Structural biology: A channel with a twist
Mechanosensitive channels release tension in cell membranes by opening 'pressure relief' pores. The structure of a partially open channel suggests a gating mechanism and delivers an unexpected architectural twist. Mechanosensitive channels protect bacteria from osmotic shock by allowing ions to flow across the membrane in response to changes in membrane tension. MscL is one such channel with large conductance, which exhibits several intermediate states between its closed and open forms. The 3.8-Å crystal structure of the Staphylococcus aureus MscL has now been determined in a nonconductive, partially expanded and tetrameric form.