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 K(v)1-type potassium channels (Shaker and K(v)1.2/2.1 chimera) through site-directed mutagenesis, electrophysiology, and molecular simulations. The F290L mutation in Shaker (F233L in K(v)1.2/2.1) 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 similar to 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
Elsevier (Cell Press) / Biophysical Society , 2013. Vol. 104, no 1, 75-84 p.
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:liu:diva-88664DOI: 10.1016/j.bpj.2012.11.3827ISI: 000313541200010OAI: oai:DiVA.org:liu-88664DiVA: diva2:605494
Funding Agencies|European Research Council|209825|Swedish Foundation for Strategic Research||Swedish Research Council||Swedish Heart-Lung Foundation||Swedish Brain Foundation||County Council of Ostergotland||Queen Silvias Anniversary Foundation||King Gustaf V and Queen Victorias Freemasons Foundation||Swedish Society for Medical Research||2013-02-142013-02-142014-06-04Bibliographically approved