Protegrin-1 (PG-1), an 18-residue β-hairpin stabilized by two disulfide bonds, is a member of a family of powerful antimicrobial peptides which are believed to act through membrane permeabilization. Here we used a combination of experimental and computational approaches to characterize possible structural arrangements of PG-1 in lipid bilayers mimicking bacterial membranes. We have measured the dose–response function of the PG-1-induced leakage of markers of various sizes from vesicles and found it to be consistent with the formation of pores of two different sizes. The first one allows the release of small dyes and occurs at peptide:lipid ratios < 0.006. Above this ratio, larger pores are observed through which the smallest of dextrans FD4 can be released. In parallel with pore formation, we observe a general large-scale destabilization of vesicles which is probably related to complete rupture of some vesicles. The population of vesicles that are completely ruptured depends linearly on PG-1:lipid ratio. Neither pore size, nor vesicle rupture are influenced by the formation of disulfide bonds. Previous computational work on oxidized protegrin is complemented here by all-atom MD simulations of PG-1 with reduced disulfide bonds both in solution (monomer) and in a bilayer (dimer and octamer). The simulations provide molecular insights into the influence of disulfide bonds on peptide conformation, aggregation, and oligomeric structure.

Protegrin-1 (PG-1) 是一种由两个二硫键稳定的 18 个残基 β-发夹，是强大的抗菌肽家族的成员，据信通过膜透化作用。在这里，我们结合实验和计算方法来表征模拟细菌膜的脂质双层中 PG-1 的可能结构排列。我们测量了 PG-1 诱导的囊泡中各种大小标记物渗漏的剂量反应函数，发现它与两种不同大小的孔的形成一致。第一个允许释放小染料，发生在肽：脂质比率 < 0.006 时。高于该比率，观察到较大的孔，通过这些孔可以释放最小的葡聚糖 FD4。与孔隙形成同时，我们观察到囊泡的普遍大规模不稳定，这可能与某些囊泡的完全破裂有关。完全破裂的囊泡数量与 PG-1: 脂质比率呈线性关系。孔径大小和囊泡破裂均不受二硫键形成的影响。先前关于氧化 protegrin 的计算工作在这里通过 PG-1 的全原子 MD 模拟得到补充，在溶液（单体）和双层（二聚体和八聚体）中具有还原的二硫键。模拟提供了关于二硫键对肽构象、聚集和寡聚结构影响的分子见解。囊泡破裂也不受二硫键形成的影响。先前关于氧化 protegrin 的计算工作在这里通过 PG-1 的全原子 MD 模拟得到补充，在溶液（单体）和双层（二聚体和八聚体）中具有还原的二硫键。模拟提供了关于二硫键对肽构象、聚集和寡聚结构影响的分子见解。囊泡破裂也不受二硫键形成的影响。先前关于氧化 protegrin 的计算工作在这里得到了对 PG-1 的全原子 MD 模拟的补充，该模拟在溶液（单体）和双层（二聚体和八聚体）中都具有还原的二硫键。模拟提供了关于二硫键对肽构象、聚集和寡聚结构影响的分子见解。