Wieprecht T, Dathe M, Beyermann M, Krause E, Maloy W L, MacDonald D L, Bienert M
Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany.
Biochemistry. 1997 May 20;36(20):6124-32. doi: 10.1021/bi9619987.
The magainins are antibacterial peptides from the skin of Xenopus laevis. They show a broad range of activity against prokaryotic cells but lyse eukaryotic cells poorly. To elucidate the influence of peptide hydrophobicity on membrane activity and selectivity, we designed and synthesized analogs of magainin 2 amide with slightly varying hydrophobicities but retained hydrophobic moment, peptide charge, and angle subtended by the hydrophilic helix region. Circular dichroism investigations of the peptides revealed that all peptides investigated adopt an alpha-helical conformation when bound to phospholipid vesicles. Dye-releasing experiments from vesicles of phosphatidylglycerol (PG) showed that the membrane-permeabilizing activity of the analogs is not influenced by peptide hydrophobicity. In contrast, the permeability-enhancing activity on vesicles bearing high amounts of phosphatidylcholine (PC) increases drastically with enhanced peptide hydrophobicity, resulting in a reduced selectivity of more hydrophobic analogs for negatively charged membranes. Likewise, the peptide affinity to PC-rich membranes increases in the order of hydrophobicity. Correlation of peptide binding and membrane permeabilization of PC/PG (3:1) vesicles revealed that the observed differences in peptide activity on membranes of low negative surface charge are mainly caused by the different binding affinities. The antibacterial and hemolytic activity of the peptides increases with enhanced hydrophobicity. A strong correlation was found between the hemolytic effect and the bilayer-permeabilizing activity against PC-rich vesicles. Whereas the antibacterial specificity of the more hydrophobic analogs is retained for Escherichia coli, the specificity for Pseudomonas aeruginosa decreases with increasing hydrophobicity.
爪蟾抗菌肽是从非洲爪蟾皮肤中提取的抗菌肽。它们对原核细胞具有广泛的活性，但对真核细胞的裂解作用较弱。为了阐明肽疏水性对膜活性和选择性的影响，我们设计并合成了爪蟾抗菌肽2酰胺的类似物，其疏水性略有不同，但保留了疏水矩、肽电荷和亲水螺旋区所对的角度。对这些肽的圆二色性研究表明，所有研究的肽在与磷脂囊泡结合时都采用α-螺旋构象。来自磷脂酰甘油（PG）囊泡的染料释放实验表明，类似物的膜通透活性不受肽疏水性的影响。相反，对含有大量磷脂酰胆碱（PC）的囊泡的通透性增强活性随着肽疏水性的增强而急剧增加，导致疏水性更强的类似物对带负电荷膜的选择性降低。同样，肽对富含PC的膜的亲和力按疏水性顺序增加。PC/PG（3:1）囊泡的肽结合与膜通透相关性表明，观察到的肽在低负表面电荷膜上活性的差异主要是由不同的结合亲和力引起的。肽的抗菌和溶血活性随着疏水性的增强而增加。溶血作用与对富含PC的囊泡的双层通透活性之间存在很强的相关性。虽然疏水性更强的类似物对大肠杆菌仍保留抗菌特异性，但对铜绿假单胞菌的特异性随着疏水性的增加而降低。
