State-dependent electrostatic interactions of S4 arginines with E1 in S2 during Kv7.1 activation
| Autor: | Dick Wu, Mark A. Zaydman, Ali Nekouzadeh, Kelli Delaloye, Jianmin Cui, Yoram Rudy |
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| Rok vydání: | 2010 |
| Předmět: |
Models
Molecular Time Factors Protein Conformation Surface Properties Physiology Stereochemistry Xenopus Molecular Sequence Data Gating Arginine Article Membrane Potentials 03 medical and health sciences 0302 clinical medicine Protein structure Animals Amino Acid Sequence Cysteine Protein maturation 030304 developmental biology Mesylates Membrane potential 0303 health sciences Voltage-gated ion channel Chemistry Cell Membrane Sulfhydryl Reagents Electrostatics Protein Structure Tertiary Transport protein Long QT Syndrome Protein Transport Transmembrane domain KCNQ1 Potassium Channel Mutation Biophysics Ion Channel Gating 030217 neurology & neurosurgery |
| Zdroj: | The Journal of General Physiology |
| ISSN: | 1540-7748 0022-1295 |
| DOI: | 10.1085/jgp.201010408 |
| Popis: | The voltage-sensing domain of voltage-gated channels is comprised of four transmembrane helices (S1–S4), with conserved positively charged residues in S4 moving across the membrane in response to changes in transmembrane voltage. Although it has been shown that positive charges in S4 interact with negative countercharges in S2 and S3 to facilitate protein maturation, how these electrostatic interactions participate in channel gating remains unclear. We studied a mutation in Kv7.1 (also known as KCNQ1 or KvLQT1) channels associated with long QT syndrome (E1K in S2) and found that reversal of the charge at E1 eliminates macroscopic current without inhibiting protein trafficking to the membrane. Pairing E1R with individual charge reversal mutations of arginines in S4 (R1–R4) can restore current, demonstrating that R1–R4 interact with E1. After mutating E1 to cysteine, we probed E1C with charged methanethiosulfonate (MTS) reagents. MTS reagents could not modify E1C in the absence of KCNE1. With KCNE1, (2-sulfonatoethyl) MTS (MTSES)− could modify E1C, but [2-(trimethylammonium)ethyl] MTS (MTSET)+ could not, confirming the presence of a positively charged environment around E1C that allows approach by MTSES− but repels MTSET+. We could change the local electrostatic environment of E1C by making charge reversal and/or neutralization mutations of R1 and R4, such that MTSET+ modified these constructs depending on activation states of the voltage sensor. Our results confirm the interaction between E1 and the fourth arginine in S4 (R4) predicted from open-state crystal structures of Kv channels and reveal an E1–R1 interaction in the resting state. Thus, E1 engages in electrostatic interactions with arginines in S4 sequentially during the gating movement of S4. These electrostatic interactions contribute energetically to voltage-dependent gating and are important in setting the limits for S4 movement. |
| Databáze: | OpenAIRE |
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