Change search
ReferencesLink to record
Permanent link

Direct link
The free energy barrier for arginine gating charge translation is altered by mutations in the voltage sensor domain.
KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics. KTH, Centres, Science for Life Laboratory, SciLifeLab.ORCID iD: 0000-0002-7498-7763
Show others and affiliations
2012 (English)In: PLoS ONE, ISSN 1932-6203, Vol. 7, no 10, e45880- p.Article in journal (Refereed) Published
Abstract [en]

The gating of voltage-gated ion channels is controlled by the arginine-rich S4 helix of the voltage-sensor domain moving in response to an external potential. Recent studies have suggested that S4 moves in three to four steps to open the conducting pore, thus visiting several intermediate conformations during gating. However, the exact conformational changes are not known in detail. For instance, it has been suggested that there is a local rotation in the helix corresponding to short segments of a 3-helix moving along S4 during opening and closing. Here, we have explored the energetics of the transition between the fully open state (based on the X-ray structure) and the first intermediate state towards channel closing (C), modeled from experimental constraints. We show that conformations within 3 Å of the X-ray structure are obtained in simulations starting from the C model, and directly observe the previously suggested sliding 3-helix region in S4. Through systematic free energy calculations, we show that the C state is a stable intermediate conformation and determine free energy profiles for moving between the states without constraints. Mutations indicate several residues in a narrow hydrophobic band in the voltage sensor contribute to the barrier between the open and C states, with F233 in the S2 helix having the largest influence. Substitution for smaller amino acids reduces the transition cost, while introduction of a larger ring increases it, largely confirming experimental activation shift results. There is a systematic correlation between the local aromatic ring rotation, the arginine barrier crossing, and the corresponding relative free energy. In particular, it appears to be more advantageous for the F233 side chain to rotate towards the extracellular side when arginines cross the hydrophobic region.

Place, publisher, year, edition, pages
2012. Vol. 7, no 10, e45880- p.
Keyword [en]
Shaker K+ Channel, Nuclear Magnetic-Resonance, Potassium Channel, Solid-State, Sodium-Channels, Resting State, Side-Chains, S4 Segment, Dynamics, Protein
National Category
Biochemistry and Molecular Biology
URN: urn:nbn:se:kth:diva-104738DOI: 10.1371/journal.pone.0045880ISI: 000310050200005ScopusID: 2-s2.0-84867669798OAI: diva2:566860
EU, European Research Council, 209825Swedish Research Council, 2010-5107Swedish e‐Science Research CenterScience for Life Laboratory - a national resource center for high-throughput molecular bioscience

QC 20121112

Available from: 2012-11-09 Created: 2012-11-09 Last updated: 2012-11-26Bibliographically approved
In thesis
1. Voltage sensor activation and modulation in ion channels
Open this publication in new window or tab >>Voltage sensor activation and modulation in ion channels
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Voltage-gated ion channels play fundamental roles in neural excitability, they are for instance responsible for every single heart beat in our bodies, and dysfunctional channels cause disease that can be even lethal. Understanding how the voltage sensor of these channels function is critical for drug design of compounds targeting neuronal excitability.

The opening and closing of the pore in voltage-gated potassium (Kv) channels is caused by the arginine-rich S4 helix of the voltage sensor domain (VSD) moving in response to an external potential. In fact, VSDs are remarkably efficient at turning membrane potential into conformational changes, which likely makes them the smallest existing biological engines. Exactly how this is accomplished is not yet fully known and an area of hot debate, especially due to the lack of structures of the resting and intermediate states along the activation pathway. In this thesis I study how the VSD activation works and show how toxic compounds modulate channel gating through direct interaction with these quite unexplored drug targets.

First, I show that a secondary structure transition from alpha- to 3(10)-helix in the S4 helix is an important part of the gating as this helix type is significantly more favorable compared to the -helix in terms of a lower free energy barrier. Second, I present new models for intermediate states along the whole voltage sensor cycle from closed to open and suggest a new gating model for S4, where it moves as a sliding 3(10)-helix. Interestingly, this 3(10)-helix is formed in the region of the single most conserved residue in Kv channels, the phenylalanine F233. Located in the hydrophobic core, it directly faces S4 and creates a structural barrier for the gating charges. Substituting this residue alters the deactivation free energy barrier and can either facilitate the relaxation of the voltage sensor or increase the free energy barrier, depending on the size of the mutant. These results are confirmed by new experimental data that supports that a rigid ring at the phenylalanine position is the rate-limiting factor for the deactivation gating process, while the activation is unaffected. Finally, we study how the activation can be modulated for pharmaceutical reasons. Neurotoxins such as hanatoxin and stromatoxin push S3b towards S4 helix limiting S4's flexibility. This makes it harder for the VSD to activate and might explain the stronger binding affinities in resting state.

All these results are highly important both for the general topic of biological macromolecules undergoing functionally critical conformational transitions, as well as the particular case of voltage-gated ion channels where understanding of the gating process is probably the key step to explain the effects of mutations or drug interactions.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. xiii, 77 p.
Trita-FYS, ISSN 0280-316X ; 2012:77
activation, deactivation, inactivation, voltage sensor, VSD, gating, Kv1.2-2.1, Shaker, F233, hydrophobic barrier
National Category
Biological Sciences
urn:nbn:se:kth:diva-104742 (URN)978-91-7501-498-2 (ISBN)
Public defence
2012-12-07, FB53, AlbaNova universitetscentrum, Stockholm, 10:00 (English)
Swedish e‐Science Research CenterScience for Life Laboratory - a national resource center for high-throughput molecular bioscience

QC 20121115

Available from: 2012-11-15 Created: 2012-11-09 Last updated: 2013-04-15Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Schwaiger, Christine S.Hess, BerkElinder, FredrikLindahl, Erik
By organisation
Theoretical & Computational BiophysicsScience for Life Laboratory, SciLifeLab
In the same journal
Biochemistry and Molecular Biology

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 27 hits
ReferencesLink to record
Permanent link

Direct link