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Wang F, Chang S, Wei D. Prediction of conotoxin type based on long short-term memory network. MATHEMATICAL BIOSCIENCES AND ENGINEERING : MBE 2021; 18:6700-6708. [PMID: 34517552 DOI: 10.3934/mbe.2021332] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Aiming at the problems of the wet experiment method in identifying the types of conotoxins, such as the complexity, low efficiency and high cost, this study proposes a method that uses the sequence information of the conotoxin peptides combined with long short term memory networks (LSTM) models to predict the Methods of spirotoxin category. This method only needs to take the conotoxin peptide sequence as input, and adopts the character embedding method in text processing to automatically map the sequence to the feature vector representation, and the model extracts features for training and prediction. Experimental results show that the correct index of this method on the test set reaches 0.80, and the AUC value reaches 0.817. For the same test set, the AUC value of the KNN algorithm is 0.641, and the AUC value of the method proposed in this paper is 0.817, indicating that this method can effectively assist in identifying the type of conotoxin.
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Affiliation(s)
- Feng Wang
- Changzhou University Huaide College, China
| | - Shan Chang
- Institute of Bioinformatics and Medical Engineering, School of Electrical and Information Engineering, Jiangsu University of Technology, Changzhou, China
| | - Dashun Wei
- Changzhou University Huaide College, China
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2
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Chatterjee S, Vyas R, Chalamalasetti SV, Sahu ID, Clatot J, Wan X, Lorigan GA, Deschênes I, Chakrapani S. The voltage-gated sodium channel pore exhibits conformational flexibility during slow inactivation. J Gen Physiol 2018; 150:1333-1347. [PMID: 30082431 PMCID: PMC6122925 DOI: 10.1085/jgp.201812118] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 07/06/2018] [Indexed: 01/02/2023] Open
Abstract
Voltage-gated sodium channels undergo slow inactivation during prolonged depolarization by means of a mechanism that is poorly understood. Chatterjee et al. study this process spectroscopically and reveal conformational flexibility of the pore region in the slow-inactivated state. Slow inactivation in voltage-gated sodium channels (NaVs) directly regulates the excitability of neurons, cardiac myocytes, and skeletal muscles. Although NaV slow inactivation appears to be conserved across phylogenies—from bacteria to humans—the structural basis for this mechanism remains unclear. Here, using site-directed labeling and EPR spectroscopic measurements of membrane-reconstituted prokaryotic NaV homologues, we characterize the conformational dynamics of the selectivity filter region in the conductive and slow-inactivated states to determine the molecular events underlying NaV gating. Our findings reveal profound conformational flexibility of the pore in the slow-inactivated state. We find that the P1 and P2 pore helices undergo opposing movements with respect to the pore axis. These movements result in changes in volume of both the central and intersubunit cavities, which form pathways for lipophilic drugs that modulate slow inactivation. Our findings therefore provide novel insight into the molecular basis for state-dependent effects of lipophilic drugs on channel function.
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Affiliation(s)
- Soumili Chatterjee
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH
| | - Rajan Vyas
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH
| | | | - Indra D Sahu
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH
| | - Jérôme Clatot
- Heart and Vascular Research Center, Department of Medicine, Case Western Reserve University, Cleveland, OH
| | - Xiaoping Wan
- Heart and Vascular Research Center, Department of Medicine, Case Western Reserve University, Cleveland, OH
| | - Gary A Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH
| | - Isabelle Deschênes
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH.,Heart and Vascular Research Center, Department of Medicine, Case Western Reserve University, Cleveland, OH
| | - Sudha Chakrapani
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH
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3
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Distinct modulation of inactivation by a residue in the pore domain of voltage-gated Na + channels: mechanistic insights from recent crystal structures. Sci Rep 2018; 8:631. [PMID: 29330525 PMCID: PMC5766632 DOI: 10.1038/s41598-017-18919-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 12/18/2017] [Indexed: 12/19/2022] Open
Abstract
Inactivation of voltage-gated Na+ channels (VGSC) is essential for the regulation of cellular excitability. The molecular rearrangement underlying inactivation is thought to involve the intracellular linker between domains III and IV serving as inactivation lid, the receptor for the lid (domain III S4-S5 linker) and the pore-lining S6 segements. To better understand the role of the domain IV S6 segment in inactivation we performed a cysteine scanning mutagenesis of this region in rNav 1.4 channels and screened the constructs for perturbations in the voltage-dependence of steady state inactivation. This screen was performed in the background of wild-type channels and in channels carrying the mutation K1237E, which profoundly alters both permeation and gating-properties. Of all tested constructs the mutation I1581C was unique in that the mutation-induced gating changes were strongly influenced by the mutational background. This suggests that I1581 is involved in specific short-range interactions during inactivation. In recently published crystal structures VGSCs the respective amino acids homologous to I1581 appear to control a bend of the S6 segment which is critical to the gating process. Furthermore, I1581 may be involved in the transmission of the movement of the DIII voltage-sensor to the domain IV S6 segment.
