期刊
NATURE CHEMICAL BIOLOGY
卷 2, 期 11, 页码 627-635出版社
NATURE PUBLISHING GROUP
DOI: 10.1038/nchembio827
关键词
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资金
- NIGMS NIH HHS [GM51329, R01 GM051329] Funding Source: Medline
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 (Delta Delta G(Inter) -3.5 kcal mol(-1)) and a weak interaction between Arg138 and Glu128 (Delta Delta G(Inter) = -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.
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