The conserved phenylalanine in the K+ channel voltage-sensor domain creates a barrier with unidirectional effects
2013 (English)In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 104, no 1, 75-84 p.Article in journal (Refereed) Published
Voltage-gated ion channels are crucial for regulation of electric activity of excitable tissues such as nerve cells, and play important roles in many diseases. During activation, the charged S4 segment in the voltage sensor domain translates across a hydrophobic core forming a barrier for the gating charges. This barrier is critical for channel function, and a conserved phenylalanine in segment S2 has previously been identified to be highly sensitive to substitutions. Here, we have studied the kinetics of Kv1-type potassium channels (Shaker and Kv1.2/2.1 chimera) through site-directed mutagenesis, electrophysiology, and molecular simulations. The F290L mutation in Shaker (F233L in Kv1.2/2.1) accelerates channel closure by at least a factor 50, although opening is unaffected. Free energy profiles with the hydrophobic neighbors of F233 mutated to alanine indicate that the open state with the fourth arginine in S4 above the hydrophobic core is destabilized by ∼17 kJ/mol compared to the first closed intermediate. This significantly lowers the barrier of the first deactivation step, although the last step of activation is unaffected. Simulations of wild-type F233 show that the phenyl ring always rotates toward the extracellular side both for activation and deactivation, which appears to help stabilize a well-defined open state.
Place, publisher, year, edition, pages
2013. Vol. 104, no 1, 75-84 p.
Potassium Channel, Gating Charge, Transition, Kv1.2, State, Conformation, Hanatoxin, Segment, Field, S4
Biochemistry and Molecular Biology
IdentifiersURN: urn:nbn:se:kth:diva-104739DOI: 10.1016/j.bpj.2012.11.3827ISI: 000313541200010ScopusID: 2-s2.0-84872151920OAI: oai:DiVA.org:kth-104739DiVA: diva2:566861
FunderScience for Life Laboratory - a national resource center for high-throughput molecular bioscienceEU, European Research Council, 209825Swedish Foundation for Strategic Research Swedish Research CouncilSwedish e‐Science Research Center
QC 20130212. Updated from manuscript to article in journal.2012-11-092012-11-092013-02-14Bibliographically approved