氯化镁时，这被解释为阳离子（Na⁺或Mg²⁺）与游离或被组蛋白结合的DNA紧密结合所诱导的染色质结构变化，并且是DNA的固有特性而非所结合组蛋白的类型。在给定的离子条件下，从染色质中去除组蛋白H1对染色质的流体动力学性质只有轻微影响，而去除其他组蛋白则会导致这些性质发生剧烈变化。对于鱼精蛋白，也观察到了DNA沉降系数的增加。在DNA复合物中，结合的蛋白质仅包含无规卷曲而非组蛋白中发现的α螺旋。
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