Figure 1.

(a) Superposition of EcMscS DDM (green) and HpMscS DDM (blue), with one subunit highlighted from each heptamer, including the representation of the transmembrane (TM) helices as cylinders. The principal differences between these structures occur in the positioning of the transmembrane helices TM1, TM2, and TM3a, while TM3b and the cytoplasmic domain are similar in both structures. This figure was created using Chimera.³⁵ (b) Protein sequence alignment of EcMscS and HpMscS emphasizing the transmembrane organization, with TM1 highlighted in blue, TM2 highlighted in green, and the two sections of TM3 (TM3a and TM3b) highlighted in yellow. The red stars and the red circle denote the pore blocking residues (Leucines 105 and 109 in EcMscS) and the hinge position (Gly113) in TM3, respectively. The sequence alignment was performed using TCoffee³⁶ and the sequence display output using multiple align show.³⁷ [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]