Structural Rearrangements Underlying K
            <sup>+</sup>
            -Channel Activation Gating

Perozo, Eduardo; Marien, D.; Cortés, Jorge; Cuello, Luis G.

doi:10.1126/science.285.5424.73

Cited by 539 publications

(535 citation statements)

References 27 publications

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“…quency 2.50 cm Ϫ1 . This mode revealed a totally concerted tilting and rotation of the transmembrane helices TM1 and TM2 (7)(8)(9)29). The motion of the TM1 helices is mainly a tilting and rotation around a hinge formed between Ser-44 on TM1 and Ser-69 on the small-pore helix.…”

Section: Resultsmentioning

confidence: 99%

“…This cavity is connected to the cytoplasm by a relatively long hydrophobic pore, which is also the location of the intracellular gate of KcsA. Electron paramagnetic resonance (EPR) measurements showed that the diameter of this hydrophobic pore increases when the pH is lowered (7)(8)(9). Minimal change in intersubunit distance near residues Thr-107 to Ala-108 also was observed (9), which led to the speculation that this region serves as a pivot point for the overall motions of the helices.…”

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confidence: 99%

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Intrinsic flexibility and gating mechanism of the potassium channel KcsA

Shen

Kong

2002

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

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The gating mechanism of the potassium channel KcsA was studied by normal mode analysis. The results provided an atomic description of the locations of the pivot points and the motional features of key structural elements in the gating process. Two pivot points were found in the motions of the inner TM2 helical bundle that directly modulate the size of the central channel pore. One point is an intrasubunit hinge point that sharply divides the structural flexibility between the more rigid selectivity filter and the more mobile peripheral transmembrane helices. Such a division is vital for KcsA because it permits the large-scale motions of transmembrane helices required for the gating and, in the meantime, maintains the rigidity of the filter region essential for the selectivity. The other pivot point is an intersubunit one at which all four TM2 helices are bundled together. During the gating process, each TM2 helix undergoes a lever-like swinging motion pivoting on the intrasubunit hinge, and the entire TM2 bundle undergoes a concerted rotational motion around the central channel axis constrained around the intersubunit bundle point. This series of motions leads to a dramatic enlargement of the intracellular gate without loosening up the structural integrity.normal mode analysis ͉ structural flexibility ͉ ion channel K csA is an ion channel that is capable of selecting K ϩ over Na ϩ by a factor of 10 4 and permits the near diffusion-limited throughput rate of 10 8 ions per second (1). KcsA is a tetrameric integral membrane channel protein gated by pH (ref. 2; Fig. 1). Each monomer has two transmembrane helices, TM1 and TM2. The overall shape of the inner core of the channel, formed mainly by the four inner helices TM2, resembles an inverted teepee. There is a selectivity filter located near the extracellular side of the structure, which is highly selective for K ϩ ion. Inside the selectivity filter, main-chain carbonyl oxygen atoms from the filter signature sequence TVGYG are arranged in such a way that the filter energetically favors the transmission of K ϩ or similar cations such as Rb ϩ and Cs ϩ , but not the smaller alkali cations like Na ϩ and Li ϩ (3, 4). Behind the TVGYG sequence is a small-pore helix that supports the selectivity filter. Just before the selectivity filter, roughly in the middle of the membrane, there is a cavity with a diameter of 10 Å, which has been suggested to play a role in stabilizing water molecules and cations in the middle of the phospholipid membrane (5, 6). This cavity is connected to the cytoplasm by a relatively long hydrophobic pore, which is also the location of the intracellular gate of KcsA. Electron paramagnetic resonance (EPR) measurements showed that the diameter of this hydrophobic pore increases when the pH is lowered (7-9). Minimal change in intersubunit distance near residues Thr-107 to Ala-108 also was observed (9), which led to the speculation that this region serves as a pivot point for the overall motions of the helices.The wealth of experimental data provides a...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Intrinsic flexibility and gating mechanism of the potassium channel KcsA

Shen

Kong

2002

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

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“…(1) Upon a positive change in membrane potential S4 moves outward and rotates 180° (Keynes and Elinder 1999). (2) S6 rotates 15° and opens the activation gate (Perozo et al 1999). (3) Residue 451 rotates toward 418, and 450 is removed from its position in the aromatic cuff (Larsson and Elinder 2000).…”

