Matsuzaki K, Nakamura A, Murase O, Sugishita K, Fujii N, Miyajima K
Faculty of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Japan.
Biochemistry. 1997 Feb 25;36(8):2104-11. doi: 10.1021/bi961870p.
Magainin 2, an antimicrobial peptide from Xenopus skin, assumes an amphiphilic helix when bound to acidic phospholipids, forming a pore composed of a dynamic, peptide-lipid supramolecular complex [Matsuzaki et al. (1996) Biochemistry 35, 11361-11368]. Upon the disintegration of the pore, a fraction of the peptide molecules stochastically translocates across the bilayer (Matsuzaki, et al., 1995). In order to investigate the effects of peptide charge on the magainin 2-lipid bilayer interactions, we synthesized four magainin 2 analogs with different charges (0-6+). MG0: K10E, K11E, F12W-magainin 2. MG2+: K10E, F12W-magainin 2. MG4+: F12W-magainin 2. MG6+: F12W, E19Q-magainin 2 amide. An increase in charge resulted in a stronger binding of the peptide to the negatively charged membranes, suggesting that electrostatic attractions play a crucial role in the binding process. The helical stability in a trifluoroethanol/buffer mixture was decreased with increasing positive charge because of electrostatic repulsions between the closely spaced positive side chains, whereas the helicity in the lipid bilayer was much higher and appeared to be independent of the peptide charge. However, enhanced repulsions between the highly positively charged helices destabilized the pore. Therefore, the efficiency of the most basic peptide (MG6+) to translocate across the bilayer was the greatest by virtue of the short life span of its pore and the very tight membrane binding. The charge distribution of wild-type magainin 2 was found to be so designed as to exhibit the maximal lytic activity by simultaneously achieving a strong binding and a moderate pore stability.
爪蟾抗菌肽2（Magainin 2）是一种来自非洲爪蟾皮肤的抗菌肽，当与酸性磷脂结合时会形成两亲性螺旋结构，进而形成由动态的肽 - 脂质超分子复合物组成的孔道[松崎等人（1996年），《生物化学》第35卷，11361 - 11368页]。孔道解体后，一部分肽分子会随机穿过双层膜（松崎等人，1995年）。为了研究肽电荷对爪蟾抗菌肽2与脂质双层相互作用的影响，我们合成了四种带有不同电荷（0 - 6 +）的爪蟾抗菌肽2类似物。MG0：K10E、K11E、F12W - 爪蟾抗菌肽2。MG2 +：K10E、F12W - 爪蟾抗菌肽2。MG4 +：F12W - 爪蟾抗菌肽2。MG6 +：F12W、E19Q - 爪蟾抗菌肽2酰胺。电荷增加导致肽与带负电荷的膜结合更强，这表明静电引力在结合过程中起关键作用。在三氟乙醇/缓冲液混合物中，由于紧密排列的正侧链之间的静电排斥，随着正电荷增加，螺旋稳定性降低，而在脂质双层中的螺旋度更高，且似乎与肽电荷无关。然而，高度带正电荷的螺旋之间增强的排斥作用使孔道不稳定。因此，由于其孔道寿命短且与膜结合非常紧密，最碱性的肽（MG6 +）穿过双层膜的效率最高。研究发现，野生型爪蟾抗菌肽2的电荷分布经过精心设计，通过同时实现强结合和适度的孔道稳定性来展现最大的裂解活性。
