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Hydration of Conduction Pores in KcsA Potassium Channel and M2 Proton Channel



J L. Blasic, David L. Worcester, Klaus Gawrisch, Philip A. Gurnev, Mihaela Mihailescu


Water-filled hydrophobic cavities of channel proteins serve as gateways for transfer of ions across membrane. However, functional implications of hydration-dehydration transitions remain elusive due to difficulties to detect and quantify water in channel cavities. Here we employ neutron diffraction to determine water distributions in two tetrameric channels embedded in lipid bilayers: potassium channel KcsA and trans-membrane domain of M2 protein of Influenza A virus. We show that for the KcsA channel in the closed state, the distribution of water is peaked in the middle of the membrane, showing water in the central cavity. This water is displaced by the channel blocker tetrabutyl-ammonium. We quantify amounts of water associated with the channel, using neutron diffraction and solid-state NMR. In contrast, the M2 proton channel shows a "V"- shaped water profile across the membrane, with a narrow constriction at the center, like the hour-glass shape of its internal surface.
Journal of Biological Chemistry


lipid bilayer, neutron diffraction, ion channels, KcsA, M2


Blasic, J. , Duewer, D. , Gawrisch, K. , , P. and Mihailescu, M. (2015), Hydration of Conduction Pores in KcsA Potassium Channel and M2 Proton Channel, Journal of Biological Chemistry, [online], (Accessed April 21, 2024)
Created September 14, 2015, Updated November 10, 2018