A tyrosine substitution in the cavity wall of a K channel induces an inverted inactivation
2008 (English)In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 94, no 8, 3014-3022 p.Article in journal (Refereed) Published
Ion permeation and gating kinetics of voltage-gated K channels critically depend on the amino-acid composition of the cavity wall. Residue 470 in the Shaker K channel is an isoleucine, making the cavity volume in a closed channel insufficiently large for a hydrated K+ ion. In the cardiac human ether-a-go-go-related gene channel, which exhibits slow activation and fast inactivation, the corresponding residue is tyrosine. To explore the role of a tyrosine at this position in the Shaker channel, we studied I470Y. The activation became slower, and the inactivation faster and more complex. At +60 mV the channel inactivated with two distinct rates (t1 = 20 ms, t2 = 400 ms). Experiments with tetraethylammonium and high K + concentrations suggest that the slower component was of the P/C-type. In addition, an inactivation component with inverted voltage dependence was introduced. A step to -40 mV inactivates the channel with a time constant of 500 ms. Negative voltage steps do not cause the channel to recover from this inactivated state (t » 10 min), whereas positive voltage steps quickly do (t = 2 ms at +60 mV). The experimental findings can be explained by a simple branched kinetic model with two inactivation pathways from the open state. © 2008 by the Biophysical Society.
Place, publisher, year, edition, pages
2008. Vol. 94, no 8, 3014-3022 p.
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:liu:diva-46421DOI: 10.1529/biophysj.107.119842OAI: oai:DiVA.org:liu-46421DiVA: diva2:267317