Garel A, Kovacs A M, Champagne M, Daune M
Biochim Biophys Acta. 1975 Jun 2;395(1):5-15. doi: 10.1016/0005-2787(75)90228-2.
Purified chicken erythrocyte histones FV and F2a2 were studied by means of circular dichroism as a function of ionic strength and temperature. The percentage of alpha-helical regions was calculated by comparison with reference spectra obtained with four standard proteins of known tertiary structure. Maximal alpha-helical organization, reached in high ionic strength, was estimated to 14% and 23% for FV and F2a2 respectively. We have compared our experimental determinations of the secondary structure of F2a2 with predictions made from amino-acid sequence according to Fasman's rules. When instability induced by the presence of charged residues close together is taken into account, a good agreement is found between predicted and observed values. The thermal denaturation of FV is cooperative and, unlike F2a2, seems to obey a two-state transition. The classical Arrhenius plot is linear, which indicates that the heat capacity is the same in both the native and the denatured state. Such a behaviour is typical of an expanded configuration of FV even in the "native" state.
利用圆二色性研究了纯化的鸡红细胞组蛋白FV和F2a2，其作为离子强度和温度的函数。通过与四种已知三级结构的标准蛋白质获得的参考光谱进行比较，计算出α-螺旋区域的百分比。在高离子强度下达到的最大α-螺旋结构，FV和F2a2分别估计为14%和23%。我们将F2a2二级结构的实验测定结果与根据法斯曼规则从氨基酸序列做出的预测进行了比较。当考虑到相邻带电残基的存在所引起的不稳定性时，预测值与观测值之间发现了良好的一致性。FV的热变性是协同的，与F2a2不同，它似乎遵循两态转变。经典的阿累尼乌斯图是线性的，这表明在天然状态和变性状态下的热容是相同的。即使在“天然”状态下，这种行为也是FV扩展构型的典型特征。
