Key result
High-speed patch-clamp reveals an early ~12 microsecond Shaker K+ gating current modeled as Brownian motion.
Why the study?
The early component of gating current in Shaker K+ channels and its energy landscape during activation were not fully characterized.
The study provides a biophysical model of Shaker K+ channel activation, suggesting the channel experiences incremental organization from a relaxed state to a rigidly structured open state.
Advances K+ channel gating models; leaves open translation to cardiac excitability or channelopathies.
An early component of the gating current in Shaker K+ channels with a time constant of approximately 12 microsec has been recorded with a high-speed patch-clamp setup. This fast component was found to be part of the gating current associated with the opening and closing of the channel. With regard to an energy-landscape interpretation of protein kinetics, the voltage and temperature dependence of the fast component may be explained by a combination of drift diffusion and barrier jumping in the initial stages of channel activation. The data were modeled by a gating particle undergoing Brownian motion in a one-dimensional diffusion landscape that featured diminishing electrical resistance and entropy in the direction of channel activation. The final open state of the channel was reasoned to be narrow and deep to account for successful subtraction of linear-charge displacements at positive potentials. The overall picture of gating that emerges from these studies is that the channel experiences incremental organization from a relaxed state in the early steps of activation to a rigidly structured open state.
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Sigg et al. (2003) studied this question. High-speed patch-clamp recording was evaluated on Fast component of the gating current. An early component of the gating current in Shaker K+ channels with a time constant of approximately 12 microsec was identified and modeled as a gating particle undergoing Brownian motion.
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