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4
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Mangold KE, Brumback BD, Angsutararux P, Voelker TL, Zhu W, Kang PW, Moreno JD, Silva JR. Mechanisms and models of cardiac sodium channel inactivation. Channels (Austin) 2017; 11:517-533. [PMID: 28837385 PMCID: PMC5786193 DOI: 10.1080/19336950.2017.1369637] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Revised: 08/14/2017] [Accepted: 08/15/2017] [Indexed: 12/19/2022] Open
Abstract
Shortly after cardiac Na+ channels activate and initiate the action potential, inactivation ensues within milliseconds, attenuating the peak Na+ current, INa, and allowing the cell membrane to repolarize. A very limited number of Na+ channels that do not inactivate carry a persistent INa, or late INa. While late INa is only a small fraction of peak magnitude, it significantly prolongs ventricular action potential duration, which predisposes patients to arrhythmia. Here, we review our current understanding of inactivation mechanisms, their regulation, and how they have been modeled computationally. Based on this body of work, we conclude that inactivation and its connection to late INa would be best modeled with a "feet-on-the-door" approach where multiple channel components participate in determining inactivation and late INa. This model reflects experimental findings showing that perturbation of many channel locations can destabilize inactivation and cause pathological late INa.
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Affiliation(s)
- Kathryn E. Mangold
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Brittany D. Brumback
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Paweorn Angsutararux
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Taylor L. Voelker
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Wandi Zhu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Po Wei Kang
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Jonathan D. Moreno
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Jonathan R. Silva
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
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5
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Linsdell P. Metal bridges to probe membrane ion channel structure and function. Biomol Concepts 2016; 6:191-203. [PMID: 26103632 DOI: 10.1515/bmc-2015-0013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 05/29/2015] [Indexed: 11/15/2022] Open
Abstract
Ion channels are integral membrane proteins that undergo important conformational changes as they open and close to control transmembrane flux of different ions. The molecular underpinnings of these dynamic conformational rearrangements are difficult to ascertain using current structural methods. Several functional approaches have been used to understand two- and three-dimensional dynamic structures of ion channels, based on the reactivity of the cysteine side-chain. Two-dimensional structural rearrangements, such as changes in the accessibility of different parts of the channel protein to the bulk solution on either side of the membrane, are used to define movements within the permeation pathway, such as those that open and close ion channel gates. Three-dimensional rearrangements – in which two different parts of the channel protein change their proximity during conformational changes – are probed by cross-linking or bridging together two cysteine side-chains. Particularly useful in this regard are so-called metal bridges formed when two or more cysteine side-chains form a high-affinity binding site for metal ions such as Cd2+ or Zn2+. This review describes the use of these different techniques for the study of ion channel dynamic structure and function, including a comprehensive review of the different kinds of conformational rearrangements that have been studied in different channel types via the identification of intra-molecular metal bridges. Factors that influence the affinities and conformational sensitivities of these metal bridges, as well as the kinds of structural inferences that can be drawn from these studies, are also discussed.
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Abstract
Prolonged depolarizing pulses that last seconds to minutes cause slow inactivation of Na(+) channels, which regulates neuron and myocyte excitability by reducing availability of inward current. In neurons, slow inactivation has been linked to memory of previous excitation and in skeletal muscle it ensures myocytes are able to contract when K(+) is elevated. The molecular mechanisms underlying slow inactivation are unclear even though it has been studied for 50+ years. This chapter reviews what is known to date regarding the definition, measurement, and mechanisms of voltage-gated Na(+) channel slow inactivation.
