Voltage-gated cation channels are membrane proteins responsible for the generation &propagation of action potentials central to neurological signal transmission. They are comprised of either four identical subunits (Kchannels) or homologous domains (Na &Ca channels), arranged about the normal to the membrane plane. Each of the four subunits (or domains) is comprised of six transmembrane helices, S1-S4 forming the voltage-sensor domain (VSD) and S5-S6 forming the pore domain (PD). Positively charged residues predominately in the S4 helix are responsible for voltage sensing by the VSD. The structural response of the VSD domain in each of the four subunits (or domains) to depolarizing transmembrane electrochemical potentials responsible for "gating currents" appears to be sequential. The activation of all four VSD's is required for the subsequent concerted opening of the cation pore formed by the four PD's resulting in selective "cation currents". An "electromechanical" coupling is required between the VSD's and the PD's to control the opening of the ion channel pore, otherwise closed at the membrane resting potential. The x-ray crystal structures of two voltage-gated potassium channels have revealed a "modular" structure showing the VSD to be somewhat "loosely associated" with the PD. This modular aspect has complicated attempts to understand the mechanism of the electromechanical coupling, which remains unknown. Crucial direct evidence is missing, namely definitive structural information concerning the nature of structural changes within the VSD and PD as a function of the applied transmembrane electrochemical potential.
The Specific Aims concern the utilization of state-of-the-art techniques throughout to investigate the structures of the intact voltage-gated K-channel, as well as only its voltage-sensor domain, vectorially-oriented within single lipid bilayers as a function of the applied transmembrane electrochemical potential. These techniques include membrane protein semi-synthesis, x-ray &neutron reflectivity, enhanced by interferometry, and computer simulation constrained by the experimental results.

Public Health Relevance

The approach is applicable to all voltage-gated and ligand-gated ion channels central to neurological signal transmission phenomena. It can thereby contribute substantially to our understanding of not only the normal neurological phenomena, but also channelopathy diseases arising from ion channel dysfunction and drug action targeting these channels to modulate these phenomena.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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University of California Irvine
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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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