Section: Tablementioning

confidence: 99%

S4 Charges Move Close to Residues in the Pore Domain during Activation in a K Channel

Elinder

Männikkö

Larsson

2001

The Journal of General Physiology

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Voltage-gated ion channels respond to changes in the transmembrane voltage by opening or closing their ion conducting pore. The positively charged fourth transmembrane segment (S4) has been identified as the main voltage sensor, but the mechanisms of coupling between the voltage sensor and the gates are still unknown. Obtaining information about the location and the exact motion of S4 is an important step toward an understanding of these coupling mechanisms. In previous studies we have shown that the extracellular end of S4 is located close to segment 5 (S5). The purpose of the present study is to estimate the location of S4 charges in both resting and activated states. We measured the modification rates by differently charged methanethiosulfonate regents of two residues in the extracellular end of S5 in the Shaker K channel (418C and 419C). When S4 moves to its activated state, the modification rate by the negatively charged sodium (2-sulfonatoethyl) methanethiosulfonate (MTSES−) increases significantly more than the modification rate by the positively charged [2-(trimethylammonium)ethyl] methanethiosulfonate, bromide (MTSET+). This indicates that the positive S4 charges are moving close to 418C and 419C in S5 during activation. Neutralization of the most external charge of S4 (R362), shows that R362 in its activated state electrostatically affects the environment at 418C by 19 mV. In contrast, R362 in its resting state has no effect on 418C. This suggests that, during activation of the channel, R362 moves from a position far away (>20 Å) to a position close (8 Å) to 418C. Despite its close approach to E418, a residue shown to be important in slow inactivation, R362 has no effect on slow inactivation or the recovery from slow inactivation. This refutes previous models for slow inactivation with an electrostatic S4-to-gate coupling. Instead, we propose a model with an allosteric mechanism for the S4-to-gate coupling.

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“…The inner KcsA helices form an important part of the conduction pathway. Previous electron paramagnetic resonance experiments showed that they rotate upon activation in a counterclockwise direction, thereby opening the conduction pathway (15,16). Furthermore, solid-state NMR (ssNMR), which can be applied in lipid bilayers (17)(18)(19)(20), provided detailed insights into the structural basis of the coupling of KcsA activation and inactivation gates during channel gating (21)(22)(23).…”

Section: Introductionmentioning

confidence: 99%

Probing Conformational Changes during the Gating Cycle of a Potassium Channel in Lipid Bilayers

Cruijsen

Prokofyev

Pongs

et al. 2017

Biophysical Journal

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Ion conduction across the cellular membrane requires the simultaneous opening of activation and inactivation gates of the K þ channel pore. The bacterial KcsA channel has served as a powerful system for dissecting the structural changes that are related to four major functional states associated with K þ gating. Yet, the direct observation of the full gating cycle of KcsA has remained structurally elusive, and crystal structures mimicking these gating events require mutations in or stabilization of functionally relevant channel segments. Here, we found that changes in lipid composition strongly increased the KcsA open probability. This enabled us to probe all four major gating states in native-like membranes by combining electrophysiological and solid-state NMR experiments. In contrast to previous crystallographic views, we found that the selectivity filter and turret region, coupled to the surrounding bilayer, were actively involved in channel gating. The increase in overall steady-state open probability was accompanied by a reduction in activation-gate opening, underscoring the important role of the surrounding lipid bilayer in the delicate conformational coupling of the inactivation and activation gates.

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Structural Rearrangements Underlying K ⁺ -Channel Activation Gating

Cited by 539 publications

References 27 publications

Intrinsic flexibility and gating mechanism of the potassium channel KcsA

Intrinsic flexibility and gating mechanism of the potassium channel KcsA

S4 Charges Move Close to Residues in the Pore Domain during Activation in a K Channel

Probing Conformational Changes during the Gating Cycle of a Potassium Channel in Lipid Bilayers

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Structural Rearrangements Underlying K + -Channel Activation Gating

Cited by 539 publications

References 27 publications

Intrinsic flexibility and gating mechanism of the potassium channel KcsA

Intrinsic flexibility and gating mechanism of the potassium channel KcsA

S4 Charges Move Close to Residues in the Pore Domain during Activation in a K Channel

Probing Conformational Changes during the Gating Cycle of a Potassium Channel in Lipid Bilayers

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Structural Rearrangements Underlying K ⁺ -Channel Activation Gating