Open-channel structure. The symmetrized open-channel model obtained from the simulations conducted with 60 mN/m of tension are shown, viewed from in the plane of the membrane (A) and just the TM helices from above the membrane (B), with one subunit highlighted for clarity. The location of TM1 in the closed-state crystal structure is shown in gray. Comparisons with previous open-channel models are shown viewed from in (C) and above (D) the plane of the membrane. In these, TM1 and TM2 of just one subunit of the closed structure (gray), our open-state model (blue), and the models of Meyer (2007) (green) and Sukharev et al. (2001b) (red) are shown. The location of the pore axis is marked by the black line. Comparisons of the positions of TM1 (E) and TM2 (F) in our open-state model and the hypothesized intermediate SaMscL structure (purple). TM1 of all five subunits of the closed structure is shown in D–F for clarity.