scholarly journals Mapping the Binding Site of a Humanether-a-go-go-related Gene-specific Peptide Toxin (ErgTx) to the Channel's Outer Vestibule

2002 ◽  
Vol 277 (19) ◽  
pp. 16403-16411 ◽  
Author(s):  
Liliana Pardo-Lopez ◽  
Mei Zhang ◽  
Jie Liu ◽  
Min Jiang ◽  
Lourival D. Possani ◽  
...  
Keyword(s):  
Binding Site ◽  
Related Gene ◽  
Outer Vestibule ◽  
Peptide Toxin ◽  
Specific Peptide

The promoter of the HaCaT keratinocyte differentiation-related gene keratin 4 contains a functional AP-2 binding site

1997 ◽  
Vol 289 (12) ◽  
pp. 705-708 ◽  
Author(s):  
R. Wanner ◽  
Juan Zhang ◽  
Tomislav Dorbic ◽  
Dietmar Mischke ◽  
Beate M. Henz ◽  
...  
Keyword(s):  
Binding Site ◽  
Keratinocyte Differentiation ◽  
Related Gene ◽  
Hacat Keratinocyte

scholarly journals A mu-conotoxin-insensitive Na+ channel mutant: possible localization of a binding site at the outer vestibule

1995 ◽  
Vol 69 (5) ◽  
pp. 1657-1665 ◽  
Author(s):  
S.C. Dudley ◽  
H. Todt ◽  
G. Lipkind ◽  
H.A. Fozzard
Keyword(s):  
Binding Site ◽  
Na Channel ◽  
Outer Vestibule

scholarly journals Three-Dimensional Location of the Imperatoxin a Binding Site on the Ryanodine Receptor

1999 ◽  
Vol 146 (2) ◽  
pp. 493-500 ◽  
Author(s):  
Montserrat Samsó ◽  
Ramon Trujillo ◽  
Georgina B. Gurrola ◽  
Hector H. Valdivia ◽  
Terence Wagenknecht
Keyword(s):  
Binding Site ◽  
Ryanodine Receptor ◽  
Calcium Release ◽  
Particle Image ◽  
Specific Binding ◽  
Three Dimensional ◽  
Calcium Release Channel ◽  
Release Channel ◽  
Cryo Electron Microscopy ◽  
Peptide Toxin

Cryo-electron microscopy and three-dimensional, single-particle image analysis have been used to reveal the specific binding site of imperatoxin A (IpTxa) on the architecture of the calcium release channel/ryanodine receptor from skeletal muscle (RyR1). IpTxa is a peptide toxin that binds with high affinity to RyR1 and affects its functioning. The toxin was derivatized with biotin to enhance its detection with streptavidin. IpTxa binds to the cytoplasmic moiety of RyR1 between the clamp and handle domains, 11 nm away from the transmembrane pore. The proposed mimicry by IpTxa of the dihydropyridine receptor (DHPR) II-III loop, thought to be a main physiological excitation-contraction trigger, suggests that the IpTxa binding location is a potential excitation-contraction signal transduction site.

scholarly journals Pseudechetoxin Binds to the Pore Turret of Cyclic Nucleotide–gated Ion Channels

2003 ◽  
Vol 122 (6) ◽  
pp. 749-760 ◽  
Author(s):  
R. Lane Brown ◽  
Leatha L. Lynch ◽  
Tammie L. Haley ◽  
Reza Arsanjani
Keyword(s):  
Ion Channels ◽  
Binding Site ◽  
Cyclic Nucleotide ◽  
Critical Role ◽  
Sensory Transduction ◽  
Amino Acid Residues ◽  
High Affinity ◽  
Primary Determinant ◽  
Olfactory Systems ◽  
Peptide Toxin

Peptide toxins are invaluable tools for studying the structure and physiology of ion channels. Pseudechetoxin (PsTx) is the first known peptide toxin that targets cyclic nucleotide–gated (CNG) ion channels, which play a critical role in sensory transduction in the visual and olfactory systems. PsTx inhibited channel currents at low nM concentrations when applied to the extracellular face of membrane patches expressing olfactory CNGA2 subunits. Surprisingly, 500 nM PsTx did not inhibit currents through channels formed by the CNGA3 subunit from cone photoreceptors. We have exploited this difference to identify the PsTx-binding site on the extracellular face of CNG channels. Studies using chimeric channels revealed that transplantation of the pore domain from CNGA2 was sufficient to confer high affinity PsTx binding upon a CNGA3 background. To further define the binding site, reciprocal mutations were made at 10 nonidentical amino acid residues in this region. We found that two residues in CNGA2, D316 and Y321, were essential for high-affinity inhibition by PsTx. Furthermore, replacement of both residues was required to confer high-affinity PsTx inhibition upon CNGA3. Several other residues, including E325, also form favorable interactions with PsTx. In the CNGA2-E325K mutant, PsTx affinity was reduced by ∼5-fold to 120 nM. An electrostatic interaction with D316 does not appear to be the primary determinant of PsTx affinity, as modification of the D316C mutant with a negatively charged methanethiosulfonate reagent did not restore high affinity inhibition. The residues involved in PsTx binding are found within the pore turret and helix, in similar positions to residues that form the receptor for pore-blocking toxins in voltage-gated potassium channels. Furthermore, biophysical properties of PsTx block, including an unfavorable interaction with permeant ions, also suggest that it acts as a pore blocker. In summary, PsTx seems to occlude the entrance to the pore by forming high-affinity contacts with the pore turret, which may be larger than that found in the KcsA structure.

