Bourassa P, Bekale L, Tajmir-Riahi H A
Département de Chimie-Biologie, Université du Québec à Trois-Rivières, C.P. 500, Trois-Rivières, QC, Canada G9A 5H7.
Département de Chimie-Biologie, Université du Québec à Trois-Rivières, C.P. 500, Trois-Rivières, QC, Canada G9A 5H7.
Int J Biol Macromol. 2014 Sep;70:156-66. doi: 10.1016/j.ijbiomac.2014.06.038. Epub 2014 Jun 28.
We report the molecular interaction and the binding sites of cholesterol (CHOL), 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), dioctadecyldimethyl-ammoniumbromide (DDAB), and dioleoylphosphatidylethanolamine (DOPE) with milk α- and β-caseins in aquous solution at physiological conditions. Fourier transform infrared (FTIR), fluorescence spectroscopic methods and molecular modeling were used to determine the binding sites of lipid-protein complexes and the effect of lipid interaction on the stability and conformation of α- and β-caseins. Structural analysis showed that lipids bind casein via mainly hydrophobic contact with association constants of KCHOL-α-casein=1.0 (±0.1)×10(4) M(-1), KDOPE-α-casein=5.0 (±0.07)×10(3) M(-1), KDDAB-α-casein=2.0 (±0.06)×10(4) M(-1), KDOTAP-α-casein=1.5 (±0.6)×10(4) M(-1), KCHOL-β-casein=1.0 (±0.3)×10(4) M(-1), KDOPE-β-casein=1.5 (±0.06)×10(3) M(-1), KDDAB-β-casein=1.7 (±0.3)×10(4) M(-1) and KDOTAP-β-casein=2.1 (±0.5)×10(4) M(-1). The average number of binding sites occupied by lipid molecules on protein (n) were from 0.7 to 1.1. Docking showed different binding sites for α- and β-caseins toward lipid complexation with the free binding energies from -10 to -13 kcal/mol. Casein conformation was altered by lipid interaction with a reduction of α-helix and β-sheet and an increase of random coil and turn structure suggesting a partial protein unfolding.
Cascasein; CHOLcholesterol; DOTAP1,2-dioleoyl-3-trimethylammonium-propane; DDABdioctadecyldimethylammonium bromide; DOPEdioleoylphosphatidylethanolamine; FTIRFourier transform infrared spectroscopy; CDcircular dichroism.
我们报道了在生理条件下，胆固醇（CHOL）、1,2 - 二油酰基 - 3 - 三甲基铵丙烷（DOTAP）、二辛基二甲基溴化铵（DDAB）和二油酰磷脂酰乙醇胺（DOPE）与牛奶α - 和β - 酪蛋白在水溶液中的分子相互作用及结合位点。采用傅里叶变换红外光谱（FTIR）、荧光光谱法和分子模拟来确定脂质 - 蛋白质复合物的结合位点以及脂质相互作用对α - 和β - 酪蛋白稳定性和构象的影响。结构分析表明，脂质主要通过疏水接触与酪蛋白结合，其缔合常数分别为：KCHOL - α - 酪蛋白 = 1.0（±0.1）×10⁴ M⁻¹，KDOPE - α - 酪蛋白 = 5.0（±0.07）×10³ M⁻¹，KDDAB - α - 酪蛋白 = 2.0（±0.06）×10⁴ M⁻¹，KDOTAP - α - 酪蛋白 = 1.5（±0.6）×10⁴ M⁻¹，KCHOL - β - 酪蛋白 = 1.0（±0.3）×10⁴ M⁻¹，KDOPE - β - 酪蛋白 = 1.5（±0.06）×10³ M⁻¹，KDDAB - β - 酪蛋白 = 1.7（±0.3）×10⁴ M⁻¹，KDOTAP - β - 酪蛋白 = 2.1（±0.5）×10⁴ M⁻¹。脂质分子在蛋白质上占据的结合位点平均数量（n）为0.7至1.1。对接显示α - 和β - 酪蛋白与脂质复合的结合位点不同，自由结合能为 - 10至 - 13千卡/摩尔。脂质相互作用改变了酪蛋白的构象，α - 螺旋和β - 折叠减少，无规卷曲和转角结构增加，表明蛋白质部分展开。
Cascasein；CHOLcholesterol；DOTAP1,2 - 二油酰基 - 3 - 三甲基铵丙烷；DDAB二辛基二甲基溴化铵；DOPE二油酰磷脂酰乙醇胺；FTIR傅里叶变换红外光谱；CD圆二色性
