Key result
Zinc bridging reveals S4 and S5 outer ends remain close during Shaker potassium channel opening.
The study provides structural constraints on the movement of the S4 voltage-sensing helix in Kv channels, showing it translates significantly normal to the membrane plane during opening.
Should not yet change arrhythmia management; extends structural models of S4 movement in Kv channels.
The four voltage sensors in voltage-gated potassium (Kv) channels activate upon membrane depolarization and open the pore. The location and motion of the voltage-sensing S4 helix during the early activation steps and the final opening transition are unresolved. We studied Zn(2+) bridges between two introduced His residues in Shaker Kv channels: one in the R1 position at the outer end of the S4 helix (R362H), and another in the S5 helix of the pore domain (A419H or F416H). Zn(2+) bridges readily form between R362H and A419H in open channels after the S4 helix has undergone its final motion. In contrast, a distinct bridge forms between R362H and F416H after early S4 activation, but before the final S4 motion. Both bridges form rapidly, providing constraints on the average position of S4 relative to the pore. These results demonstrate that the outer ends of S4 and S5 remain in close proximity during the final opening transition, with the S4 helix translating a significant distance normal to the membrane plane.
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Phillips et al. (2010) studied Shaker potassium channel function. Introduction of His residues (R362H, A419H, F416H) for Zn(2+) bridge formation was evaluated on Position and motion of the S4 helix relative to the pore. Zn(2+) bridge formation between introduced His residues demonstrated that the outer ends of S4 and S5 remain in close proximity during the final opening transition of Shaker potassium channels.
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