scholarly journals Inhibition of the Collapse of the Shaker K+ Conductance by Specific Scorpion Toxins

2004 ◽  
Vol 123 (3) ◽  
pp. 265-279 ◽  
Author(s):  
Froylan Gómez-Lagunas ◽  
Cesar V.F. Batista ◽  
Timoteo Olamendi-Portugal ◽  
Martha E. Ramírez-Domínguez ◽  
Lourival D. Possani
Keyword(s):  
Binding Site ◽  
Selectivity Filter ◽  
Channel Block ◽  
Scorpion Toxins ◽  
K Channels ◽  
Outer Vestibule ◽  
Plausible Model ◽  
K Current ◽  
Do So ◽  
External K

The Shaker B K+ conductance (GK) collapses when the channels are closed (deactivated) in Na+ solutions that lack K+ ions. Also, it is known that external TEA (TEAo) impedes the collapse of GK (Gómez-Lagunas, F. 1997. J. Physiol. 499:3–15; Gómez-Lagunas, F. 2001. J. Gen. Physiol. 118:639–648), and that channel block by TEAo and scorpion toxins are two mutually exclusive events (Goldstein, S.A.N., and C. Miller. 1993. Biophys. J. 65:1613–1619). Therefore, we tested the ability of scorpion toxins to inhibit the collapse of GK in 0 K+. We have found that these toxins are not uniform regarding the capacity to protect GK. Those toxins, whose binding to the channels is destabilized by external K+, are also effective inhibitors of the collapse of GK. In addition to K+, other externally added cations also destabilize toxin block, with an effectiveness that does not match the selectivity sequence of K+ channels. The inhibition of the drop of GK follows a saturation relationship with [toxin], which is fitted well by the Michaelis-Menten equation, with an apparent Kd bigger than that of block of the K+ current. However, another plausible model is also presented and compared with the Michaelis-Menten model. The observations suggest that those toxins that protect GK in 0 K+ do so by interacting either with the most external K+ binding site of the selectivity filter (suggesting that the K+ occupancy of only that site of the pore may be enough to preserve GK) or with sites capable of binding K+ located in the outer vestibule of the pore, above the selectivity filter.

scholarly journals The Tetrodotoxin Binding Site Is within the Outer Vestibule of the Sodium Channel

Marine Drugs ◽  
2010 ◽  
Vol 8 (2) ◽  
pp. 219-234 ◽  
Author(s):  
Harry A. Fozzard ◽  
Gregory M. Lipkind
Keyword(s):  
Sodium Channel ◽  
Binding Site ◽  
Outer Vestibule

scholarly journals The High-Affinity Binding Site for Tricyclic Antidepressants Resides in the Outer Vestibule of the Serotonin Transporter

2010 ◽  
Vol 78 (6) ◽  
pp. 1026-1035 ◽  
Author(s):  
Subhodeep Sarker ◽  
René Weissensteiner ◽  
Ilka Steiner ◽  
Harald H. Sitte ◽  
Gerhard F. Ecker ◽  
...  
Keyword(s):  
Binding Site ◽  
Serotonin Transporter ◽  
Tricyclic Antidepressants ◽  
Affinity Binding ◽  
High Affinity Binding ◽  
High Affinity ◽  
Outer Vestibule ◽  
High Affinity Binding Site

scholarly journals Influence of Pore Residues on Permeation Properties in the Kv2.1 Potassium Channel. Evidence for a Selective Functional Interaction of K+ with the Outer Vestibule

2003 ◽  
Vol 121 (2) ◽  
pp. 111-124 ◽  
Author(s):  
Joseph F. Consiglio ◽  
Payam Andalib ◽  
Stephen J. Korn
Keyword(s):  
Potassium Channel ◽  
Binding Site ◽  
Outward Current ◽  
Selectivity Filter ◽  
Structural Basis ◽  
K Channels ◽  
Local Energy Minimum ◽  
Current Magnitude ◽  
Outer Vestibule ◽  
Permeation Properties

The Kv2.1 potassium channel contains a lysine in the outer vestibule (position 356) that markedly reduces open channel sensitivity to changes in external [K+]. To investigate the mechanism underlying this effect, we examined the influence of this outer vestibule lysine on three measures of K+ and Na+ permeation. Permeability ratio measurements, measurements of the lowest [K+] required for interaction with the selectivity filter, and measurements of macroscopic K+ and Na+ conductance, were all consistent with the same conclusion: that the outer vestibule lysine in Kv2.1 interferes with the ability of K+ to enter or exit the extracellular side of the selectivity filter. In contrast to its influence on K+ permeation properties, Lys 356 appeared to be without effect on Na+ permeation. This suggests that Lys 356 limited K+ flux by interfering with a selective K+ binding site. Combined with permeation studies, results from additional mutagenesis near the external entrance to the selectivity filter indicated that this site was located external to, and independent from, the selectivity filter. Protonation of a naturally occurring histidine in the same outer vestibule location in the Kv1.5 potassium channel produced similar effects on K+ permeation properties. Together, these results indicate that a selective, functional K+ binding site (e.g., local energy minimum) exists in the outer vestibule of voltage-gated K+ channels. We suggest that this site is the location of K+ hydration/dehydration postulated to exist based on the structural studies of KcsA. Finally, neutralization of position 356 enhanced outward K+ current magnitude, but did not influence the ability of internal K+ to enter the pore. These data indicate that in Kv2.1, exit of K+ from the selectivity filter, rather than entry of internal K+ into the channel, limits outward current magnitude. We discuss the implications of these findings in relation to the structural basis of channel conductance in different K+ channels.

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