2025 AIChE Annual Meeting
(647h) Effect of Cardiolipin on the Binding and Insertion of CM15 Antimicrobial Peptide on Bacterial Inner Membranes
Authors
Sudeep Punnathanam, Indian Institute of Science
K Ganapathy Ayappa, Indian Institute of Science
With growing global concerns of large-scale antimicrobial resistance due to excessive antibiotic use, antimicrobial peptides (AMPs) holds promise for the development of novel therapeutics. AMPs are a part of the innate immune system of a large number of animal species and are generally more resilient to antimicrobial resistance. AMPs target the bacterial inner membrane, which is primarily composed of phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and cardiolipin (CL) lipids. Although the concentration of cardiolipin depends on the bacterial strain, the role of cardiolipin upregulated in extremophiles, in modulating the interactions with AMPs is unknown. CM15 is a positively charged synthetic AMP made from melittin from bee venom and cecropin A from the cecropia moth. It is known to disrupt bacterial membranes, however the mechanism of its action is not well understood. In this study, we use all atom molecular dynamics simulations to examine the influence of cardiolipin concentration on the interaction free energy of CM15 with membranes with varying cardiolipin concentrations (0%, 5%, 30%) using an in-house string-based method. The free energy computations are carried out using two collective variables; the distance of the protein from the phospholipid headgroups and the alpha-RMSD which determines the helical content. We observe that the increased anionic character of the membrane with increasing cardiolipin concentration causes the binding of CM15 to be more favourable. However, there is a large energy barrier for the peptide’s entry into the membrane, proportional to the concentration of the cardiolipin. Our study delineates the free energy landscape associated with membrane binding and helix formation of the CM15 peptide and can be applied to a wide class of proteins to study binding and insertion of AMPs into bacterial membranes.