Ec-MscL consists of five identical subunits, each 136 amino acids long. Each subunit crosses the membrane twice through alpha-helical transmembrane segments, M1 and M2, which are interconnected by an extracellular loop. It forms a homopentameric channel with ten transmembrane spanners. 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. It is important to note that the M1 and M2 helices of the same subunit are not connected; instead, the M1 helix of one subunit makes tight contact with the M2 helix of the adjacent subunit. With additional interactions through a salt bridge in Ec-MscL, the entire complex is secured together.