Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697, USA.
Department of Chemistry, University of California, Irvine, CA 92697, USA.
Biomolecules. 2020 Jul 17;10(7):1069. doi: 10.3390/biom10071069.
The Droserasins, aspartic proteases from the carnivorous plant , contain a 100-residue plant-specific insert (PSI) that is post-translationally cleaved and independently acts as an antimicrobial peptide. PSIs are of interest not only for their inhibition of microbial growth, but also because they modify the size of lipid vesicles and strongly interact with biological membranes. PSIs may therefore be useful for modulating lipid systems in NMR studies of membrane proteins. Here we present the expression and biophysical characterization of the Droserasin 1 PSI (D1 PSI.) This peptide is monomeric in solution and maintains its primarily α -helical secondary structure over a wide range of temperatures and pH values, even under conditions where its three disulfide bonds are reduced. Vesicle fusion assays indicate that the D1 PSI strongly interacts with bacterial and fungal lipids at pH 5 and lower, consistent with the physiological pH of mucilage. It binds lipids with a variety of head groups, highlighting its versatility as a potential stabilizer for lipid nanodiscs. Solid-state NMR spectra collected at a field strength of 36 T, using a unique series-connected hybrid magnet, indicate that the peptide is folded and strongly bound to the membrane. Molecular dynamics simulations indicate that the peptide is stable as either a monomer or a dimer in a lipid bilayer. Both the monomer and the dimer allow the passage of water through the membrane, albeit at different rates.
食虫植物捕蝇草中的 Droserasins 是一种天冬氨酸蛋白酶，包含一个 100 个残基的植物特异性插入序列（PSI），该序列在翻译后被切割并独立作为一种抗菌肽发挥作用。PSI 不仅因其抑制微生物生长而受到关注，还因为它们可以改变脂质体的大小，并与生物膜强烈相互作用。因此，PSI 可能有助于调节脂质系统，用于膜蛋白的 NMR 研究。在这里，我们展示了 Droserasin 1 PSI（D1 PSI）的表达和生物物理特性。该肽在溶液中呈单体形式，在很宽的温度和 pH 值范围内保持其主要的α-螺旋二级结构，即使在其三个二硫键被还原的情况下也是如此。囊泡融合实验表明，D1 PSI 在 pH5 及更低时与细菌和真菌脂质强烈相互作用，与粘液的生理 pH 值一致。它与具有各种头基的脂质结合，突出了其作为潜在脂质纳米盘稳定剂的多功能性。使用独特的串联混合磁体在 36T 的场强下收集的固态 NMR 谱表明，该肽在膜上折叠并与膜强烈结合。分子动力学模拟表明，该肽在脂质双层中无论是单体还是二聚体都是稳定的。单体和二聚体都允许水通过膜，但速率不同。
