Wilkinson K D, Mayer A N
Arch Biochem Biophys. 1986 Nov 1;250(2):390-9. doi: 10.1016/0003-9861(86)90741-1.
Ubiquitin has been found to be soluble in ethylene glycol and alcohols as the perchlorate or hydrochloride salt. When the effect of alcohol on the structure of ubiquitin is examined, two reversible conformational transitions are observed. Upon lowering the dielectric constant of aqueous alcohol solutions of ubiquitin from 80 to 45, the native structure of ubiquitin is converted to a form consistent with 50% helical structure. This conformational change results in a change in exposure to solvent of the single methionine and the single tyrosine residues of ubiquitin. In agreement with crystallographic results, these residues are buried in the native conformation but become fully exposed to solvent upon undergoing this transition. Further lowering of the dielectric constant to 20 results in the accumulation of a conformation with almost complete helical structure. Thus, hydrophobic interactions cause facile conformational changes in the ubiquitin structure. These results are discussed in terms of a preferential solvation model. It is shown that the results obtained with different alcohols can be normalized by the use of a dielectric constant scale. This normalization corrects for the different molar volumes of different alcohols, allows comparison of results obtained with different alcohols, and should be useful in studying this phenomenon with different proteins.
已发现泛素以高氯酸盐或盐酸盐的形式可溶于乙二醇和醇类。当研究醇对泛素结构的影响时，观察到两个可逆的构象转变。在将泛素的醇水溶液的介电常数从80降低到45时，泛素的天然结构转变为与50%螺旋结构一致的形式。这种构象变化导致泛素的单个甲硫氨酸和单个酪氨酸残基暴露于溶剂的情况发生变化。与晶体学结果一致，这些残基在天然构象中被掩埋，但在经历这种转变后会完全暴露于溶剂中。进一步将介电常数降低到20会导致几乎完全螺旋结构的构象积累。因此，疏水相互作用导致泛素结构中容易发生构象变化。这些结果根据优先溶剂化模型进行了讨论。结果表明，使用介电常数标度可以对不同醇类获得的结果进行归一化。这种归一化校正了不同醇类的不同摩尔体积，允许比较不同醇类获得的结果，并且在研究不同蛋白质的这种现象时应该是有用的。
