Ribbons representation of the homoheptameric Mechanosensitive channel of Small conductance (MscS) from Escherichia coli, according to the revised Rees crystal structure (Bass et al., 2002; Steinbacher et al, 2007). MscS contributes to the release of osmolytes in response to increased membrane tension, thereby preventing cellular lysis under hypoosmotic shock. The pore-lining region, which is conserved among MscS family members in bacteria, plants and fungi is indicated in blue ribbons; residues L109 and L105 (yellow spheres) form the narrowest constriction of the permeation pathway. The extreme C-terminal region of the cytoplasmic domain (green ribbons) is proposed to influence ion selectivity, as is a notable charged residue at the top of the permeation pathway R88 (red spheres).
Image selected from: Recent characterizations of MscS and its homologs provide insight into the basis of ion selectivity in mechanosensitive channels by Maksaev and Haswell