BPS2026 – Understanding the role of F127 in MscS gating

Bacteria frequently encounter changes in their environment; changes in the osmolatity of their environment can lead to cell death. Bacteria rely on mechanosensitive ion channels to rapidly adapt to sudden osmotic downshock, releasing solutes to prevent lysis. These channels gate in response to tension across the membrane ensuring cell survival in response to osmotic downshock. Bacterial mechanosensitive ion channels E . coli membranes contain seven unique mechanosensitive ion channels: MscL, MscS, MscK, MscM, YnaI, YbdG, and YbiO. Of these channels, MscS and MscL are the most well-studied. MscS, the mechanosensitive channel of small conductance, gates at a lower pressure threshold than MscL. MscS springs into the open state upon the application of lateral pressure to the membrane. Previously, we demonstrated that when F127 is mutated to a positive, negative, or neutral residue, alterations to the open state stability and kinetics were observed. These mutations showed limited alterations to the gating threshold of the channel, suggesting that their role in MscS gating occurs once the channel achieves the open state. Here, we expand on the previous work to determine the role of F127 within the gating cycle of MscS through additional point mutations. Our analysis suggests that F127 interacts with the pocket lipids as the channel reaches the open state.