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Affiliation(s)
- Jonathan Silva
- Department of Biomedical Engineering, Washington University in St. Louis, Campus Box 1097, St. Louis, MO, 63116, USA,
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7
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Silva JR, Goldstein SAN. Voltage-sensor movements describe slow inactivation of voltage-gated sodium channels I: wild-type skeletal muscle Na(V)1.4. ACTA ACUST UNITED AC 2013; 141:309-21. [PMID: 23401571 PMCID: PMC3581692 DOI: 10.1085/jgp.201210909] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The number of voltage-gated sodium (NaV) channels available to generate action potentials in muscles and nerves is adjusted over seconds to minutes by prior electrical activity, a process called slow inactivation (SI). The basis for SI is uncertain. NaV channels have four domains (DI–DIV), each with a voltage sensor that moves in response to depolarizing stimulation over milliseconds to activate the channels. Here, SI of the skeletal muscle channel NaV1.4 is induced by repetitive stimulation and is studied by recording of sodium currents, gating currents, and changes in the fluorescence of probes on each voltage sensor to assess their movements. The magnitude, voltage dependence, and time course of the onset and recovery of SI are observed to correlate with voltage-sensor movements 10,000-fold slower than those associated with activation. The behavior of each voltage sensor is unique. Development of SI over 1–160 s correlates best with slow immobilization of the sensors in DI and DII; DIII tracks the onset of SI with less fidelity. Showing linkage to the sodium conduction pathway, pore block by tetrodotoxin affects both SI and immobilization of all the sensors, with DI and DII significantly suppressed. Recovery from SI correlates best with slow restoration of mobility of the sensor in DIII. The findings suggest that voltage-sensor movements determine SI and thereby mediate NaV channel availability.
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Affiliation(s)
- Jonathan R Silva
- Department of Biochemistry, Brandeis University, Waltham, MA 02453, USA
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8
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Mechanism of Cd2+ coordination during slow inactivation in potassium channels. Structure 2012; 20:1332-42. [PMID: 22771214 DOI: 10.1016/j.str.2012.03.027] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Revised: 01/14/2012] [Accepted: 03/27/2012] [Indexed: 11/22/2022]
Abstract
In K+ channels, rearrangements of the pore outer vestibule have been associated with C-type inactivation gating. Paradoxically, the crystal structure of Open/C-type inactivated KcsA suggests these movements to be modest in magnitude. In this study, we show that under physiological conditions, the KcsA outer vestibule undergoes relatively large dynamic rearrangements upon inactivation. External Cd2+ enhances the rate of C-type inactivation in an cysteine mutant (Y82C) via metal-bridge formation. This effect is not present in a non-inactivating mutant (E71A/Y82C). Tandem dimer and tandem tetramer constructs of equivalent cysteine mutants in KcsA and Shaker K+ channels demonstrate that these Cd2+ metal bridges are formed only between adjacent subunits. This is well supported by molecular dynamics simulations. Based on the crystal structure of Cd2+ -bound Y82C-KcsA in the closed state, together with electron paramagnetic resonance distance measurements in the KcsA outer vestibule, we suggest that subunits must dynamically come in close proximity as the channels undergo inactivation.
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A residue W756 in the P-loop segment of the sodium channel is critical for primaquine binding. Eur J Pharmacol 2011; 663:1-8. [DOI: 10.1016/j.ejphar.2011.04.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Revised: 03/17/2011] [Accepted: 04/06/2011] [Indexed: 11/18/2022]
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10
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Zarrabi T, Cervenka R, Sandtner W, Lukacs P, Koenig X, Hilber K, Mille M, Lipkind GM, Fozzard HA, Todt H. A molecular switch between the outer and the inner vestibules of the voltage-gated Na+ channel. J Biol Chem 2010; 285:39458-70. [PMID: 20926383 PMCID: PMC2998134 DOI: 10.1074/jbc.m110.132886] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Voltage-gated ion channels are transmembrane proteins that undergo complex conformational changes during their gating transitions. Both functional and structural data from K+ channels suggest that extracellular and intracellular parts of the pore communicate with each other via a trajectory of interacting amino acids. No crystal structures are available for voltage-gated Na+ channels, but functional data suggest a similar intramolecular communication involving the inner and outer vestibules. However, the mechanism of such communication is unknown. Here, we report that amino acid Ile-1575 in the middle of transmembrane segment 6 of domain IV (DIV-S6) in the adult rat skeletal muscle isoform of the voltage-gated sodium channel (rNaV1.4) may act as molecular switch allowing for interaction between outer and inner vestibules. Cysteine scanning mutagenesis of the internal part of DIV-S6 revealed that only mutations at site 1575 rescued the channel from a unique kinetic state (“ultra-slow inactivation,” IUS) produced by the mutation K1237E in the selectivity filter. A similar effect was seen with I1575A. Previously, we reported that conformational changes of both the internal and the external vestibule are involved in the generation of IUS. The fact that mutations at site 1575 modulate IUS produced by K1237E strongly suggests an interaction between these sites. Our data confirm a previously published molecular model in which Ile-1575 of DIV-S6 is in close proximity to Lys-1237 of the selectivity filter. Furthermore, these functional data define the position of the selectivity filter relative to the adjacent DIV-S6 segment within the ionic permeation pathway.
