Patch Clamp Characterisaton of the Effect of Cardiolipin on the Bacterial Mechanosensitive Channels of Small (MscS) and Large (MscL) Conductance

Abstract

The bacterial mechanosensitive channels MscS and MscL respond to membrane tension by opening when the bacterium experiences hypoosmotic shock conditions to prevent cell lysis [1]. Environmental factors such as cholesterol [2] and cations/anions [3] also affect the gating behaviour of these channels. We have previously shown that addition of the negatively charged lipid cardiolipin to POPE/POPC membranes cause rapid and flickery behaviour of MscS [4]. Here, in an expanded study to include MscL, we compare the gating kinetics and pressure sensitivitiy of the channels with and without cardiolipin in both azolectin and mixtures of pure lipids DOPE/DOPC. In azolectin liposomes, mixtures of 10% cardiolipin abolish hysteresis of MscS, but MscL remains largely unaffected, indicating it may stabilise the closed state of MscS. Compared to the azolectin, mixtures of DOPE/DOPC abolish the hysteresis gating of MscS even in the absence of cardiolipin and addition of cardiolipin increases the opening and closing thresholds of both MscS and MscL. These results suggest that cardiolipin shows a significant effect on the mechanosensitive gating of both MscS and MscL.