Structural and thermodynamic analyses of the interaction between melittin and lipopolysaccharide
Structural and thermodynamic analyses of the interaction between melittin and lipopolysaccharide
复制标题
DOI：
10.1016/j.bbamem.2007.07.017
复制
发表时间：
2007-12-01
影响因子：
3.4
通讯作者：
Bhattacharjya, Surajit
中科院分区：
文献类型：
--
作者：
Bhunia, Anirban;Domadia, Prema N.;Bhattacharjya, Surajit
脂多糖（LPS）是革兰氏阴性菌外膜的主要成分，是抗菌肽与细菌相互作用的第一个位点。在这项工作中，我们已经确定了蜂毒肽，一个众所周知的膜活性的两亲性肽从蜜蜂毒液，转移核Overhauser效应（Tr-NOE）光谱在其与脂多糖的结合状态下的溶液构象。蜂毒肽的LPS结合构象的特征在于仅限于分子的C-末端区域（残基A15-R24）的螺旋结构。饱和转移差（STD）NMR研究表明，蜂毒肽的几个C-末端残基，包括色氨酸19是在接近LPS。等温滴定量热法（ITC）的数据表明，蜂毒肽结合脂多糖或脂质A是一个吸热过程。蜂毒肽和脂质A之间的相互作用的进一步特征在于2.85 × 10（6）M-1的平衡结合常数（K-a）和蜂毒肽/脂质A的0.80的化学计量。从ITC实验中获得的结合自由能（Δ G（0））估计值为-8.8 kcal mol（-1），与蜂毒肽与LPS复合物的部分螺旋结构密切相关。此外，已发现衍生自蜂毒肽C-末端的合成肽片段，残基L13-Q26或mel-C，含有对大肠杆菌细胞相当的外膜透化活性。蜂毒肽和mel-C的固有色氨酸荧光实验证明在LPS胶束存在下非常相似的发射最大值和淬灭。色氨酸残基的红边激发位移（REES）研究表明，这两种肽在与LPS复合时位于非常相似的环境中。总的来说，这些结果表明，螺旋构象的蜂毒肽，在其C-末端，可能是一个重要的元素，在识别LPS的外膜。(C)2007 Elsevier B.V.保留所有权利。
Lipopolysaccharide (LPS), the major constituent of the outer membrane of Gram-negative bacteria, is the very first site of interactions with the antimicrobial peptides. In this work, we have determined a solution conformation of melittin, a well-known membrane active amphiphilic peptide from honey bee venom, by transferred nuclear Overhauser effect (Tr-NOE) spectroscopy in its bound state with lipopolysaccharide. The LPS bound conformation of melittin is characterized by a helical structure restricted only to the C-terminus region (residues A15-R24) of the molecule. Saturation transfer difference (STD) NMR studies reveal that several C-terminal residues of melittin including Trp 19 are in close proximity with LPS. Isothermal titration calorimetry (ITC) data demonstrates that melittin binding to LPS or lipid A is an endothermic process. The interaction between melittin and lipid A is further characterized by an equilibrium association constant (K-a) of 2.85 x 10(6) M-1 and a stoichiometry of 0.80, melittin/lipid A. The estimated free energy of binding (Delta G(0)), - 8.8 kcal mol(-1), obtained from ITC experiments correlates well with a partial helical structure of melittin in complex with LPS. Moreover, a synthetic peptide fragment, residues L13-Q26 or mel-C, derived from the C-terminus of melittin has been found to contain comparable outer membrane permeabilizing activity against Escherichia coli cells. Intrinsic tryptophan fluorescence experiments of melittin and mel-C demonstrate very similar emission maxima and quenching in presence of LPS micelles. The Red Edge Excitation Shift (REES) studies of tryptophan residue indicate that both peptides are located in very similar environment in complex with LPS. Collectively, these results suggest that a helical conformation of melittin, at its C-terminus, could be an important element in recognition of LPS in the outer membrane. (C) 2007 Elsevier B.V. All rights reserved.