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Affiliation(s)
- Touran Zarrabi
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna 1090, Austria
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11
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Cervenka R, Zarrabi T, Lukacs P, Todt H. The outer vestibule of the Na+ channel-toxin receptor and modulator of permeation as well as gating. Mar Drugs 2010; 8:1373-93. [PMID: 20479982 PMCID: PMC2866490 DOI: 10.3390/md8041373] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Revised: 03/31/2010] [Accepted: 04/19/2010] [Indexed: 12/19/2022] Open
Abstract
The outer vestibule of voltage-gated Na(+) channels is formed by extracellular loops connecting the S5 and S6 segments of all four domains ("P-loops"), which fold back into the membrane. Classically, this structure has been implicated in the control of ion permeation and in toxin blockage. However, conformational changes of the outer vestibule may also result in alterations in gating, as suggested by several P-loop mutations that gave rise to gating changes. Moreover, partial pore block by mutated toxins may reverse gating changes induced by mutations. Therefore, toxins that bind to the outer vestibule can be used to modulate channel gating.
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Affiliation(s)
| | | | - Peter Lukacs
- Institute of Pharmacology, Centre of Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria; E-Mails:
(R.C.);
(T.Z.);
(P.L.)
| | - Hannes Todt
- Institute of Pharmacology, Centre of Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria; E-Mails:
(R.C.);
(T.Z.);
(P.L.)
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12
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Eckle VS, Todorovic SM. Mechanisms of inhibition of CaV3.1 T-type calcium current by aliphatic alcohols. Neuropharmacology 2010; 59:58-69. [PMID: 20363234 DOI: 10.1016/j.neuropharm.2010.03.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2010] [Revised: 03/25/2010] [Accepted: 03/26/2010] [Indexed: 11/30/2022]
Abstract
Many aliphatic alcohols modulate activity of various ion channels involved in sensory processing and also exhibit anesthetic capacity in vivo. Although the interaction of one such compound, 1-octanol (octanol) with different T-type calcium channels (T-channels) has been described, the mechanisms of current modulation and its functional significance are not well studied. Using patch-clamp technique, we investigated the mechanisms of inhibition of T-currents by a series of aliphatic alcohols in recombinant human Ca(V)3.1 (alpha1G) T-channel isoform expressed in human embryonic kidney (HEK) 293 cells and thalamocortical (TC) relay neurons in brain slices of young rats. Octanol, 1-heptanol (heptanol) and 1-hexanol (hexanol) inhibited the recombinant Ca(V)3.1 currents in concentration-dependent manner yielding IC(50) values of 362 microM, 1063 microM and 3167 microM, respectively. Octanol similarly inhibited native thalamic Ca(V)3.1 T-currents with an IC(50) of 287 microM and diminished burst firing without significant effect on passive membrane properties of these neurons. Inhibitory effect of octanol on T-currents in both native and recombinant cells was accompanied with accelerated macroscopic inactivation kinetics and hyperpolarizing shift in the steady-state inactivation curve. Additionally, octanol induced a depolarizing shift in steady-state activation curves of T-current in TC neurons. Surprisingly, the recovery from fast inactivation at hyperpolarized membrane potentials was accelerated by octanol up 3-fold in native but not recombinant channels. Given the importance of thalamocortical pathways in providing sleep, arousal, and anesthetic states, modulation of thalamic T-currents may at least contribute to the pharmacological effects of aliphatic alcohols.
