Bradbury E M, Cary P D, Crane-Robinson C, Rattle H W, Boublik M, Sautière P
Biochemistry. 1975 May 6;14(9):1876-85. doi: 10.1021/bi00680a012.
Conformational changes in histone H2A (ALK, F2A2, IIbl) as a function of ionic strength and pH have been followed using high resolution nuclear magnetic resonance (NMR), circular dichroism (CD), and infrared (ir). While change in pH from 3 to 7 (no added salt) causes little structural change, added salt induces the formation of both alpha helix (28 percent maximum) and intermolecular associates in the region of the molecule between 25 and 113. No beta structure was observed at high salt. By the use of different salts it was shown that the structural changes were due largely to nonspecific counterion screening by the added anion. Comparison of observed with simulated NMR spectra has led to the proposal that an ionic strength dependent equilibrium exists between largely unstructured coil molecules and fully structured and aggregated molecules. NMR spectra of H2A obtained in the presence of DNA showed that both the N- and C-terminal regions bind to DNA, i.e., not the portion of the chain that is involved in interhistone interactions.
利用高分辨率核磁共振（NMR）、圆二色性（CD）和红外（ir）技术，研究了组蛋白H2A（ALK、F2A2、IIbl）的构象变化与离子强度和pH值的关系。当pH值从3变为7（不添加盐）时，结构变化很小，但添加盐会诱导α螺旋（最大28%）的形成以及分子中25至113区域内分子间缔合体的形成。在高盐条件下未观察到β结构。通过使用不同的盐表明，结构变化主要是由于添加的阴离子进行非特异性抗衡离子屏蔽所致。将观察到的NMR光谱与模拟光谱进行比较后提出，在很大程度上无结构的卷曲分子与完全结构化和聚集的分子之间存在离子强度依赖性平衡。在DNA存在下获得的H2A的NMR光谱表明，N端和C端区域均与DNA结合，即不与参与组蛋白间相互作用的链段结合。
