H-bond formation governs the unitary water permeability of narrow channels
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8th ÖGMBT Annual Meeting 2016 - Life Sciences for the Next Generation
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According to classical hydrodynamics, channel geometry determines the unitary osmotic water permeability, pf. This is at odds with the observation that pf of narrow transmembrane channels may vary by several orders of magnitude even though they all are only one water molecule wide and roughly equal in length. We show that the number of poor-lining residues NH which may donate or accept hydrogen bonds determine pf of those channels1. Water diffusivity depends logarithmic on NH, which is in line with the multiplicity of binding options at higher NH densities. We obtained high-precision pf values by a combination of (i) counting the number of reconstituted aquaporins in large unilamellar vesicles via fluorescence correlation spectroscopy2,3 and high-speed atomic force microscopy, and (ii) acquiring the vesicular water efflux from scattered light intensities via our new adaptation of the Rayleigh-Gans- Debye equation1,4.
1. Horner, A. et al. The mobility of single-file water molecules is governed by the number of H-bonds they may form with channel-lining residues. Sci. Adv. 1, 1?5 (2015).
2. Knyazev, D. G. et al. The bacterial translocon secYEG opens upon ribosome binding. J. Biol. Chem. 288, 17941?17946 (2013).
3. Hoomann, T., Jahnke, N., Horner, A., Keller, S. & Pohl, P. Filter gate closure inhibits ion but not water transport through potassium channels. Proc. Natl. Acad. Sci. U. S. A. 110, 10842?7 (2013).
4. Erokhova, L., Horner, A., Ollinger, N., Siligan, C. & Pohl, P. The Sodium Glucose Cotransporter SGLT1 is an Extremely Efficient Facilitator of Passive Water Transport. J. Biol. Chem. 291, jbc.M115.706986 (2016).
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