Desformylgramicidin: A model channel with an extremely high water permeability
by Saparov, S. M.; Antonenko, Y. N.; Koeppe, R. E.; Pohl, P.
The water conductivity of desformylgramicidin exceeds the permeability of gramicidin A by two orders of magnitude. With respect to its single channel hydraulic permeability coefficient of 1.1.10(-12) cm(3) s(-1), desformylgramicidin may serve as a model for extremely permeable aquaporin water channel proteins (AQP4 and AQPZ). This osmotic permeability exceeds the conductivity that is predicted by the theory of single-file transport. It was derived from the concentration distributions of both pore-impermeable and -permeable cations that were simultaneously measured by double barreled microelectrodes in the immediate vicinity of a planar bilayer. From solvent drag experiments, approximately five water molecules were found to be transported by a single-file process along with one ion through the channel. The single channel proton, potassium, and sodium conductivities were determined to be equal to 17 pS (pH 2.5), 7 and 3 pS, respectively. Under any conditions, the desformyl-channel remains at least 10 times longer in its open state than gramicidin A.
- Journal
- Biophysical Journal
- Volume
- 79
- Issue
- 5
- Year
- 2000
- Start Page
- 2526-2534
- URL
- https://dx.doi.org/10.1016/s0006-3495(00)76493-9
- ISBN/ISSN
- 1542-0086; 0006-3495
- DOI
- 10.1016/s0006-3495(00)76493-9