Ghosh Suvankar, Pandit Gopal, Debnath Swapna, Chatterjee Sunanda, Satpati Priyadarshi
Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati Guwahati 781039 Assam India
Department of Chemistry, Indian Institute of Technology Guwahati Guwahati 781039 Assam India
RSC Adv. 2021 Nov 17;11(58):36836-36849. doi: 10.1039/d1ra06772a. eCollection 2021 Nov 10.
Recently, we reported a cationic 14 residue peptide LL-14 (LKWLKKLLKWLKKL) with salt-sensitive broad-spectrum antimicrobial potency. However, the mechanism of its salt (NaCl) sensitivity remained unclear. In this study, we have reported computational (∼14.2 μs of MD) and experimental (CD, fluorescence) investigations to examine the salt-sensitivity and the role of peptide secondary structure on LL-14 binding to simple membrane mimetic (SDS, DPC) systems. LL-14 was shown to adopt a random coil (P) conformation in water and α-helical conformation (P) in the peptide:SDS micelle complex, accompanied by tryptophan burial, using both simulations and experiments. Simulations successfully deconvoluted the LL-14:micelle binding event in terms of secondary structure (random coil P helix P) and gave atomic insight into the initial and final LL-14:SDS complexes. Electrostatics drove the N-terminus (L1 and K2) of LL-14 (P or P) to bind the SDS micellar surface, initiating complex formation. LL-14 in amphipathic P conformation bound faster and buried deeper into the SDS micelle relative to P. Increasing NaCl concentration incrementally delayed LL-14:micelle binding by shielding the overall charges of the interacting partners. LL-14 binding to the SDS micelle was significantly faster relative to that of the zwitterionic DPC micelle due to electrostatic reasons. Cationic α-helical amphipathic peptides (with positively charged N-terminus) with low salt-ion concentration seemed to be ideal for faster SDS binding.
最近，我们报道了一种具有盐敏性广谱抗菌活性的阳离子14残基肽LL-14（LKWLKKLLKWLKKL）。然而，其盐（NaCl）敏感性的机制仍不清楚。在本研究中，我们报告了计算（约14.2微秒的分子动力学模拟）和实验（圆二色光谱、荧光）研究，以考察LL-14与简单膜模拟物（十二烷基硫酸钠、二甲基辛酰基磷脂酰胆碱）系统结合时的盐敏感性及肽二级结构的作用。通过模拟和实验均表明，LL-14在水中呈无规卷曲（P）构象，在肽：十二烷基硫酸钠胶束复合物中呈α-螺旋构象（P），同时色氨酸被掩埋。模拟成功地从二级结构（无规卷曲P→螺旋P）方面解析了LL-14：胶束结合事件，并对初始和最终的LL-14：十二烷基硫酸钠复合物进行了原子水平的洞察。静电作用促使LL-14（P或P）的N端（L1和K2）与十二烷基硫酸钠胶束表面结合，启动复合物形成。两亲性P构象的LL-14相对于P构象结合更快且更深地埋入十二烷基硫酸钠胶束中。增加氯化钠浓度会通过屏蔽相互作用伙伴的整体电荷而逐渐延迟LL-14：胶束的结合。由于静电原因，LL-14与十二烷基硫酸钠胶束的结合相对于两性离子二甲基辛酰基磷脂酰胆碱胶束显著更快。低盐离子浓度的阳离子α-螺旋两亲性肽（带正电荷的N端）似乎是更快结合十二烷基硫酸钠的理想选择。
