Effect of phosphatidylcholine bilayer thickness and molecular order on the binding of the antimicrobial peptide maculatin 1.1

Abstract

Antimicrobial peptides (AMPs) interact directly with bacterial membrane lipids. Thus, changes in the lipid composition of bacterial membranes can have profound effects on the activity of AMPs. In order to understand the effect of bilayer thickness and molecular order on the activity of AMPs, the interaction of maculatin 1.1 (Mac1.1) with phosphatidylcholine (PC) model membranes composed of different monounsaturated acyl chain lengths between 14 and 22 carbons was characterised by dual polarisation interferometry (DPI) and 31P and 1H solid-state NMR techniques. The thickness and bilayer order of each PC bilayer showed a linear dependence on the acyl chain length. The binding of Mac1.1 exhibited a biphasic dependency between the amount of bound Mac1.1 and bilayer thickness, whereby the mass of bound peptide increased from C14 to C16 and then decreased from C16 to C22. Significant perturbation of 31P chemical shift anisotropy (CSA) values was only observed for DOPC (C18) and DEPC (C22), respectively. In the case of DEPC, the greater range in CSA indicated different headgroup conformations or environments in the presence of Mac1.1. Overall, the results indicated that there is a significant change in the bilayer order upon binding of Mac1.1 and this change occurred in a co-operative manner at higher concentrations of Mac1.1 with increasing bilayer thickness and order. Overall, an optimum bilayer thickness and lipid order may be required for effective membrane perturbation by Mac1.1 and increasing the bilayer thickness and order may counteract the activity of Mac1.1 and play a role in antimicrobial resistance to AMPs.

Hydrophilic nanoparticles that kill bacteria while sparing mammalian cells reveal the antibiotic role of nanostructures

“…For mammalian cell-mimicking membrane consisting predominantly of lipids with zero intrinsic curvature, we observed two sets of scatterings (Fig. 4a ), one of which (marked by black arrows) is equally spaced at 0.112, 0.223, and 0.335 Å −1 , respectively for all NPPBs, corresponding to a multilamellar structure with a lamellar periodicity of 56 Å, which fits nicely to a DOPG/DOPC bilayer thickness (i.e., ~44 Å 61 , 62 ) plus a hydration layer (i.e., ~12 Å), and is attributed to stacked membranes brought together by the oppositely charged NPPBs adhered in-between the membranes. Given that we know precisely the P4MVP brush sizes, graft density, the nanoparticle sizes (Table 1 ), and the fact that the charge state of P4MVP is independent on pH 39 , the charge density of NPPBs is calculated (i.e., ~10–30/nm 2 depending on the P4MVP graft density and NPPB sizes).…”

pH-triggered pore-forming peptides with strong composition-dependent membrane selectivity

“…These properties can control the activity of peptides. In particular, membrane charge and thickness have been shown to modulate the binding, aggregation, and activity of peptides ( 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ). Here, we seek to understand how these important aspects of lipid composition affect the macromolecular poration activity of the pHD peptides.…”

Expression and purification of the native C‐amidated antimicrobial peptide maculatin 1.1

“…1,11 NMR and in particular solid-state NMR are powerful techniques to understand the self-assembly mechanism of Mac1 into bacterial membranes. 9,33 Isotopically labelled peptides are usually needed to increase sensitivity and alleviate interference from background signals for in-cell NMR experiment. 34 An E. coli-based cell expression system was selected because of its fast growth kinetics to achieve high cell density cultures, low cost and technical simplicity.…”