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- Title
Electrostatic couplings in OmpA ion-channel gating suggest a mechanism for pore opening.
- Authors
Hong, Heedeok; Szabo, Gabor; Tamm, Lukas K.
- Abstract
The molecular forces that drive structural transitions between the open and closed states of channels and transporters are not well understood. The gate of the OmpA channel is formed by the central Glu52-Arg138 salt bridge, which can open to form alternate ion pairs with Lys82 and Glu128. To gain deeper insight into the channel-opening mechanism, we measured interaction energies between the relevant side chains by double-mutant cycle analysis and correlated these with the channel activities of corresponding point mutants. The closed central salt bridge has a strong interaction energy of −5.6 kcal mol−1, which can be broken by forming the open-state salt bridge Glu52-Lys82 (ΔΔGInter = −3.5 kcal mol−1) and a weak interaction between Arg138 and Glu128 (ΔΔGInter = −0.6 kcal mol−1). A covalent disulfide bond in place of the central salt bridge completely blocks the channel. Growth assays indicate that this gating mechanism could physiologically contribute to the osmoprotection of Escherichia coli cells from environmental stress.
- Subjects
ELECTROSTATIC adhesion; MEMBRANE proteins; ION channels; PROTEIN-protein interactions; LIGAND binding (Biochemistry); OSMOREGULATION; MICROBIOLOGICAL assay; GROWTH
- Publication
Nature Chemical Biology, 2006, Vol 2, Issue 11, p627
- ISSN
1552-4450
- Publication type
Article
- DOI
10.1038/nchembio827