The overall goals of this proposal are (1) investigate the structure and topology of the membrane-bound KCNE1 protein;(2) elucidate the binding mechanism of KCNE1 with the C-terminal domain of the KCNQ1 K+ channel;(3) identify structural/binding differences in disease-causing long QT syndrome (LQTS) E1 and Q1 mutations, and (4) develop new magnetic resonance techniques to study the structure of membrane proteins. The membrane-bound KCNE1 protein modulates the activity of the KCNQ1 voltage-gated K+ channel. KCNE1 is responsible for slowing the voltage-stimulated activation of KCNQ1 (IKs) and is essential for proper channel and heart function. Hereditary E1/Q1 mutations have been linked to LQTS, atrial fibrillation, sudden infant death syndrome, and deafness. A recently published solution NMR structure of KCNE1 in LMPG micelles reveals that KCNE1 adopts a unique curved alpha-helical secondary structure. Several structural biology studies have indicated that the structure of a protein in a micelle can change dramatically when the protein is embedded in a membrane. Recent CD data by the Lorigan lab on KCNE1 in proteoliposomes reveals dramatic changes in the secondary structure when compared to the micelle structure. We hypothesize that the structure of KCNE1 in a lipid bilayer differs from the solution NMR structure of KCNE1 in LMPG micelles. The three-dimensional structure of KCNQ1 or the KCNE1/KCNQ1 complex has not been determined. Furthermore, the structural nature of the binding interaction of E1 with Q1 is poorly understood and has only been investigated indirectly with biochemical binding and cross-linking assays. It is critical to study the structureof E1 with Q1 to properly describe the function and rhythm of a heartbeat. EPR spectroscopy will be used to directly probe the structural and dynamic properties of KCNE1 and the KCNE1/KCNQ1 complex. Transformative biophysical techniques will be developed to study the structural and dynamic properties of KCNE1 and the KCNE1/KCNQ1 complex in a membrane. These state-of-the-art pulsed EPR spectroscopic techniques will move the field forward by dramatically increasing sensitivity and distance measurements of membrane protein systems such as KCNE1. The following pertinent biological questions will be addressed in the specific aims: Which segments of KCNE1 are helical in a bilayer? Does KCNE1 have a curved or straight ?-helix in a lipid bilayer (which structural model is correct)? What is the structural topology of KCNE1 with respect to the membrane? How does KCNE1 bind to the cytoplasmic domain of the KCNQ1 K+ channel? Which proposed structural model is correct for the E1/Q1 complex? Do disease-causing E1 or Q1 LQTS mutations alter the structure or binding mechanism of the E1/Q1 complex?!

Public Health Relevance

The NIH has recognized the importance of studying the structural properties of integral membrane proteins with PA-10-228. This program announcement has specifically requested for new biophysical techniques to probe the structures of membrane proteins. In accordance with this program announcement, we will develop new EPR spectroscopic methods to probe the structures of integral membranes. The overall goals of this proposal are (1) investigate the structure and topology of the membrane-bound membrane KCNE1;(2) elucidate the binding mechanism of KCNE1 with the C-terminal domain of the KCNQ1 K+ channel;(3) identify structural/binding differences in disease-causing long QT syndrome (LQTS) E1 and Q1 mutations, and (4) develop new magnetic resonance techniques to study the structure of membrane proteins.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM108026-01
Application #
8581509
Study Section
Special Emphasis Panel (ZRG1-BCMB-B (02))
Program Officer
Chin, Jean
Project Start
2013-09-01
Project End
2017-04-30
Budget Start
2013-09-01
Budget End
2014-04-30
Support Year
1
Fiscal Year
2013
Total Cost
$269,800
Indirect Cost
$79,800
Name
Miami University Oxford
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
041065129
City
Oxford
State
OH
Country
United States
Zip Code
45056
Sahu, Indra D; Lorigan, Gary A (2018) Site-Directed Spin Labeling EPR for Studying Membrane Proteins. Biomed Res Int 2018:3248289
Bottorf, Lauren; Sahu, Indra D; McCarrick, Robert M et al. (2018) Utilization of 13C-labeled amino acids to probe the ?-helical local secondary structure of a membrane peptide using electron spin echo envelope modulation (ESEEM) spectroscopy. Biochim Biophys Acta Biomembr 1860:1447-1451
Zhang, Rongfu; Sahu, Indra D; Comer, Raven G et al. (2017) Probing the interaction of the potassium channel modulating KCNE1 in lipid bilayers via solid-state NMR spectroscopy. Magn Reson Chem 55:754-758
Sahu, Indra D; Zhang, Rongfu; Dunagan, Megan M et al. (2017) Characterization of KCNE1 inside Lipodisq Nanoparticles for EPR Spectroscopic Studies of Membrane Proteins. J Phys Chem B 121:5312-5321
Sahu, Indra D; Mayo, Daniel J; Subbaraman, Nidhi et al. (2017) Probing topology and dynamics of the second transmembrane domain (M2?) of the acetyl choline receptor using magnetically aligned lipid bilayers (bicelles) and EPR spectroscopy. Chem Phys Lipids 206:9-15
Zhang, Rongfu; Sahu, Indra D; Bali, Avnika P et al. (2017) Characterization of the structure of lipodisq nanoparticles in the presence of KCNE1 by dynamic light scattering and transmission electron microscopy. Chem Phys Lipids 203:19-23
Herneisen, Alice L; Sahu, Indra D; McCarrick, Robert M et al. (2017) A Budding-Defective M2 Mutant Exhibits Reduced Membrane Interaction, Insensitivity to Cholesterol, and Perturbed Interdomain Coupling. Biochemistry 56:5955-5963
Craig, Andrew F; Clark, Emily E; Sahu, Indra D et al. (2016) Tuning the size of styrene-maleic acid copolymer-lipid nanoparticles (SMALPs) using RAFT polymerization for biophysical studies. Biochim Biophys Acta 1858:2931-2939
Liu, Lishan; Sahu, Indra D; McCarrick, Robert M et al. (2016) Probing the Secondary Structure of Membrane Peptides Using (2)H-Labeled d(10)-Leucine via Site-Directed Spin-Labeling and Electron Spin Echo Envelope Modulation Spectroscopy. J Phys Chem B 120:633-40
Sahu, Indra D; Craig, Andrew F; Dunagan, Megan M et al. (2015) Probing Structural Dynamics and Topology of the KCNE1 Membrane Protein in Lipid Bilayers via Site-Directed Spin Labeling and Electron Paramagnetic Resonance Spectroscopy. Biochemistry 54:6402-12

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