The mobility of single-file water molecules is governed by the number of H-bonds they may form with channel-lining residues.
basic_science · Level V
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- Record sourced from PubMed, PMID 26167541.
- Also identified by PMC identifier 4496530.
- Licence recorded as CC BY-NC.
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Abstract
Channel geometry governs the unitary osmotic water channel permeability, <i>p</i><sub>f</sub>, according to classical hydrodynamics. Yet, <i>p</i><sub>f</sub> varies by several orders of magnitude for membrane channels with a constriction zone that is one water molecule in width and four to eight molecules in length. We show that both the <i>p</i><sub>f</sub> of those channels and the diffusion coefficient of the single-file waters within them are determined by the number <i>N</i><sub>H</sub> of residues in the channel wall that may form a hydrogen bond with the single-file waters. The logarithmic dependence of water diffusivity on <i>N</i><sub>H</sub> is in line with the multiplicity of binding options at higher <i>N</i><sub>H</sub> densities. We obtained high-precision <i>p</i><sub>f</sub> values by (i) having measured the abundance of the reconstituted aquaporins in the vesicular membrane via fluorescence correlation spectroscopy and via high-speed atomic force microscopy, and (ii) having acquired the vesicular water efflux from scattered light intensities via our new adaptation of the Rayleigh-Gans-Debye equation.