Abstract
The atomic structure of OmpX, the smallest member of the bacterial outer membrane protein family, has been previously established by X-ray crystallography and NMR spectroscopy. In apparent conflict with electrophysiological studies, the lumen of its transmembrane β-barrel appears too tightly packed with amino acid side chains to let any solute flow through. In the present study, high-resolution solution NMR spectra were obtained of OmpX kept water-soluble by either amphipol A8-35 or the detergent dihexanoylphosphatidylcholine. Hydrogen/deuterium exchange measurements performed after prolonged equilibration show that, whatever the surfactant used, some of the amide protons of the membrane-spanning region exchange much more readily than others, which likely reflects the dynamics of the barrel.
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Acknowledgments
This work was funded by the CNRS, Paris-7 University, and financial support to J.-L.P. by the HFSP Organization (grant RG00223/2000-M) and the Fondation Rothschild.
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Catoire, L.J., Zoonens, M., van Heijenoort, C. et al. Solution NMR mapping of water-accessible residues in the transmembrane β-barrel of OmpX. Eur Biophys J 39, 623–630 (2010). https://doi.org/10.1007/s00249-009-0513-2
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DOI: https://doi.org/10.1007/s00249-009-0513-2