Colles S M, Woodford J K, Moncecchi D, Myers-Payne S C, McLean L R, Billheimer J T, Schroeder F
Department of Pharmacology and Cell Biophysics, University of Cincinnati Medical Center, Ohio 45267-0004, USA.
Lipids. 1995 Sep;30(9):795-803. doi: 10.1007/BF02533954.
The interaction of human recombinant sterol carrier protein-2 (SCP-2) with sterols was examined. Two independent ligand binding methods, Lipidex 1000 binding of [3H]cholesterol and a fluorescent dehydroergosterol binding assay, were used to determine the affinity of SCP-2 for sterols. Binding analysis indicated SCP-2 bound [3H]cholesterol and dehydroergosterol with a Kd of 0.3 and 1.7 microM, respectively, and suggested the presence of a single binding site. Phase fluorometry and circular dichroism were used to characterize the SCP-2 sterol binding site. Alterations in dehydroergosterol lifetime, SCP-2 tryptophan lifetime, and SCP-2 tryptophan quenching by acrylamide upon cholesterol binding demonstrated a shielding of the SCP-2 tryptophan from the aqueous solvent by bound sterol. Differential polarized phase fluorometry revealed decreased SCP-2 tryptophan rotational correlation time upon cholesterol binding. Circular dichroism of SCP-2 indicated that cholesterol elicited a small decrease in SCP-2 alpha helical content. The data suggest that SCP-2 binds sterols with affinity consistent with a lipid transfer protein that may act either as an aqueous carrier or at a membrane surface to enhance sterol desorption.
对人重组固醇载体蛋白-2（SCP-2）与固醇的相互作用进行了研究。采用两种独立的配体结合方法，即[3H]胆固醇的Lipidex 1000结合法和荧光脱氢麦角固醇结合测定法，来确定SCP-2对固醇的亲和力。结合分析表明，SCP-2与[3H]胆固醇和脱氢麦角固醇结合的解离常数（Kd）分别为0.3和1.7微摩尔，并提示存在单一结合位点。利用相荧光测定法和圆二色性来表征SCP-2的固醇结合位点。胆固醇结合后，脱氢麦角固醇寿命、SCP-2色氨酸寿命以及丙烯酰胺对SCP-2色氨酸的淬灭作用发生改变，表明结合的固醇将SCP-2色氨酸与水相溶剂隔离开来。差分偏振相荧光测定法显示，胆固醇结合后SCP-2色氨酸的旋转相关时间缩短。SCP-2的圆二色性表明，胆固醇使SCP-2的α螺旋含量略有降低。数据表明，SCP-2以与脂质转运蛋白相符的亲和力结合固醇，该脂质转运蛋白既可以作为水相载体发挥作用，也可以在膜表面发挥作用以增强固醇解吸。
