Ion Channel Activity of a Synthetic Peptide with a Primary Structure Corresponding to the Presumed Pore-Forming Region of the Voltage Dependent Potassium Channel

Potassium channels are a diverse class of transmembrane proteins that are responsible for diffusion of potassium ion across cell membranes. The lack of large quantities of these proteins from natural sources, is a major hindrance in their structural characterization using biophysical techniques. Synthetic peptide fragments corresponding to functionally important domains of these proteins provide an attractive approach towards characterizing the structural organization of these ion-channels. Conformational properties of peptides from three different potassium channels (Shaker, ROMK1 and minK) have been characterized in aqueous media, organic solvents and in phospholipid membranes. Techniques used for these studies include FTIR, CD and 2D-NMR spectroscopy. FTIR spectroscopy has been a particularly valuable tool for characterizing the folding of the ion-channel peptides in phospholipid membranes; the three different types of potassium channels all share a common transmembrane folding pattern that is composed of a predominantly α-helical structure. There is no evidence to suggest the presence of any significant β-sheet structure. These results are in excellent agreement with the crystal structure of a bacterial potassium channel (Doyle, D. A. et al. (1998) Science280:69–77), and suggest that all potassium channel proteins may share a common folding motif where the ion-channel structure is constructed entirely from α-helices.

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Differential distribution of potassium channels in acutely demyelinated, primary-auditory neurons in vitro

Journal of Neurophysiology ◽

10.1152/jn.1996.76.1.438 ◽

1996 ◽

Vol 76 (1) ◽

pp. 438-447 ◽

Cited By ~ 14

Author(s):

R. L. Davis

Keyword(s):

Potassium Channels ◽

Potassium Channel ◽

Myelin Sheath ◽

Lucifer Yellow ◽

The Other ◽

K Channel ◽

Channel Activity ◽

Auditory Neurons ◽

Axonal Membrane ◽

Voltage Dependent

1. Single-channel recordings of potassium channel activity were made from two populations of primary-auditory neurons maintained in tissue culture. The saccular nerve, which is the auditory component of the eighth cranial nerve in goldfish, was separated into two branches according to its peripheral innervation pattern. Neurons which innervated the rostral saccular macula corresponded to a class of cells that showed spike frequency adaptation; whereas, neurons which innervated the caudal macula were consistent with another type of cell that demonstrated bursting spontaneous firing patterns in vivo. Both somatic and internodal axonal membranes from each of these neuronal classes were studied after acute removal of the myelin sheath by microdissection. 2. Dye injections were used to discriminate neuronal from myelin membrane. After successful removal of the myelin, patch electrodes containing Lucifer yellow were used to fill a neuron and reveal its morphology within the myelin sheath. Patches on myelin led to filling of Schwann cells that surrounded the neuron. 3. Four kinds of potassium channels were observed and characterized according to unitary conductance, inactivation, and sensitivity to internal calcium. Three voltage-dependent K+ channel types were found on the somatic and axonal membrane of the two neuronal populations. Two channel types showed voltage-dependent inactivation and had average conductances of 32 and 19 pS, each with distinctive subconductance states. The third type of channel activity had an estimated conductance of 12 pS and was noninactivating. 4. The fourth type of channel was the Ca2(+)-activated K+ channel (k(Ca)), which was classified by the dependence of its activity on the calcium concentration at its cytoplasmic surface. Unlike the other three potassium channel types, this kind of channel was found exclusively on neurons that innervated the caudal sensory epithelium. As with the other kinds of potassium channels, it was found on both somatic and axonal internodal membranes.

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Solution structure of micelle-bound H5 peptide (427–452): a primary structure corresponding to the pore forming region of the voltage dependent potassium channel

Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology ◽

10.1016/s0167-4838(00)00273-9 ◽

2001 ◽

Vol 1545 (1-2) ◽

pp. 153-159 ◽

Cited By ~ 4

Author(s):

Kazuyasu Shindo ◽

Hideo Takahashi ◽

Kohki Shinozaki ◽

Keiichiro Kami ◽

Kazunori Anzai ◽

...

