Mechanical and molecular activation lead to structurally analogous MscL states

The mechanosensitive channel of large conductance MscL gates in response to tension changes in the membrane to allow the exchange of molecules through its pore. Native ligands that bind and modulate MscL are unknown and trapping an activated state has been challenging. Disruption of lipid access to tension-sensitive transmembrane pockets by modification leads to a concerted structural and functional MscL response. However, it is unknown whether there is structural correlation between tension mediated and molecular activation in mechanosensitive channels. Here, we combine HDX mass spectrometry and ESEEM solvent accessibility measurements on MscL, coupled with molecular dynamics under bilayer tension, to investigate the structural changes associated with the two distinctively derived states. Membrane thinning is not sufficient to hydrate the MscL pore, when lipids are trapped in the pockets, under tensions capable to gate the native channel. Tension and molecule stabilised states present analogous MscL structures, suggesting a link between these two distinct activation mechanisms. These findings could hint at synergistic modes of regulation in mechanosensitive ion channels with implications for their multimodality. Significance StatementBacterial mechanosensitive channels are gated by membrane tension and their function is modulated by lipids or molecules binding to tension sensitive domains. Eukaryotic mechanosensitive channels are multimodal and regulated both by tension and molecular triggers. However, whether molecular and tension activation present mechanistic similarities and whether such mechanisms have evolved through converged structural plasticity of a common origin is largely unclear. Here we use the mechanosensitive channel of large conductance MscL and compare its two distinctive gating dynamics by experimental (EPR and HDX-MS) and computational means (MD). We find that these two differently derived states are structurally analogous suggesting links between mechanosensitivity and ligand-gating in the regulation of mechanosensitive channels and with implications for their multimodality.