Defining the Physical Gate of a Mechanosensitive Channel, MscL, by Engineering Metal-Binding Sites

ABSTRACT

The mechanosensitive channel of large conductance, MscL, of Escherichia coli is one of the best-studied mechanosensitive proteins. Although the structure of the closed or "nearly-closed" state of the Mycobacterium tuberculosis ortholog has been solved and mechanisms of gating have been proposed, the transition from the closed to the open states remains controversial. Here, we probe the relative position of specific residues predicted to line the pore of MscL in either the closed state or during the closed-to-open transition by engineering single-site histidine substitutions and assessing the ability of Ni^sup 2+^, Cd^sup 2+^ or Zn^sup 2+^ ions to affect channel activity. …