Lequin Olivier, Bruston Francine, Convert Odile, Chassaing Gérard, Nicolas Pierre
UMR 7613 CNRS, Université Paris 6, Structure et fonction de molécules bioactives, Université Pierre et Marie Curie, Case Courrier 45, 4 Place Jussieu, 75252 Paris Cedex 05, France.
Biochemistry. 2003 Sep 2;42(34):10311-23. doi: 10.1021/bi034401d.
Dermaseptins are antimicrobial peptides from frog skin that have high membrane-lytic activity against a broad spectrum of microorganisms. The structure of dermaseptin B2 in aqueous solution, in TFE/water mixtures, and in micellar and nonmicellar SDS was analyzed by CD, FTIR, fluorescence, and NMR spectroscopy combined with molecular dynamics calculations. Dermaseptin B2 is unstructured in water, but helical conformations, mostly in segment 3-18, are stabilized by addition of TFE. SDS titration showed that dermaseptin B2 assumes nonhelical structures at SDS concentrations far below the critical micellar concentration and helical structures at micellar concentrations. Dermaseptin B2 bound to SDS micelles (0.4 mM peptide, 80 mM SDS) adopts a well-defined amphipathic helix between residues 11-31 connected to a more flexible helical segment spanning residues 1-8 by a flexible hinge region around Val9 and Gly10. Experiments using paramagnetic probes showed that dermaseptin B2 lies near the surface of SDS micelles and that residue Trp3 is buried in the SDS micelle, but close to the surface. A slow exchange equilibrium occurs at higher peptide/SDS ratios (2 mM peptide, 80 mM SDS) between forms having distinct sets of resonances in the N-terminal 1-11 segment. This equilibrium could reflect different oligomeric states of dermaseptin B2 interacting with SDS micelles. Structure-activity studies on dermaseptin B2 analogues showed that the N-terminal 1-11 segment is an absolute requirement for antibacterial activity, while the C-terminal 10-33 region is also important for full antibiotic activity.
皮肤防御素是从蛙皮中提取的抗菌肽，对多种微生物具有高膜裂解活性。通过圆二色光谱（CD）、傅里叶变换红外光谱（FTIR）、荧光光谱和核磁共振光谱（NMR）结合分子动力学计算，分析了皮肤防御素B2在水溶液、TFE/水混合物、胶束和非胶束SDS中的结构。皮肤防御素B2在水中无结构，但添加TFE可稳定其螺旋构象，主要在3 - 18片段。SDS滴定表明，在远低于临界胶束浓度的SDS浓度下，皮肤防御素B2呈现非螺旋结构，而在胶束浓度下呈现螺旋结构。与SDS胶束结合的皮肤防御素B2（0.4 mM肽，80 mM SDS）在11 - 31位残基之间形成明确的两亲性螺旋，通过围绕Val9和Gly10的柔性铰链区与跨越1 - 8位残基的更灵活的螺旋片段相连。使用顺磁探针进行的实验表明，皮肤防御素B2位于SDS胶束表面附近，Trp3残基埋在SDS胶束中，但靠近表面。在较高的肽/SDS比例（2 mM肽，80 mM SDS）下，N端1 - 11片段中具有不同共振组的形式之间会发生缓慢的交换平衡。这种平衡可能反映了与SDS胶束相互作用的皮肤防御素B2的不同寡聚状态。对皮肤防御素B2类似物的构效关系研究表明，N端1 - 11片段是抗菌活性的绝对必要条件，而C端10 - 33区域对充分的抗菌活性也很重要。
