Yau W M, Wimley W C, Gawrisch K, White S H
National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland 20852, USA.
Biochemistry. 1998 Oct 20;37(42):14713-8. doi: 10.1021/bi980809c.
One of the ubiquitous features of membrane proteins is the preference of tryptophan and tyrosine residues for membrane surfaces that presumably arises from enhanced stability due to distinct interfacial interactions. The physical basis for this preference is widely believed to arise from amphipathic interactions related to imino group hydrogen bonding and/or dipole interactions. We have examined these and other possibilities for tryptophan's interfacial preference by using 1H magic angle spinning (MAS) chemical shift measurements, two-dimensional (2D) nuclear Overhauser effect spectroscopy (2D-NOESY) 1H MAS NMR, and solid state 2H NMR to study the interactions of four tryptophan analogues with phosphatidylcholine membranes. We find that the analogues reside in the vicinity of the glycerol group where they all cause similar modest changes in acyl chain organization and that hydrocarbon penetration was not increased by reduction of hydrogen bonding or electric dipole interaction ability. These observations rule out simple amphipathic or dipolar interactions as the physical basis for the interfacial preference. More likely, the preference is dominated by tryptophan's flat rigid shape that limits access to the hydrocarbon core and its pi electronic structure and associated quadrupolar moment (aromaticity) that favor residing in the electrostatically complex interface environment.
膜蛋白普遍存在的一个特征是色氨酸和酪氨酸残基倾向于膜表面，这可能是由于独特的界面相互作用增强了稳定性所致。人们普遍认为这种偏好的物理基础源于与亚氨基氢键和/或偶极相互作用相关的两亲性相互作用。我们通过使用1H魔角旋转（MAS）化学位移测量、二维（2D）核Overhauser效应光谱（2D-NOESY）1H MAS NMR以及固态2H NMR来研究四种色氨酸类似物与磷脂酰胆碱膜的相互作用，从而检验了色氨酸界面偏好的这些及其他可能性。我们发现这些类似物位于甘油基团附近，它们在那里都会使酰基链组织发生类似的适度变化，并且氢键或电偶极相互作用能力的降低并不会增加碳氢化合物的渗透。这些观察结果排除了简单的两亲性或偶极相互作用作为界面偏好的物理基础。更有可能的是，这种偏好主要由色氨酸扁平的刚性形状决定，该形状限制了其进入碳氢化合物核心，以及其π电子结构和相关的四极矩（芳香性），这些因素使得色氨酸倾向于存在于静电复杂的界面环境中。