Keyword(s):

Potassium Channel ◽

Primary Structure ◽

Solution Structure ◽

Voltage Dependent

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A Protein With a Single Transmembrane Domain Forms an Ion Channel

Physiology ◽

10.1152/physiologyonline.1993.8.4.175 ◽

1993 ◽

Vol 8 (4) ◽

pp. 175-178 ◽

Cited By ~ 1

Author(s):

T Takumi

Keyword(s):

Membrane Protein ◽

Ion Channel ◽

Transmembrane Domain ◽

K Channel ◽

Channel Activity ◽

Single Membrane ◽

Voltage Dependent ◽

Membrane Spanning

Isk is a small membrane protein with a single membrane-spanning domain and shows a slow voltage-dependent K+ channel activity. Mutational analyses showed that Isk forms an integral part of the K+ channel itself. Two other proteins have similar properties, suggesting a new group of voltage-dependent channels.

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Structure-based identification and characterisation of novel inhibitors of KNa1.1 potassium channels, a stratified target for KCNT1-related epilepsy

10.1101/779975 ◽

2019 ◽

Author(s):

Bethan A. Cole ◽

Rachel M. Johnson ◽

Hattapark Dejakaisaya ◽

Nadia Pilati ◽

Colin W.G. Fishwick ◽

...

Keyword(s):

Electron Microscopy ◽

Drug Discovery ◽

Ion Channel ◽

Potassium Channel ◽

Mutational Analysis ◽

Drug Resistant ◽

Channel Activity ◽

Epileptic Encephalopathies ◽

Cytotoxicity Assays ◽

Cryo Electron Microscopy

AbstractSeveral types of drug-resistant epileptic encephalopathies of infancy have been associated with mutations in the KCNT1 gene, which encodes the sodium-activated potassium channel subunit KNa1.1. These mutations are commonly gain-of-function, increasing channel activity, therefore inhibition by drugs is proposed as a stratified approach to treat disorders. To date, quinidine therapy has been trialled with several patients, but mostly with unsuccessful outcomes, which has been linked to its low potency and lack of specificity. Here we describe the use of a cryo-electron microscopy-derived KNa1.1 structure and mutational analysis to identify the quinidine biding site and identified novel inhibitors that target this site using computational methods. We describe six compounds that inhibit KNa1.1 channels with low- and sub-micromolar potencies, likely through binding in the intracellular pore vestibule. In preliminary hERG inhibition and cytotoxicity assays, two compounds showed little effect. These compounds may provide starting points for the development of novel pharmacophores for KNa1.1 inhibition, with the view to treating KCNT1-associated epilepsy and, with their potencies higher than quinidine, could become key tool compounds to further study this channel. Furthermore, this study illustrates the potential for utilising cryo-electron microscopy in ion channel drug discovery.

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How Does an Ion Channel Sense Voltage?

Physiology ◽

10.1152/physiologyonline.1997.12.5.203 ◽

1997 ◽

Vol 12 (5) ◽

pp. 203-210 ◽

Cited By ~ 1

Author(s):

DM Papazian ◽

F Bezanilla

Keyword(s):

Ion Channels ◽

Electric Field ◽

Ion Channel ◽

Voltage Sensor ◽

Significant Fraction ◽

Channel Activity ◽

Transmembrane Segments ◽

Voltage Dependent ◽

Ion Conducting ◽

Muscle Excitability

Voltage-dependent ion channels underlie nerve and muscle excitability. Recent studies have increased our understanding of how voltage controls channel activity. Charged residues in transmembrane segments that contribute to the voltage sensor have been identified. During activation, voltage-sensing residues traverse a significant fraction of the transmembrane electric field, dramatically increasing the probability that the channel will enter an open, ion-conducting state.

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