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The activation of Shaker K+ channels is steeply voltage dependent. To determine whether conserved charged amino acids in putative transmembrane segments S2, S3, and S4 contribute to the gating charge of the channel, the total gating charge movement per channel was measured in channels containing neutralization mutations. Of eight residues tested, four(More)
Ionic (Ii) and gating currents (Ig) from noninactivating Shaker H4 K+ channels were recorded with the cut-open oocyte voltage clamp and macropatch techniques. Steady state and kinetic properties were studied in the temperature range 2-22 degreesC. The time course of Ii elicited by large depolarizations consists of an initial delay followed by an exponential(More)
Gating currents provide a direct record of the spatial rearrangement of charges occurring within the protein of voltage-sensitive ion channels. If the elementary charges move as very brief discrete pulses of current, they will produce fluctuations in the macroscopic gating current. The variance of such fluctuations in gating currents was measured in Shaker(More)
One measure of the voltage dependence of ion channel conductance is the amount of gating charge that moves during activation and vice versa. The limiting slope method, introduced by Almers (Almers, W. 1978. Rev. Physiol. Biochem. Pharmacol. 82:96-190), exploits the relationship of charge movement and voltage sensitivity, yielding a lower limit to the range(More)
Excitation-evoked calcium influx across cellular membranes is strictly controlled by voltage-gated calcium channels (CaV), which possess four distinct voltage-sensing domains (VSDs) that direct the opening of a central pore. The energetic interactions between the VSDs and the pore are critical for tuning the channel's voltage dependence. The accessory α2δ-1(More)
A thermodynamic approach to studying allosterically regulated ion channels such as the large-conductance voltage- and Ca(2+)-dependent (BK) channel is presented, drawing from principles originally introduced to describe linkage phenomena in hemoglobin. In this paper, linkage between a principal channel component and secondary elements is derived from a(More)
We have developed a method for rapidly computing gating currents from a multiparticle ion channel model. Our approach is appropriate for energy landscapes that can be characterized by a network of well-defined activation pathways with barriers. To illustrate, we represented the gating apparatus of a channel subunit by an interacting pair of charged gating(More)
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,(More)
The Laser Interferometer Gravitational-Wave Observatory has performed a third science run with much improved sensitivities of all three interferometers. We present an analysis of approximately 200 hours of data acquired during this run, used to search for a stochastic background of gravitational radiation. We place upper bounds on the energy density stored(More)
Excitation-evoked Ca(2+) influx is the fastest and most ubiquitous chemical trigger for cellular processes, including neurotransmitter release, muscle contraction, and gene expression. The voltage dependence and timing of Ca(2+) entry are thought to be functions of voltage-gated calcium (CaV) channels composed of a central pore regulated by four(More)