XXXX -induced conformational changes of ubiquitin.

@entity10977 @entity4313 @entity167 @entity1853 @entity13756 @entity669 @entity5209
Ubiquitin has been found to be soluble in @entity10977 and @entity4313 as the @entity13756 or @entity5209 salt. When the effect of @entity167 on the structure of ubiquitin is examined, two reversible conformational transitions are observed. Upon lowering the dielectric constant of aqueous @entity167 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 @entity1853 and the single @entity669 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 @entity4313 can be normalized by the use of a dielectric constant scale. This normalization corrects for the different molar volumes of different @entity4313 , allows comparison of results obtained with different @entity4313 , and should be useful in studying this phenomenon with different proteins.
