Dings Ruud P M, Haseman Judith R, Mayo Kevin H
Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota Health Sciences Center, 6-155 Jackson Hall, 321 Church Street, Minneapolis, MN 55455, USA.
Biochem J. 2008 Aug 15;414(1):143-50. doi: 10.1042/BJ20080506.
Cationic peptides, known to disrupt bacterial membranes, are being developed as promising agents for therapeutic intervention against infectious disease. In the present study, we investigate structure-activity relationships in the bacterial membrane disruptor betapep-25, a peptide 33-mer. For insight into which amino acid residues are functionally important, we synthesized alanine-scanning variants of betapep-25 and assessed their ability to kill bacteria (Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus) and to neutralize LPS (lipopolysaccharide). Activity profiles were found to vary with the bacterial strain examined. Specific cationic and smaller hydrophobic alkyl residues were crucial to optimal bactericidal activity against the Gram-negative bacteria, whereas larger hydrophobic and cationic residues mediated optimal activity against Gram-positive Staph. aureus. Lysine-substituted norleucine (n-butyl group) variants demonstrated that both charge and alkyl chain length mediate optimal activity. In terms of LPS neutralization, activity profiles were essentially the same against four species of LPS (E. coli 055 and 0111, Salmonella enterica serotype Typhimurium and Klebsiella pneumoniae), and different for two others (Ps. aeruginosa and Serratia marcescens), with specific hydrophobic, cationic and, surprisingly, anionic residues being functionally important. Furthermore, disulfide-bridged analogues demonstrated that an anti parallel beta-sheet structure is the bioactive conformation of betapep-25 in terms of its bactericidal, but not LPS endotoxin neutralizing, activity. Moreover, betapep-25 variants, like the parent peptide, do not lyse eukaryotic cells. This research contributes to the development and design of novel antibiotics.
已知能破坏细菌膜的阳离子肽正被开发为治疗传染病的有前景的药物。在本研究中，我们研究了细菌膜破坏剂betapep-25（一种33肽）的构效关系。为了深入了解哪些氨基酸残基具有重要功能，我们合成了betapep-25的丙氨酸扫描变体，并评估了它们杀死细菌（大肠杆菌、铜绿假单胞菌和金黄色葡萄球菌）以及中和脂多糖（LPS）的能力。发现活性谱因所检测的细菌菌株而异。特定的阳离子和较小的疏水烷基残基对于对革兰氏阴性菌的最佳杀菌活性至关重要，而较大的疏水和阳离子残基介导了对革兰氏阳性金黄色葡萄球菌的最佳活性。赖氨酸取代的正亮氨酸（正丁基）变体表明电荷和烷基链长度都介导了最佳活性。就LPS中和而言，对四种LPS（大肠杆菌055和0111、鼠伤寒沙门氏菌和肺炎克雷伯菌）的活性谱基本相同，而对另外两种（铜绿假单胞菌和粘质沙雷氏菌）则不同，特定的疏水、阳离子以及令人惊讶的阴离子残基具有重要功能。此外，二硫键桥连类似物表明，就其杀菌活性而非LPS内毒素中和活性而言，反平行β-折叠结构是betapep-25的生物活性构象。此外，betapep-25变体与亲本肽一样，不会裂解真核细胞。这项研究有助于新型抗生素的开发和设计。
