 Combining both Ec-MscL molecular model and Tb-MscL crystal structure, it is clear that M1 helices in the core of the transmembrane bundle make up the main gate of the mechanosensitive channel.Regularly placed glycine residues on the M1 segments permits tight packing of the five central helices, forming a narrow (~4 Å) hydrophobic constriction.Hydrophobic M2 helices on the periphery of the MscL barrel face the lipid bilayer.