scholarly journals The Polyamine Binding Site in Inward Rectifier K+ Channels

2006 ◽  
Vol 127 (5) ◽  
pp. 467-480 ◽  
Author(s):  
Harley T. Kurata ◽  
Laurence J. Marton ◽  
Colin G. Nichols
Keyword(s):  
Binding Site ◽  
Exit Rate ◽  
Physical Constraints ◽  
Kir Channel ◽  
Inwardly Rectifying Potassium Channels ◽  
Voltage Dependent ◽  
Deep Site ◽  
Inwardly Rectifying ◽  
Polyamine Binding Site ◽  
Deep Location

Strongly inwardly rectifying potassium channels exhibit potent and steeply voltage-dependent block by intracellular polyamines. To locate the polyamine binding site, we have examined the effects of polyamine blockade on the rate of MTSEA modification of cysteine residues strategically substituted in the pore of a strongly rectifying Kir channel (Kir6.2[N160D]). Spermine only protected cysteines substituted at a deep location in the pore, between the “rectification controller” residue (N160D in Kir6.2, D172 in Kir2.1) and the selectivity filter, against MTSEA modification. In contrast, blockade with a longer synthetic polyamine (CGC-11179) also protected cysteines substituted at sites closer to the cytoplasmic entrance of the channel. Modification of a cysteine at the entrance to the inner cavity (169C) was unaffected by either spermine or CGC-11179, and spermine was clearly “locked” into the inner cavity (i.e., exhibited a dramatically slower exit rate) following modification of this residue. These data provide physical constraints on the spermine binding site, demonstrating that spermine stably binds at a deep site beyond the “rectification controller” residue, near the extracellular entrance to the channel.

Block of inwardly rectifying K+ currents by extracellular Mg2+ and Ba2+ in bovine pulmonary artery endothelial cells

2000 ◽  
Vol 78 (9) ◽  
pp. 751-756 ◽  
Author(s):  
Yuk Man Leung ◽  
Chiu Yin Kwan ◽  
Edwin E Daniel
Keyword(s):  
Endothelial Cells ◽  
Patch Clamp ◽  
Pulmonary Artery ◽  
Binding Site ◽  
Patch Clamp Technique ◽  
Aortic Endothelial Cells ◽  
Whole Cell Patch Clamp ◽  
Deep Site ◽  
Low Sensitivity ◽  
Inwardly Rectifying

Using whole-cell patch clamp technique, we investigated the blocking effects of extracellular Ba2+ and Mg2+ on the inwardly rectifying K+ (KIR) currents of bovine pulmonary artery endothelial cells (BPAEC). The BPAEC KIR channel has recently been identified as Kir2.1 of the Kir2.0 subfamily. Block of KIR currents by Mg2+ (3-30 mM) was instantaneous, and increased with hyperpolarization slightly (Kd at -160 and 0 mV was 9.5 and 23.2 mM, respectively). The apparent fractional electrical distance (δ) of the Mg2+ binding site is calculated to be 0.07 from the outer mouth of the channel pore. Ba2+ (0.3-10 µM) time-dependently blocked the KIR currents with a much higher potency and stronger voltage-dependence (Kd at -160 and 0 mV was 1.0 and 41.6 µM, respectively). The Ba2+ binding site had a δ value of 0.34. Our data suggest that Mg2+ binds to a very superficial site of the KIR channel, while Ba2+ binds to a much deeper site, sensing much more of the membrane electric field. Thus, the BPAEC Kir2.1 appears to be pharmacologically different from the Kir2.1 reported before in bovine aortic endothelial cells (BAEC), which has 2 sites for Mg2+ block (a deep site in addition to a shallow one), and a superficial and low-sensitivity site for Ba2+ block.Key words: inwardly rectifying K+ channel, patch clamp, Ba2+, Mg2+, endothelial cells.

scholarly journals Unconventional voltage sensing in an inwardly rectifying potassium channel

2021 ◽  
Vol 153 (6) ◽  
Author(s):  
Harley T. Kurata
Keyword(s):  
Potassium Channels ◽  
Potassium Channel ◽  
Voltage Dependence ◽  
Voltage Sensing ◽  
Inwardly Rectifying Potassium Channel ◽  
Inwardly Rectifying Potassium Channels ◽  
Voltage Dependent ◽  
Inwardly Rectifying ◽  
Surprising Finding ◽  
Heteromeric Channels

Inwardly rectifying potassium channels are generally thought to achieve their physiological voltage dependence via an “extrinsic” mechanism involving voltage-dependent block by polyamines. A surprising finding of polyamine-independent gating of Kir4.1/Kir5.1 heteromeric channels suggests a mechanism of voltage dependence arising from interactions with permeating ions.

scholarly journals Naringin directly activates inwardly rectifying potassium channels at an overlapping binding site to tertiapin-Q

2011 ◽  
Vol 163 (5) ◽  
pp. 1017-1033 ◽  
Author(s):  
Tin T Yow ◽  
Elena Pera ◽  
Nathan Absalom ◽  
Marika Heblinski ◽  
Graham AR Johnston ◽  
...  
Keyword(s):  
Potassium Channels ◽  
Binding Site ◽  
Inwardly Rectifying Potassium Channels ◽  
Inwardly Rectifying

scholarly journals Locale and chemistry of spermine binding in the archetypal inward rectifier Kir2.1

2010 ◽  
Vol 135 (5) ◽  
pp. 495-508 ◽  
Author(s):  
Harley T. Kurata ◽  
Emily A. Zhu ◽  
Colin G. Nichols
Keyword(s):  
Binding Site ◽  
Voltage Dependence ◽  
Inward Rectifier ◽  
Selectivity Filter ◽  
Inward Rectification ◽  
Before And After ◽  
Voltage Dependent ◽  
Inwardly Rectifying ◽  
Kinetics Of

Polyamine block of inwardly rectifying potassium (Kir) channels underlies their steep voltage dependence observed in vivo. We have examined the potency, voltage dependence, and kinetics of spermine block in dimeric Kir2.1 constructs containing one nonreactive subunit and one cysteine-substituted subunit before and after modification by methanethiosulfonate (MTS) reagents. At position 169C (between the D172 “rectification controller” and the selectivity filter), modification by either 2-aminoethyl MTS (MTSEA) or 2-(trimethylammonium)ethyl MTS (MTSET) reduced the potency and voltage dependence of spermine block, consistent with this position overlapping the spermine binding site. At position 176C (between D172 and the M2 helix bundle crossing), modification by MTSEA also weakened spermine block. In contrast, MTSET modification of 176C dramatically slowed the kinetics of spermine unblock, with almost no effect on potency or voltage dependence. The data are consistent with MTSET modification of 176C introducing a localized barrier in the inner cavity, resulting in slower spermine entry into and exit from a “deep” binding site (likely between the D172 rectification controller and the selectivity filter), but leaving the spermine binding site mostly unaffected. These findings constrain the location of deep spermine binding that underlies steeply voltage-dependent block, and further suggest important chemical details of high affinity binding of spermine in Kir2.1 channels—the archetypal model of strong inward rectification.

scholarly journals Gating Sensitive Residues In The Pore Of An Inwardly Rectifying Potassium (Kir) Channel

2009 ◽  
Vol 96 (3) ◽  
pp. 462a
Author(s):  
Murali K. Bollepalli ◽  
Markus Rapedius ◽  
Philip Fowler ◽  
Man-Jiang Xie ◽  
Lijun Shang ◽  
...  
Keyword(s):  
Kir Channel ◽  
Inwardly Rectifying
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