Research Topics - Membrane Biology
Ion permeation in K channels

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Biological cells, in particular neurons, maintain an inside-outside voltage gradient through active transport of ions (Na+, K+, Cl-, and others) across their membranes. The flow of the ions down their gradients through membrane channels is highly selective for each ion. The high selectivity permits nerve cells to signal each other through voltage spikes, which are produced through transient changes of channel conductivities for Na+ ions (channels open and close in about a ms) and K+ ions (channels open and close in about 10 ms). Crucial for the generation of voltage spikes is the selective, yet quick, conduction of ions, but as one knows from personal experience at border crossings, high selectivity and quick crossing seem to be mutually exclusive. Yet biological ion channels reconcile selectivity and speed. Prior experimental work, primarily that of year 2003 Nobelist MacKinnon, as well as computational work suggested how potassium channels achieve selectivity and speed. But until recently no high resolution atomic structure of a potassium channel was known in the open form and the suggested mechanism could not be tested under natural conditions through atomic level simulations. Last year's solution of the structure of the potassium channel Kv1.2 in its open form made it finally possible to simulate, using NAMD, the conduction of ions through Kv1.2 driven by a voltage gradient. The results reported recently confirmed indeed the high selectivity - high speed mechanism suggested earlier, namely a billiard-type motion of two and three ions, the last ion kicking the first ion out. The simulations revealed for the first time, through movies, the overall permeation process, including the jumps of ions between energetically favorable binding sites and the sequence of multi-ion configurations involved in permeation. More on our potassium channel web site.

All Spotlights

Papers

A highly tilted membrane configuration for the pre-fusion state of synaptobrevin. Andrew E. Blanchard, Mark J. Arcario, Klaus Schulten, and Emad Tajkhorshid. Biophysical Journal, 2014. In Press.

Synaptotagmin's role in neurotransmitter release likely involves Ca2+-induced conformational transition. Zhe Wu and Klaus Schulten. Biophysical Journal, 107:1156-1166, 2014.

A structural model of the active ribosome-bound membrane protein insertase YidC. Stephan Wickles, Abhishek Singharoy, Jessica Andreani, Stefan Seemayer, Lukas Bischoff, Otto Berninghausen, Johannes Soeding, Klaus Schulten, Eli van der Sluis, and Roland Beckmann. eLife, 3:e03035, 2014. (17 pages).

Integration of energy and electron transfer processes in the photosynthetic membrane of Rhodobacter sphaeroides. Michaël L. Cartron, John D. Olsen, Melih Sener, Philip J. Jackson, Amanda A. Brindley, Pu Qian, Mark J. Dickman, Graham J. Leggett, Klaus Schulten, and C. Neil Hunter. Biochimica et Biophysica Acta - Bioenergetics, 1837:1769-1780, 2014.

Structural mechanism of voltage-dependent gating in an isolated voltage-sensing domain. Qufei Li, Sherry Wanderling, Marcin Paduch, David Medovoy, Abhishek Singharoy, Ryan McGreevy, Carlos Villalba-Galea, Raymond E. Hulse, Benoit Roux, Klaus Schulten, Anthony Kossiakoff, and Eduardo Perozo. Nature Structural & Molecular Biology, 21:244-252, 2014.

The mechanism of ubihydroquinone oxidation at the Qo-site of the cytochrome bc1 complex. Antony R. Crofts, Sangjin Hong, Charles Wilson, Rodney Burton, Doreen Victoria, Chris Harrison, and Klaus Schulten. Biochimica et Biophysica Acta, 1827:1362-1377, 2013.

Reconciling the roles of kinetic and thermodynamic factors in membrane-protein insertion. James C. Gumbart, Ivan Teo, Benoit Roux, and Klaus Schulten. Journal of the American Chemical Society, 135:2291-2297, 2013.

The p7 protein of hepatitis C virus forms structurally plastic, minimalist ion channels. Danielle E. Chandler, Francois Penin, Klaus Schulten, and Christophe Chipot. PLoS Computational Biology, 8:e1002702, 2012.

Molecular dynamics investigation of the w current in the Kv1.2 voltage sensor domains. Fatemeh Khalili-Araghi, Emad Tajkhorshid, Benoit Roux, and Klaus Schulten. Biophysical Journal, 102:258-267, 2012.

Viewpoint: An emerging consensus on voltage-dependent gating from computational modeling and molecular dynamics simulations. Ernesto Vargas, Vladimir Yarov-Yarovoy, Fatemeh Khalili-Araghi, William A. Catterall, Michael L. Klein, Mounir Tarek, Erik Lindahl, Klaus Schulten, Eduardo Perozo, Francisco Bezanilla, and Benoît Roux. Journal of General Physiology, 140:587-594, 2012.