Comparisons of the SF regions. (Left and middle columns) Views from the extracellular surface showing the size of the SF central holes, defined as the white areas in the middle of each structure. (Right column) Side view superpositions of the SFs in cartoon and stick depictions, in each case comparing the Open_Ms structure (light green) with the corresponding structure in that row. The identities of the SF residues (TLES) are indicated. Only two monomers are shown for clarity. (A; left) Open_Ms (pale green) and (middle) pOpen_Ms (turquoise) structures. (B; middle) Closed_Ab (slate) and overlay (right) comparison of Closed_Ab and Open_Ms. (C) As in B for Inactivated_Ab (AB tetramer; gray). (D) As in B for Inactivated_Ab (CD tetramer; gray). (E) As in B for Closed_Ae (raspberry). The distances between the narrowest parts of the SFs in each case are given in Table S1.