Mechanosensitive channels as novel targets for antimicrobial agents

[Truncated abstract] MscL, the bacterial Mechanosensitive (MS) channel of large conductance, has become a prototype MS channel for studying structure-function relationships in this class of ion channels. MscL homologues have commonly been found in Gram -ve and Gram +ve strains forming a sub-family of a larger family of MS ion channels encompassing prokaryotes (bacteria and archea) as well as cell-walled eukaryotes (fungi and plants). In addition to being highly conserved, no MscL gene has been found within the human genome making it a desired target. During my honours year, I used in silico modelling to find the binding positions and energies of a number of ligands to MscL. Ligands known to open the channel were the basis of the modelling. The ligands included the triphenylmethane dyes, eriochrome cyanine R and brilliant green, and esters of para-hydroxybenzoic acid in addition to other ligands. From that work I was able to find the binding positions of the ligands and learn about their binding energy profiles throughout the protein pore. I also used a structure based approach for pharmacophore design. Through an iterative feedback, the ligand below, 124(2)CO2, in its ionized form showed unprecedented binding to MscL. The specific aims for this PhD were:- 1. In silico ligand docking, de novo ligand design of the triphenylmethane dyes and of 124(2)CO2 and its analogues, 2. Susceptibility testing and synergy testing of compounds from (1) against a number of microorganisms, and 3. Patch clamp electrophysiology experiments to determine the effect of a number of compounds from (1) on MscL and more specifically determine if the antimicrobial activity of the triphenylmethane dyes is due to opening of the MscL. The current study demonstrates that synergy was observed between eriochrome cyanine R and the 30S inhibitors kanamycin and tobramycin.