Voltage-gated channels are membrane proteins that contain three crucial structural elements: an ion conduction pore domain (PD) that can distinguish K+ from Na+ and Ca2+ ions;a gate within the PD that minimizes the flow of ions in the closed state;and voltage-sensing domains (VSD) that detect changes in membrane voltage and trigger opening and closing of the gate. A fundamental experimental problem is the difficulty of capturing critical atomic details of VSDs in membranes by crystallography. This program project (Stephen White, Director) is designed to obtain critical structural information about VSDs in fluid lipid bilayers through the concerted use of specific deuteration, neutron diffraction, neutron reflectivity, and molecular dynamics simulations. The Program consists of six closely interlocked Projects and an important collaboration: Core A. Administrative Core. Stephen White, PI. This core provides administrative support for the entire Program. Core B. Neutron Scattering Core. Stephen White, PI. The neutron Core provides technical and training support for neutron diffraction/reflectivity measurements that will be carried out at the NIST Center for Neutron Research. Core C. Organic Synthesis Core, Richard Chamberlin, PI. The Organic Synthesis Core will provide novel specifically deuterated compounds, such as lipids and amino acids, and will carry out semi-syntheses of VSDs and channels. It will be located at UC Irvine. Project 1. Molecular Dynamics Simulations of Channels and Voltage Sensor Domains. Douglas Tobias, PI. Located at UC Irvine, this project is devoted to MD simulations that underlie-and inspire-most of the experimental work in projects 2 and 3. Project 2. Neutron Diffraction Studies of Voltage Sensor Molecules in Lipid Bilayers. Stephen White, PI. The experiments are directed toward a structural understanding of the interactions of the KvAP VSD in bilayers, the interaction of the KvAP S4 helix with lipids in multilamellar bilayers, and the disposition of the VSD-blocking toxin VSTxl toxin in bilayers. Project 3. Structural Studies of Voltage-Gated Potassium Channels as a Function of Transmembrane Electrochemical Potential. J. Kent Blasie, PI. Located at the University of Pennsylvania, this project is directed toward incorporating VSDs and whole potassium channels into single, tethered lipid bilayers and to observe by time-resolved x-ray reflectivity and neutron reflectivity structural changes in the sensors and channels induced by transmembrane electrochemical potentials. Collaboration. Potassium Channel Biophysics. Kenton Swartz, PI. Dr. Swartz's laboratory at the NINDS has an influential research program devoted to the mechanism of voltage gated ion channels. His work focuses directly on the molecular basis of voltage sensor domains and their interactions with VSD-blocking toxins.

Public Health Relevance

This Program Project investigates how ion channels gate the flow of ions across nerve, muscle, and cardiac cells in response to changes in voltage across their cell membranes. These voltage changes, called action potentials, are the means by which nerve, muscle, and cardiac cells communicate with each other. Many neuromuscular and cardiac diseases arise from defects in the way action potentials are produced. Results from this Program will help us understand the origin of such diseases.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Program Projects (P01)
Project #
5P01GM086685-04
Application #
8214529
Study Section
Special Emphasis Panel (ZRG1-BCMB-N (40))
Program Officer
Chin, Jean
Project Start
2009-02-06
Project End
2014-01-31
Budget Start
2012-02-01
Budget End
2013-01-31
Support Year
4
Fiscal Year
2012
Total Cost
$1,319,443
Indirect Cost
$356,233
Name
University of California Irvine
Department
Physiology
Type
Schools of Medicine
DUNS #
046705849
City
Irvine
State
CA
Country
United States
Zip Code
92697
Cymer, Florian; von Heijne, Gunnar; White, Stephen H (2015) Mechanisms of integral membrane protein insertion and folding. J Mol Biol 427:999-1022
Andersson, Magnus; Mattle, Daniel; Sitsel, Oleg et al. (2014) Copper-transporting P-type ATPases use a unique ion-release pathway. Nat Struct Mol Biol 21:43-8
Ulmschneider, Martin B; Ulmschneider, Jakob P; Schiller, Nina et al. (2014) Spontaneous transmembrane helix insertion thermodynamically mimics translocon-guided insertion. Nat Commun 5:4863
Tronin, Andrey Y; Nordgren, C Erik; Strzalka, Joseph W et al. (2014) Direct evidence of conformational changes associated with voltage gating in a voltage sensor protein by time-resolved X-ray/neutron interferometry. Langmuir 30:4784-96
Jiang, Xiaoxu; Villafuerte, Maria Katerina R; Andersson, Magnus et al. (2014) Galactoside-binding site in LacY. Biochemistry 53:1536-43
Madrona, Yarrow; Hollingsworth, Scott A; Tripathi, Sarvind et al. (2014) Crystal structure of cindoxin, the P450cin redox partner. Biochemistry 53:1435-46
Andersson, Magnus; Ulmschneider, Jakob P; Ulmschneider, Martin B et al. (2013) Conformational states of melittin at a bilayer interface. Biophys J 104:L12-4
Tronin, A; Chen, C-H; Gupta, S et al. (2013) Structural changes in single membranes in response to an applied transmembrane electric potential revealed by time-resolved neutron/X-ray interferometry. Chem Phys 422:
Reichow, Steve L; Clemens, Daniel M; Freites, J Alfredo et al. (2013) Allosteric mechanism of water-channel gating by Ca2+-calmodulin. Nat Struct Mol Biol 20:1085-92
Kyrychenko, Alexander; Tobias, Douglas J; Ladokhin, Alexey S (2013) Validation of depth-dependent fluorescence quenching in membranes by molecular dynamics simulation of tryptophan octyl ester in POPC bilayer. J Phys Chem B 117:4770-8

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