Bechinger B
Max-Planck-Institut für molekulare Physiologie, Dortmund, Germany.
J Mol Biol. 1996 Nov 15;263(5):768-75. doi: 10.1006/jmbi.1996.0614.
Hydrophobic and amphipathic alpha-helices act as independent functional units in immunogenic or fusogenic polypeptides and constitute important structural building blocks in larger membrane proteins. In order to quantitatively assess the interactions that determine the alignment of membrane-associated alpha-helices, hydrophobic model peptides containing histidine residues at selected sites were prepared by solid-phase peptide synthesis. CD and solution NMR spectroscopy show that these peptides assume alpha-helical secondary structures in micellar environments. The chemical shift alterations of the histidine side-chain protons during pH titration experiments indicate that the pK values of the histidine imidazole protons range from 4.9 to 6.6 in the presence of dodecylphosphocholine micelles. 15N solid-state NMR spectroscopy was used to determine the membrane alignment of these peptide alpha-helices in uniaxially oriented phospholipid bilayers. The observed pH-dependent change of orientation of one of these model peptides is quantitatively described by a dynamic equilibrium governed by both electrostatic and hydrophobic protein-lipid interactions. The thermodynamic equations presented provide a means for the prediction of membrane protein structure and topology, as well as the future design of peptide channels and pharmaceuticals.
疏水和亲水两性α螺旋在免疫原性或融合性多肽中作为独立的功能单元起作用，并且是更大膜蛋白中重要的结构构建块。为了定量评估决定膜相关α螺旋排列的相互作用，通过固相肽合成制备了在选定位置含有组氨酸残基的疏水模型肽。圆二色光谱和溶液核磁共振光谱表明，这些肽在胶束环境中呈现α螺旋二级结构。pH滴定实验期间组氨酸侧链质子的化学位移变化表明，在十二烷基磷酰胆碱胶束存在下，组氨酸咪唑质子的pK值范围为4.9至6.6。15N固态核磁共振光谱用于确定这些肽α螺旋在单轴取向磷脂双层中的膜排列。观察到的这些模型肽之一的pH依赖性取向变化由静电和疏水蛋白-脂质相互作用控制的动态平衡定量描述。所提出的热力学方程为预测膜蛋白结构和拓扑以及肽通道和药物的未来设计提供了一种方法。
