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Water and Gas Transport through Aquaporins (FWF)

FWF Project P23466

1 April 2011 - 31 March 2014

Dozens of papers in high impact journals assign a CO2 transporting function to some of the aquaporin family members. The non-gas-channel portion of the aquaporin containing membranes would have to have a CO2 permeability (PCO2) which is from 200-fold to 1000-fold smaller than PCO2 of lipid bilayers of comparable composition to be physiologically relevant. Yet, the molecular mechanism which might prevent a neutral molecule with a hexadecane:water partition coefficient of ~1 from freely passing biological membranes is unknown. Thus, we will investigate the hypothesis that PCO2 of the mammalian epithelia is decreased by a protein barrier (e.g uroplakin) and/or regulated by carbonic anhydrase. In continuing our search for lipid constituents which may decrease the gas permeability of lipid bilayers, we are going to reconstitute archaeal lipids and extend the study to include the investigation of H2S transport. If archaeal lipids represent a barrier to H2S, the function of aquaporins in thermophilic archae may be resolved. Moreover, we are going to perform the first stoichiometric study of ammonia and ammonium transport through plant aquaporins. Since there is general disagreement between molecular dynamics simulations and experiments in uncovering which single channel water permeability pf is larger, that of orthodox aquaporins or glyceroaquaporins, we will measure the water flux through planar membranes reconstituted with the purified AqpZ, GlpF and AQP1 proteins and simultaneously determine protein abundance by fluorescence correlation spectroscopy. If pf of GlpF is higher, the doubts raised against the applicability of the water models for molecular dynamics simulations in confined geometries do not appear to be justified. Finally, we will test the prediction made by molecular dynamics simulations whereby conserved arginine in the aquaporin pore is susceptible to transmembrane voltage, i.e. we will provide the first experimental test to determine whether human aquaporins are gated.


The mobility of single-file water molecules is governed by the number of H-bonds they may form with channel-lining residues
Andreas Horner, Florian Zocher, Johannes Preiner, Nicole Ollinger, Chistine Siligan, Sergey A. Akimov and Peter Pohl
Sci. Adv. 1, e1400083 (2015).

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High-Speed AFM Images of Thermal Motion Provide Stiffness Map of Interfacial Membrane Protein Moieties
Johannes Preiner, Andreas Horner, Andreas Karner, Nicole Ollinger, Christine Siligan, Peter Pohl, Peter Hinterdorfer.
Nano Letters, Volume: 15, Issue: 1, pp: 759-763, Published: January 2015.

Local Partition Coefficients Govern Solute Permeability of Cholesterol-Containing Membranes
Florian Zocher, David van der Spoel, Peter Pohl and Jochen Hub
Biophysical Journal, 2013 Dec 17;105(12):2760-70.

Monitoring Single Channel Water Permeability in Polarized Cells
L. Erokhova, A. Horner, P. Kügler, and P. Pohl
Journal of Biological Chemistry, Volume 286, Issue 46, pp. 39926-39932. Published: 18 November 2011.

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Uroplakins do not restrict CO2 transport through the urothelium
Florian Zocher, Mark L. Zeidel, Andreas Missner, Tung-Tien Sun, Ge Zhou, Yi Liao, Max von Bodungen, Warren G. Hill, Susan Meyers, Peter Pohl, John C. Mathai
Journal of Biological Chemistry, Volume 287, Issue 14, pp. 11011-11017. Published: 30 March 2012.

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