Liu Z P, Rizo J, Gierasch L M
Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas 75235-9041.
Biochemistry. 1994 Jan 11;33(1):134-42. doi: 10.1021/bi00167a017.
We have examined the conformational behavior under various unfolding conditions of a predominantly beta-sheet protein, cellular retinoic acid binding protein (CRABP). Urea unfolding-refolding of CRABP is a highly cooperative process that can be approximated by a two-state model. Acid denaturation is also cooperative and reversible and leads to a state containing nonnative residual structure: Below pH 2.6, CRABP contains a substantially larger amount of alpha-helix than under native conditions. CRABP adopts up to 75% alpha-helix in solutions containing a high percentage of 2,2,2-trifluoroethanol. The acid-denatured state of CRABP undergoes a conformational change to a state containing predominantly beta-sheet structure upon the addition of small amounts of Na2SO4. This conformational malleability may be important for the folding mechanism of CRABP. The possible implication of nonnative alpha-helical structure in the folding of CRABP is discussed.
我们研究了一种主要为β-折叠结构的蛋白质——细胞视黄酸结合蛋白（CRABP）在各种去折叠条件下的构象行为。CRABP的尿素去折叠-复性过程是一个高度协同的过程，可用两态模型近似描述。酸变性也是协同且可逆的，并导致一种含有非天然残余结构的状态：在pH 2.6以下，CRABP含有的α-螺旋量比天然条件下显著更多。在含有高比例2,2,2-三氟乙醇的溶液中，CRABP可形成高达75%的α-螺旋。加入少量Na2SO4后，CRABP的酸变性状态会发生构象变化，转变为一种主要为β-折叠结构的状态。这种构象可塑性可能对CRABP的折叠机制很重要。文中还讨论了非天然α-螺旋结构在CRABP折叠过程中的可能影响。
