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- Title
Structural changes in the mitochondrial Tim23 channel are coupled to the proton-motive force.
- Authors
Malhotra, Ketan; Sathappa, Murugappan; Landin, Judith S; Johnson, Arthur E; Alder, Nathan N
- Abstract
Tim23, the central subunit of the TIM23 protein-translocation complex, forms a voltage-gated channel in the mitochondrial inner membrane (MIM), an energy-conserving membrane that generates a proton-motive force to drive vital processes. Using high-resolution fluorescence mapping of a channel-facing transmembrane segment (TMS2) of Tim23 from Saccharomyces cerevisiae, we demonstrate that changes in the energized state of the MIM cause marked structural alterations in the channel region. In an energized membrane, TMS2 forms a continuous α-helix that is inaccessible to the aqueous intermembrane space (IMS). Upon depolarization, the helical periodicity of TMS2 is disrupted, and the channel becomes exposed to the IMS. Kinetic measurements confirm that changes in TMS2 conformation coincide with depolarization. These results reveal how the energized state of the membrane drives functionally relevant structural dynamics in membrane proteins coupled to processes such as channel gating.
- Subjects
BIOLOGICAL membranes; SACCHAROMYCES cerevisiae; MUON depolarization; MEMBRANE proteins; FLUORESCENCE microscopy; PROTON spectra
- Publication
Nature Structural & Molecular Biology, 2013, Vol 20, Issue 8, p965
- ISSN
1545-9993
- Publication type
Article
- DOI
10.1038/nsmb.2613