Department of Physics, University of South Florida, Tampa, FL 33620, United States of America; MED-Cancer & Cell Biology, University of Cincinnati, Cincinnati, OH 45267.
National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, United States of America.
Biochim Biophys Acta Biomembr. 2022 Jul 1;1864(7):183907. doi: 10.1016/j.bbamem.2022.183907. Epub 2022 Mar 2.
Amphiphysin and endophilin are two members of the N-BAR protein family. We have reported membrane interactions of the helix 0 of endophilin (H0-Endo). Here we investigate membrane modulations caused by the helix 0 of amphiphysin (H0-Amph). Electron paramagnetic resonance (EPR) spectroscopy was used to explore membrane properties. H0-Amph was found to reduce lipid mobility, make the membrane interior more polar, and decrease lipid chain orientational order. The EPR data also showed that for anionic membranes, H0-Endo acted as a more potent modulator. For instance, at peptide-to-lipid (P/L) ratio of 1/20, the peak-to-peak splitting was increased by 0.27 G and 1.89 G by H0-Amph and H0-Endo, respectively. Similarly, H0-Endo caused a larger change in the bilayer polarity than H0-Amph (30% versus 12% at P/L = 1/20). At P/L = 1/50, the chain orientational order was decreased by 26% and 66% by H0-Amph and H0-Endo, respectively. The different capabilities were explained by considering hydrophobicity score distributions. We employed atomic force microscopy to investigate membrane structural changes. Both peptides caused the formation of micron-sized holes. Interestingly, only H0-Amph induced membrane fusion as evidenced by the formation of high-rise regions. Lastly, experiments of giant unilamellar vesicles showed that H0-Amph and H0-Endo generated thin tubules and miniscule vesicles, respectively. Together, our studies showed that both helices are effective in altering membrane properties; the observed changes might be important for membrane curvature induction. Importantly, comparisons between the two peptides revealed that the degree of membrane remodeling is dependent on the sequence of the N-terminal helix of the N-BAR protein family.
amphiphysin 和 endophilin 是 N-BAR 蛋白家族的两个成员。我们已经报道了 endophilin 的螺旋 0（H0-Endo）与膜的相互作用。在这里，我们研究了 amphiphysin 的螺旋 0（H0-Amph）引起的膜调制。电子顺磁共振（EPR）光谱被用于研究膜性质。发现 H0-Amph 降低了脂类的流动性，使膜内部更具极性，并降低了脂类链的取向有序性。EPR 数据还表明，对于阴离子膜，H0-Endo 是一种更有效的调节剂。例如，在肽-脂（P/L）比为 1/20 时，H0-Amph 和 H0-Endo 分别使峰-峰分裂增加了 0.27 G 和 1.89 G。同样，H0-Endo 引起的双层极性变化大于 H0-Amph（在 P/L 为 1/20 时分别为 30%和 12%）。在 P/L 为 1/50 时，H0-Amph 和 H0-Endo 分别使链取向有序性降低了 26%和 66%。通过考虑疏水性评分分布，解释了这种不同的能力。我们采用原子力显微镜研究了膜结构的变化。两种肽都导致了微米大小的孔的形成。有趣的是，只有 H0-Amph 诱导了膜融合，这可以从高隆起区域的形成中得到证明。最后，巨大的单层囊泡实验表明，H0-Amph 和 H0-Endo 分别产生了薄管和微小囊泡。总之，我们的研究表明，这两个螺旋都能有效地改变膜性质；观察到的变化可能对膜曲率诱导很重要。重要的是，对这两种肽的比较表明，膜重塑的程度取决于 N-BAR 蛋白家族 N 端螺旋的序列。
