Structural basis of two-stage voltage-dependent activation in K<sup>+</sup>channels

Silverman, William R.; Roux, Benoı̂t; Papazian, Diane M.

doi:10.1073/pnas.0636603100

Cited by 89 publications

(133 citation statements)

References 31 publications

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“…6, which is published as supporting information on the PNAS web site). These salt bridges, which stabilize the open-state structure, represent interactions between amino acid residues that are highly conserved among eukaryotic Kv channels (46)(47)(48). Domain Assembly of Kv1.2 in the Open State.…”

Section: Resultsmentioning

confidence: 99%

“…3E), so that the intracellular end of S3 moves closer to the S4-S5 linker. Rotation of S4 around its axis and simultaneous rolling of S2 around S4 allow sequential interactions of the four gating-charge-carrying residues in S4 (R294, R297, R300, and R303 in K v 1.2) with the conserved negatively charged residue in S2 (E226 in K v 1.2) as proposed previously (46)(47)(48). Importantly, S4 rotates relative to S3 during the conformational change in contrast to the movement of these two helices as a rigid helical hairpin as predicted in the paddle model of gating (30).…”

Section: Gatingmentioning

confidence: 98%

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Voltage sensor conformations in the open and closed states in rosetta structural models of K ⁺ channels

Yarov‐Yarovoy¹,

Baker

Catterall³

2006

Proc. Natl. Acad. Sci. U.S.A.

215

249

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Voltage-gated ion channels control generation and propagation of action potentials in excitable cells. Significant progress has been made in understanding structure and function of the voltage-gated ion channels, highlighted by the high-resolution open-state structure of the voltage-gated potassium channel, Kv1.2. However, because the structure of the closed state is unknown, the gating mechanism remains controversial. We adapted the ROSETTA membrane method to model the structures of the Kv1.2 and KvAP channels using homology, de novo, and domain assembly methods and selected the most plausible models using a limited number of experimental constraints. suggests gating movement that can be viewed as a sum of two previously suggested mechanisms: translation (2-4 Å) plus rotation (Ϸ180°) of the S4 segment as proposed in the original ''sliding helix'' or ''helical screw'' models coupled with a rolling motion of the S1-S3 segments around S4, similar to recent ''transporter'' models of gating. We propose a unified mechanism of voltagedependent gating for K v1.2 and KvAP in which this major conformational change moves the gating charge across the electric field in an analogous way for both channels.membrane protein ͉ ROSETTA method ͉ voltage-gated ion channel V oltage-gated potassium (Kv) channels are members of the voltage-gated ion channel superfamily (1, 2), which is important for initiation and propagation of action potentials in excitable cells. They are composed of four identical or homologous subunits, each containing six transmembrane segments: S1-S6. Segments S1-S4 form the voltage-sensing domain (VSD), and segments S5 and S6 connected by the P loop, which is involved in ion selectivity, comprise the pore-forming domain (PD). S4 has four gating-charge-carrying arginines (R1-R4) spaced at intervals of three amino acid residues, which are highly conserved and are thought to play a key role in coupling changes in membrane voltage to opening and closing of the pore (3-5). In the Kv channels Ϸ13 electronic charges cross the membrane electrical field per channel between the closed and open states (6-8).High-resolution structures of the bacterial potassium channel KvAP and the mammalian potassium channel K v 1.2 recently have been solved (9-11). Although the KvAP structures showed the VSD in a nonnative orientation with respect to the membrane and the PD, the K v 1.2 structure captured the VSD in a conformation that is thought to represent the open state of the channel. In addition, the structure reveals that the VSD from one subunit interacts closely with the PD of the adjacent subunit in a clockwise direction when the channel structure is viewed from the extracellular side of the membrane (9). However, the closedstate structure of these channels remains unknown, and the mechanism of action of the voltage sensor in translocating gating charge is a subject of controversy. The original ''sliding helix'' or ''helical screw'' models of gating posited that S4 moves outward along a clockwise spiral path through the protei...

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Section: Resultsmentioning

confidence: 99%

Section: Gatingmentioning

confidence: 98%

Voltage sensor conformations in the open and closed states in rosetta structural models of K ⁺ channels

Yarov‐Yarovoy¹,

Baker

Catterall³

2006

Proc. Natl. Acad. Sci. U.S.A.

215

249

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“…The electrostatic interaction between charged residues helps fold the channel in a proper conformation that efficiently targets the channels to the plasma membrane (31,32). Papazian and colleagues (33,34) also found that divalent ions such as nickel and magnesium can bind to the extracellular ion binding pocket formed by the negatively charged residues at S2 and S3 in ether-à-go-go K ϩ channels, decelerating activation kinetics and/or inhibition of currents. Based on these previous findings, we tested whether the negatively charged residue(s) at the outer portion of IS2 were involved in zinc sensitivity.…”

mentioning

confidence: 99%

Structural Determinants of the High Affinity Extracellular Zinc Binding Site on Cav3.2 T-type Calcium Channels

