Beaudette N V, Okabayashi H, Fasman G D
Biochemistry. 1982 Apr 13;21(8):1765-72. doi: 10.1021/bi00537a011.
Changes in the conformations of H3-H4, H2A-H2B, and the core histone complex brought about by the addition of organic solvents have been examined by circular dichroism spectroscopy. All three complexes assume increased alpha helicity with increasing amounts of the organic solvent. An amount of secondary structure equal to that obtained in phosphate-buffered 2 M NaCl solution can be induced in low-salt solutions of the complexes by the addition of 40-50% ethylene glycol, 50% glycerol, or approximately 2% hexafluoro-2-propanol. H3-H4 was found to be somewhat more flexible than H2A-H2B in its response to changes in solvent polarity. Upon being heated, H3-H4 and the core histone complex both undergo irreversible alpha leads to beta transitions in 50% ethylene glycol under low-salt conditions, while H2A-H2B undergoes an essentially reversible alpha leads to beta random-coil transition under the same conditions. These results are discussed in terms of the dynamics of the nucleosome particle.
通过圆二色光谱法研究了添加有机溶剂后H3-H4、H2A-H2B和核心组蛋白复合物构象的变化。随着有机溶剂用量的增加，这三种复合物的α螺旋度均增加。通过添加40-50%的乙二醇、50%的甘油或约2%的六氟-2-丙醇，可在复合物的低盐溶液中诱导出与在磷酸盐缓冲的2M NaCl溶液中获得的二级结构量相等的二级结构。发现H3-H4在对溶剂极性变化的响应中比H2A-H2B更具柔韧性。在低盐条件下加热时，H3-H4和核心组蛋白复合物在50%乙二醇中均会发生不可逆的α向β转变，而H2A-H2B在相同条件下会发生基本可逆的α向β无规卷曲转变。根据核小体颗粒的动力学对这些结果进行了讨论。
