Intermediate state trapping of a voltage sensor

TY - JOUR

T1 - Intermediate state trapping of a voltage sensor

AU - Lacroix, Jérôme J

AU - Pless, Stephan Alexander

AU - Maragliano, Luca

AU - Campos, Fabiana V

AU - Galpin, Jason D

AU - Ahern, Christopher A

AU - Roux, Benoît

AU - Bezanilla, Francisco

PY - 2012/12

Y1 - 2012/12

N2 - Voltage sensor domains (VSDs) regulate ion channels and enzymes by undergoing conformational changes depending on membrane electrical signals. The molecular mechanisms underlying the VSD transitions are not fully understood. Here, we show that some mutations of I241 in the S1 segment of the Shaker Kv channel positively shift the voltage dependence of the VSD movement and alter the functional coupling between VSD and pore domains. Among the I241 mutants, I241W immobilized the VSD movement during activation and deactivation, approximately halfway between the resting and active states, and drastically shifted the voltage activation of the ionic conductance. This phenotype, which is consistent with a stabilization of an intermediate VSD conformation by the I241W mutation, was diminished by the charge-conserving R2K mutation but not by the charge-neutralizing R2Q mutation. Interestingly, most of these effects were reproduced by the F244W mutation located one helical turn above I241. Electrophysiology recordings using nonnatural indole derivatives ruled out the involvement of cation-II interactions for the effects of the Trp inserted at positions I241 and F244 on the channel's conductance, but showed that the indole nitrogen was important for the I241W phenotype. Insight into the molecular mechanisms responsible for the stabilization of the intermediate state were investigated by creating in silico the mutations I241W, I241W/R2K, and F244W in intermediate conformations obtained from a computational VSD transition pathway determined using the string method. The experimental results and computational analysis suggest that the phenotype of I241W may originate in the formation of a hydrogen bond between the indole nitrogen atom and the backbone carbonyl of R2. This work provides new information on intermediate states in voltage-gated ion channels with an approach that produces minimum chemical perturbation.

AB - Voltage sensor domains (VSDs) regulate ion channels and enzymes by undergoing conformational changes depending on membrane electrical signals. The molecular mechanisms underlying the VSD transitions are not fully understood. Here, we show that some mutations of I241 in the S1 segment of the Shaker Kv channel positively shift the voltage dependence of the VSD movement and alter the functional coupling between VSD and pore domains. Among the I241 mutants, I241W immobilized the VSD movement during activation and deactivation, approximately halfway between the resting and active states, and drastically shifted the voltage activation of the ionic conductance. This phenotype, which is consistent with a stabilization of an intermediate VSD conformation by the I241W mutation, was diminished by the charge-conserving R2K mutation but not by the charge-neutralizing R2Q mutation. Interestingly, most of these effects were reproduced by the F244W mutation located one helical turn above I241. Electrophysiology recordings using nonnatural indole derivatives ruled out the involvement of cation-II interactions for the effects of the Trp inserted at positions I241 and F244 on the channel's conductance, but showed that the indole nitrogen was important for the I241W phenotype. Insight into the molecular mechanisms responsible for the stabilization of the intermediate state were investigated by creating in silico the mutations I241W, I241W/R2K, and F244W in intermediate conformations obtained from a computational VSD transition pathway determined using the string method. The experimental results and computational analysis suggest that the phenotype of I241W may originate in the formation of a hydrogen bond between the indole nitrogen atom and the backbone carbonyl of R2. This work provides new information on intermediate states in voltage-gated ion channels with an approach that produces minimum chemical perturbation.

KW - Amino Acid Sequence

KW - Animals

KW - Hydrogen Bonding

KW - Ion Channel Gating

KW - Ion Channels

KW - Molecular Sequence Data

KW - Mutation

KW - Nitrogen

KW - Oocytes

KW - Protein Conformation

KW - Shaker Superfamily of Potassium Channels

KW - Xenopus

U2 - 10.1085/jgp.201210827

DO - 10.1085/jgp.201210827

M3 - Journal article

C2 - 23183699

SN - 0022-1295

VL - 140

SP - 635

EP - 652

JO - Journal of General Physiology

JF - Journal of General Physiology

IS - 6

ER -