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Affiliation(s)
- Veit-Simon Eckle
- Department of Anesthesiology, University of Virginia Health System, School of Medicine, Charlottesville, VA 22908-0710, USA
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13
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Yamagishi T, Xiong W, Kondratiev A, Vélez P, Méndez-Fitzwilliam A, Balser JR, Marbán E, Tomaselli GF. Novel molecular determinants in the pore region of sodium channels regulate local anesthetic binding. Mol Pharmacol 2009; 76:861-71. [PMID: 19620257 DOI: 10.1124/mol.109.055863] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
The pore of the Na+ channel is lined by asymmetric loops formed by the linkers between the fifth and sixth transmembrane segments (S5-S6). We investigated the role of the N-terminal portion (SS1) of the S5-S6 linkers in channel gating and local anesthetic (LA) block using site-directed cysteine mutagenesis of the rat skeletal muscle (Na(V)1.4) channel. The mutants examined have variable effects on voltage dependence and kinetics of fast inactivation. Of the cysteine mutants immediately N-terminal to the putative DEKA selectivity filter in four domains, only Q399C in domain I and F1236C in domain III exhibit reduced use-dependent block. These two mutations also markedly accelerated the recovery from use-dependent block. Moreover, F1236C and Q399C significantly decreased the affinity of QX-314 for binding to its channel receptor by 8.5- and 3.3-fold, respectively. Oddly enough, F1236C enhanced stabilization of slow inactivation by both hastening entry into and delaying recovery from slow inactivation states. It is noteworthy that symmetric applications of QX-314 on both external and internal sides of F1236C mutant channels reduced recovery from use-dependent block, indicating an allosteric effect of external QX-314 binding on the recovery of availability of F1236C. These observations suggest that cysteine mutation in the SS1 region, particularly immediate adjacent to the DEKA ring, may lead to a structural rearrangement that alters binding of permanently charged QX-314 to its receptor. The results lend further support for a role for the selectivity filter region as a structural determinant for local anesthetic block.
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Affiliation(s)
- Toshio Yamagishi
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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Wang S, Alimi Y, Tong A, Nichols CG, Enkvetchakul D. Differential roles of blocking ions in KirBac1.1 tetramer stability. J Biol Chem 2008; 284:2854-2860. [PMID: 19033439 DOI: 10.1074/jbc.m807474200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Potassium channels are tetrameric proteins that mediate K(+)-selective transmembrane diffusion. For KcsA, tetramer stability depends on interactions between permeant ions and the channel pore. We have examined the role of pore blockers on the tetramer stability of KirBac1.1. In 150 mm KCl, purified KirBac1.1 protein migrates as a monomer (approximately 40 kDa) on SDS-PAGE. Addition of Ba(2+) (K(1/2) approximately 50 microm) prior to loading results in an additional tetramer band (approximately 160 kDa). Mutation A109C, at a residue located near the expected Ba(2+)-binding site, decreased tetramer stabilization by Ba(2+) (K(1/2) approximately 300 microm), whereas I131C, located nearby, stabilized tetramers in the absence of Ba(2+). Neither mutation affected Ba(2+) block of channel activity (using (86)Rb(+) flux assay). In contrast to Ba(2+), Mg(2+) had no effect on tetramer stability (even though Mg(2+) was a potent blocker). Many studies have shown Cd(2+) block of K(+) channels as a result of cysteine substitution of cavity-lining M2 (S6) residues, with the implicit interpretation that coordination of a single ion by cysteine side chains along the central axis effectively blocks the pore. We examined blocking and tetramer-stabilizing effects of Cd(2+) on KirBac1.1 with cysteine substitutions in M2. Cd(2+) block potency followed an alpha-helical pattern consistent with the crystal structure. Significantly, Cd(2+) strongly stabilized tetramers of I138C, located in the center of the inner cavity. This stabilization was additive with the effect of Ba(2+), consistent with both ions simultaneously occupying the channel: Ba(2+) at the selectivity filter entrance and Cd(2+) coordinated by I138C side chains in the inner cavity.
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Affiliation(s)
- Shizhen Wang
- Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, St. Louis, Missouri 63104; Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Yewande Alimi
- Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, St. Louis, Missouri 63104
| | - Ailing Tong
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Colin G Nichols
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Decha Enkvetchakul
- Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, St. Louis, Missouri 63104.
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