Effect of guanidine hydrochloride on the hydrodynamic and thermodynamic properties of human apolipoprotein A-I in solution.

作者：Celina Edelstein, Antonio Mario Scanu · 发表于：Journal of Biological Chemistry · 年份：1980 · DOI：10.1016/s0021-9258(19)70693-0 · 被引用次数：58 · 研究领域：Protein Structure and Dynamics、Protein Interaction Studies and Fluorescence Analysis、Molecular spectroscopy and chirality

To further define its properties in solution, the course of denaturation of apolipoprotein A-I (apo-A-I) was studied as a function of various concentrations of guanidine hydrochloride (GdmCl) using the techniques of circular dichroism, ultraviolet difference spectroscopy, analytical ultracentrifugation, viscometry, and densitometry. At low molarities of GdmCl (0 to 0.4 M), apoA-I exhibited anomalous ellipticity changes which were dependent upon apo-A-I concentration; from ultracentrifugal studies, these changes were interpreted as related to the dissociation of protein oligomers into a new equilibrium attended by a preferential interaction with GdmCl (0.07 g/g of apo-A-I and an increase in molar volume, 197 ml). On the other hand, the frictional (1.68) and axial (5.7) ratios were similar to those in the native state. At molarities of GdmCl between 0.4 M and 6 M, apo-A-I dissociated into monomers by a cooperative denaturation process which was independent of protein concentration: both dissociation and denaturation were thermodynamically reversible with an apparent free energy of stabilization, = 3.70 kcal/mol. Between 2 and 6 M GdmC1, changes in the conformation, intrinsic viscosity, and volume of apo-A-I were noted as assessed by spectroscopic, viscometric, and partial specific volume measurements. These changes appeared related to the number of moles of GdmCl bound to apo-A-I (at 2 M GdmC1, 63 mol; at 6 M, 181 mol).