Voltage gated K+ (Kv) channels couple the flux of K+ to the membrane potential and play key roles in the brain and heart. Mutations in Kv channels can cause severe diseases in humans such as epilepsies and cardiac arrhythmias. There have been major advances in the structure determination of Kv channels. In spite of the structural information available, there are major questions on the functional mechanisms in Kv channels that remain unanswered. Here we investigate the processes of voltage gating and C-type inactivation that regulate the flux of K+ through Kv channels. We use a multidisciplinary approach centered on unnatural amino acid (UAA) mutagenesis in our investigations. UAA mutagenesis is a very powerful method for protein modification, compared to traditional mutagenesis, because it allows a large variety of side chain modifications and also permits the modification of the protein backbone. We use this approach to investigate the role of the main chain H-bonds in the fourth transmembrane helix (TM4) in voltage gating of the Shaker K+ channel and the hyperpolarization activated and cyclic nucleotide gated ion channel HCN (aim 1). We investigate the role of ion binding sites in the selectivity filter of the Shaker channel in C-type inactivation and we complement the functional studies on Shaker with structural studies on the KvAP channel, an archaeal homolog of the Shaker channel (aim 2). We also investigate the mechanism of C-type inactivation in the hERG K+ channel, which has interesting functional differences from C-type inactivation in the Shaker channel and is physiologically critical for normal cardiac function (Aim 3). The research proposed is significant as it provides greater insight into the functional mechanisms of voltage gating and C-type inactivation in Kv channels. The research is also significant as it will provide a general strategy for using UAA mutagenesis to investigate the role of main chain H-bonds and ion binding sites, which are important for function in many families of membrane proteins.

Public Health Relevance

Voltage gated K+ channels (Kv) play important roles in human physiology and, mutations in Kv channels can cause diseases such as epilepsies and cardiac arrhythmias. In this proposal, we use a multidisciplinary approach that includes unnatural amino acid mutagenesis, electrophysiology and crystallography to understand the functional mechanisms that operate in Kv channels. The knowledge gained from this project will be essential in the development of therapeutics that target Kv channels.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
2R01GM087546-10
Application #
9764015
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Nie, Zhongzhen
Project Start
2009-05-01
Project End
2023-08-31
Budget Start
2019-09-01
Budget End
2020-08-31
Support Year
10
Fiscal Year
2019
Total Cost
Indirect Cost
Name
Oregon Health and Science University
Department
Other Basic Sciences
Type
Schools of Medicine
DUNS #
096997515
City
Portland
State
OR
Country
United States
Zip Code
97239
Infield, Daniel T; Matulef, Kimberly; Galpin, Jason D et al. (2018) Main-chain mutagenesis reveals intrahelical coupling in an ion channel voltage-sensor. Nat Commun 9:5055
Riederer, Erika A; Focke, Paul J; Georgieva, Elka R et al. (2018) A facile approach for the in vitro assembly of multimeric membrane transport proteins. Elife 7:
Matulef, Kimberly; Valiyaveetil, Francis I (2018) Patch-Clamp Recordings of the KcsA K+ Channel in Unilamellar Blisters. Methods Mol Biol 1684:181-191
Kratochvil, Huong T; Maj, Micha?; Matulef, Kimberly et al. (2017) Probing the Effects of Gating on the Ion Occupancy of the K+ Channel Selectivity Filter Using Two-Dimensional Infrared Spectroscopy. J Am Chem Soc 139:8837-8845
Valiyaveetil, Francis I (2017) A glimpse into the C-type-inactivated state for a Potassium Channel. Nat Struct Mol Biol 24:787-788
Focke, Paul J; Hein, Christopher; Hoffmann, Beate et al. (2016) Combining in Vitro Folding with Cell Free Protein Synthesis for Membrane Protein Expression. Biochemistry 55:4212-9
Kratochvil, Huong T; Carr, Joshua K; Matulef, Kimberly et al. (2016) Instantaneous ion configurations in the K+ ion channel selectivity filter revealed by 2D IR spectroscopy. Science 353:1040-1044
Matulef, Kimberly; Annen, Alvin W; Nix, Jay C et al. (2016) Individual Ion Binding Sites in the K(+) Channel Play Distinct Roles in C-type Inactivation and in Recovery from Inactivation. Structure 24:750-761
Leisle, Lilia; Valiyaveetil, Francis; Mehl, Ryan A et al. (2015) Incorporation of Non-Canonical Amino Acids. Adv Exp Med Biol 869:119-51
Focke, Paul J; Annen, Alvin W; Valiyaveetil, Francis I (2015) Engineering the glutamate transporter homologue GltPh using protein semisynthesis. Biochemistry 54:1694-702

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