Correlation between Single-Molecule Dynamics and Biological Functions of Antimicrobial Peptide Melittin

Abstract

Many fundamental biological processes occur on cell membranes, and a typical example is the membrane permeabilization by peptides for an antimicrobial purpose. Previous studies of the underlying mechanism mostly focus on structural changes of membranes and peptides during their interactions. Herein, from a new perspective of single-molecule dynamics, the real-time three-dimensional motions of individual phospholipid and peptide molecules were monitored, and specifically, their correlation with the membrane poration function of melittin, a most representative natural antimicrobial peptide, was studied. We found that the adsorption and accumulation of melittin on the membrane surface significantly sped up the lateral diffusion of lipids surrounding the peptides, which in turn facilitated the peptide insertion at such heterogeneous regions. A unique "U"-bending pathway of melittin during membrane insertion and the ultimate formation of toroidal pores with dynamical translocations of peptides and lipids with several metastable states between the two leaflets of bilayer were observed.

Real-time monitoring the staged interactions between cationic surfactants and a phospholipid bilayer membrane

“…After that, a high-quality SLB was formed. 32 The silicon-supported SPB was immediately moved to and installed in the photo-voltage test system and worked as a working electrode in the following tests (with a working area of 15 Â 10 mm 2 ). Before each test, the voltage pulses under light illumination of electrodes immersed in deionized water were recorded first, as a baseline for the following in situ test.…”

“…This phenomenon is similar as that of many antimicrobial peptides (e.g., melittin, PGLa and Magainin) at low concentrations. 29,32 In brief, photovoltage and GUV leakage tests showed that, at low concentrations (e.g., 1-10 mM), TTAB produced an obvious while concentrationdependent permeabilization effect on the phospholipid membrane which reached equilibrium within minutes; however, this effect became complicated (e.g., at 10 mM) due to the coexistence of many competitive processes.…”

Cholesterols Work as a Molecular Regulator of the Antimicrobial Peptide-Membrane Interactions

“…For Mel, its crystal structure was taken from the protein data bank (PDB ID: 2MLT). Specifically, chain A, which has a more flexible structure and consequently an improved membrane activity, was chosen (Irudayam and Berkowitz, 2012;Lyu et al, 2017;Deng et al, 2019;Xu et al, 2020). Then the peptide was coarse-grained using the Martinize script with MARTINI force field (version 2.2) (de Jong et al, 2013;Deng et al, 2019;Marrink et al, 2007).…”

“…As a result of the complicated Mel-lipid interactions, to form transmembrane pores is a premise of the function realization of Mel (Hong et al, 2019;Lee et al, 2013;Krauson et al, 2012). Such an interaction process generally obeys the two-state model, including the binding and accumulation of peptides on membrane surface and the subsequent transmembrane insertion of peptides for pore formation (Huang, 2000;Lee et al, 2013;Xu et al, 2020). This process is influenced by many factors especially the peptide concentration, i.e., the peptide-to-lipid ratio, P/L (Hong et al, 2019).…”

“…Once the P/L ratio is above a threshold value (e.g., P/L 1/43), some peptides accumulate together and corporately reorient themselves to achieve membrane insertion which finally cause pore formation (Lee et al, 2013). Furthermore, transition of peptides from the membrane surface-binding state to transmembrane-inserting state is accompanied with the changes in lipid packing states (e.g., membrane thinning and stretching) (Hong et al, 2019;Lee et al, 2013;Liu et al, 2018;Xu et al, 2020). In general, the membrane poration behavior is crucial for Mel to kill bacteria, which is a result of the complicated interplay between peptides and lipids.…”