Kang

Vitko

Lee

et al. 2010

Journal of Biological Chemistry

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Ca v 3.2 T-type channels contain a high affinity metal binding site for trace metals such as copper and zinc. This site is occupied at physiologically relevant concentrations of these metals, leading to decreased channel activity and pain transmission. A histidine at position 191 was recently identified as a critical determinant for both trace metal block of Ca v 3.2 and modulation by redox agents. His 191 is found on the extracellular face of the Ca v 3.2 channel on the IS3-S4 linker and is not conserved in other Ca v 3 channels. Mutation of the corresponding residue in Ca v 3.1 to histidine, Gln 172 , significantly enhances trace metal inhibition, but not to the level observed in wild-type Ca v 3.2, implying that other residues also contribute to the metal binding site. The goal of the present study is to identify these other residues using a series of chimeric channels. The key findings of the study are that the metal binding site is composed of a Asp-Gly-His motif in IS3-S4 and a second aspartate residue in IS2. These results suggest that metal binding stabilizes the closed conformation of the voltage-sensor paddle in repeat I, and thereby inhibits channel opening. These studies provide insight into the structure of T-type channels, and identify an extracellular motif that could be targeted for drug development.

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“…We have shown that bound ions interact with eag-specific acidic residues in transmembrane segments S2 and S3 (Fig. 1A) and have presented evidence that ion binding directly modulates S4 conformational changes (17,19). Interestingly, ion binding slows the kinetics of both ionic and gating currents, but the magnitude of the effect on ionic currents is much greater than on gating currents (16).…”

mentioning

confidence: 99%

Optical detection of rate-determining ion-modulated conformational changes of the ether-à-go-go K ⁺ channel voltage sensor

Bannister

Chanda

Bezanilla

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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In voltage-dependent ether-à -go-go (eag) K ؉ channels, the process of activation is modulated by Mg 2؉ and other divalent cations, which bind to a site in the voltage sensor and slow channel opening. Previous analysis of eag ionic and gating currents indicated that Mg 2؉ has a much larger effect on ionic than gating current kinetics. From this, we hypothesized that ion binding modulates voltage sensor conformational changes that are poorly represented in gating current recordings. We have now tested this proposal by using a combined electrophysiological and optical approach. We find that a fluorescent probe attached near S4 in the voltage sensor reports on two phases of the activation process. One component of the optical signal corresponds to the main charge-moving conformational changes of the voltage sensor. This is the phase of activation that is well represented in gating current recordings. Another component of the optical signal reflects voltage sensor conformational changes that occur at more hyperpolarized potentials. These transitions, which are rate-determining for activation and highly modulated by Mg 2؉ , have not been detected in gating current recordings. Our results demonstrate that the eag voltage sensor undergoes conformational changes that have gone undetected in electrical measurements. These transitions account for the time course of eag activation in the presence and absence of extracellular Mg 2؉ .activation ͉ voltage-gated D rosophila ether-à-go-go (eag) is the original member of a subfamily of voltage-dependent K ϩ channels that includes eag, eag-related gene (erg), and eag-like (elk) channels (1, 2). In mammals, these channels are expressed in the brain and heart, where they play key roles in controlling excitability (2-4). For example, human erg (HERG) channels contribute significantly to the repolarization of the cardiac action potential (3). Disruption of HERG activity results in long QT syndrome, a predisposition to cardiac arrhythmia and sudden death (3,5,6).Eag channels comprise four subunits surrounding a central pore for K ϩ permeation (7). Each subunit has six transmembrane segments. The last two transmembrane segments (S5 and S6) and the intervening P loop form the ion selective pore, whereas S1-S4 form the voltage sensor (8, 9). Voltage control of channel activity is primarily due to the S4 segment, which contains multiple positively charged residues (10). In response to changes in transmembrane voltage, charged residues in S4 initiate conformational changes that control whether the pore is open or closed (11, 12). S4 conformational changes can be measured electrically as gating currents (13).Channels in the eag subfamily are subject to a novel form of regulation by extracellular divalent cations (14-16). In eag channels, the process of voltage-dependent activation is modulated directly by binding of divalent cations to a site in the voltage sensor (16,17). Extracellular divalent ions, including Mg 2ϩ , Mn 2ϩ , and Ni 2ϩ , slow activation kinetics (14, 18). The halfmaximal e...

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Structural basis of two-stage voltage-dependent activation in K⁺channels

Cited by 89 publications

References 31 publications

Voltage sensor conformations in the open and closed states in rosetta structural models of K ⁺ channels

Voltage sensor conformations in the open and closed states in rosetta structural models of K ⁺ channels

Structural Determinants of the High Affinity Extracellular Zinc Binding Site on Cav3.2 T-type Calcium Channels

Optical detection of rate-determining ion-modulated conformational changes of the ether-à-go-go K ⁺ channel voltage sensor

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Structural basis of two-stage voltage-dependent activation in K+channels

Cited by 89 publications

References 31 publications

Voltage sensor conformations in the open and closed states in rosetta structural models of K + channels

Voltage sensor conformations in the open and closed states in rosetta structural models of K + channels

Structural Determinants of the High Affinity Extracellular Zinc Binding Site on Cav3.2 T-type Calcium Channels

Optical detection of rate-determining ion-modulated conformational changes of the ether-à-go-go K + channel voltage sensor

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Resources

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Structural basis of two-stage voltage-dependent activation in K⁺channels

Voltage sensor conformations in the open and closed states in rosetta structural models of K ⁺ channels

Voltage sensor conformations in the open and closed states in rosetta structural models of K ⁺ channels

Optical detection of rate-determining ion-modulated conformational changes of the ether-à-go-go K ⁺ channel voltage sensor