Prof. György PANYI
Institute of Biophysics and Cell Biology, University of Debrecen, Hungary
Contact Prof. György PANYI
Program
"Communication between gates of Shaker K+ channels during slow inactivation"
Voltage-gated K+ channels have distinct gates that regulate ion flux: the activation gate (A-gate) formed by the bundle crossing of the S6 transmembrane helices and the slow inactivation gate in the selectivity filter. Despite major advances in the structure determination of ion channels, the sequence of molecular rearrangements at negative membrane potentials in voltage-gated potassium channels of the Shaker family and the mechanism by which the A-gate and the slow inactivation gate are coupled remained unknown.
To address these we used state-dependent cysteine accessibility studies to evaluate the status of the activation and inactivation gates during steady-state inactivation and upon locking the channel open with intracellular Cd2+. We conclude that at negative membrane potentials, the gating scheme of Shaker channels can be refined in two aspects. First, the most likely pathway for the development of steady-state inactivation is C→O→OI⇌CI. Second, the OI→CI transition is a prerequisite for recovery from inactivation.
The A-gate and the slow inactivation gate are bidirectionally coupled. If coupling involves the rearrangement of the S6 transmembrane segment, then we predict state- dependent changes in the accessibility of S6 residues from the water-filled cavity of the channel with gating. To test this, we engineered cysteines, one at a time, at critical S6 positions in an appropriate Shaker-IR background channel and determined the accessibility of these cysteines to cysteine-modifying reagents MTSET and MTSEA applied to the cytosolic surface of inside- out patches. Our results strongly suggest that the coupling between the A-gate and the slow inactivation gate is mediated by rearrangements in the S6 segment. The S6 rearrangements are consistent with a rigid rod-like rotation of S6 around its longitudinal axis upon inactivation.
Host: Christian GRUBER
Contact for questions: Helmut KUBISTA