scholarly journals Structural and Functional Consequences of an Amide-to-Ester Substitution in the Selectivity Filter of a Potassium Channel

2006 ◽  
Vol 128 (35) ◽  
pp. 11591-11599 ◽  
Author(s):  
Francis I. Valiyaveetil ◽  
Matthew Sekedat ◽  
Roderick MacKinnon ◽  
Tom W. Muir
Keyword(s):  
Potassium Channel ◽  
Selectivity Filter ◽  
Functional Consequences

scholarly journals Functional Consequences of a Decreased Potassium Affinity in a Potassium Channel Pore

1999 ◽  
Vol 113 (2) ◽  
pp. 347-358 ◽  
Author(s):  
Eva M. Ogielska ◽  
Richard W. Aldrich
Keyword(s):  
Potassium Channel ◽  
Binding Site ◽  
Conformational Change ◽  
Electrostatic Interactions ◽  
Selectivity Filter ◽  
Inactivation Rate ◽  
Ion Binding ◽  
Present Evidence ◽  
Channel Pore ◽  
Functional Consequences

Ions bound near the external mouth of the potassium channel pore impede the C-type inactivation conformational change (Lopez-Barneo, J., T. Hoshi, S. Heinemann, and R. Aldrich. 1993. Receptors Channels. 1:61– 71; Baukrowitz, T., and G. Yellen. 1995. Neuron. 15:951–960). In this study, we present evidence that the occupancy of the C-type inactivation modulatory site by permeant ions is not solely dependent on its intrinsic affinity, but is also a function of the relative affinities of the neighboring sites in the potassium channel pore. The A463C mutation in the S6 region of Shaker decreases the affinity of an internal ion binding site in the pore (Ogielska, E.M., and R.W. Aldrich, 1998). However, we have found that this mutation also decreases the C-type inactivation rate of the channel. Our studies indicate that the C-type inactivation effects observed with substitutions at position A463 most likely result from changes in the pore occupancy of the channel, rather than a change in the C-type inactivation conformational change. We have found that a decrease in the potassium affinity of the internal ion binding site in the pore results in lowered (electrostatic) interactions among ions in the pore and as a result prolongs the time an ion remains bound at the external C-type inactivation site. We also present evidence that the C-type inactivation constriction is quite local and does not involve a general collapse of the selectivity filter. Our data indicate that in A463C potassium can bind within the selectivity filter without interfering with the process of C-type inactivation.

Sodium ions do not stabilize the selectivity filter of a potassium channel

2021 ◽  
pp. 167091
Author(s):  
Kitty Hendriks ◽  
Carl Öster ◽  
Chaowei Shi ◽  
Han Sun ◽  
Adam Lange
Keyword(s):  
Potassium Channel ◽  
Selectivity Filter ◽  
Sodium Ions

scholarly journals Potassium Channel Mutant KCNJ5 T158A Expression in HAC-15 Cells Increases Aldosterone Synthesis

Endocrinology ◽  
2012 ◽  
Vol 153 (4) ◽  
pp. 1774-1782 ◽  
Author(s):  
Kenji Oki ◽  
Maria W. Plonczynski ◽  
Milay Luis Lam ◽  
Elise P. Gomez-Sanchez ◽  
Celso E. Gomez-Sanchez
Keyword(s):  
Potassium Channel ◽  
Primary Aldosteronism ◽  
Calcium Influx ◽  
Fold Increase ◽  
Transitional Zone ◽  
Selectivity Filter ◽  
Adrenal Cortical Carcinoma ◽  
Aldosterone Secretion ◽  
Familial Hyperaldosteronism ◽  
Type 3

Primary aldosteronism is the most common cause of secondary hypertension, most frequently due to an aldosterone-producing adenoma or idiopathic hyperaldosteronism. Somatic mutations of the potassium channel KCNJ5 in the region of the selectivity filter have been found in a significant number of aldosterone-producing adenomas. There are also familial forms of primary aldosteronism, one of which, familial hyperaldosteronism type 3 which to date has been found in one family who presented with a severe abnormality in aldosterone and 18-oxocortisol production and hypertrophy and hyperplasia of the transitional zone of the adrenal cortex. In familial hyperaldosteronism type 3, there is a genomic mutation causing a T158A change of amino acids within the selectivity filter region of the KCNJ5 gene. We are reporting our studies demonstrating that lentiviral-mediated expression of a gene carrying the T158A mutation of the KCNJ5 in the HAC15 adrenal cortical carcinoma cell line causes a 5.3-fold increase in aldosterone secretion in unstimulated HAC15-KCNJ5 cells and that forskolin-stimulated aldosterone secretion was greater than that of angiotensin II. Expression of the mutated KCNJ5 gene decreases plasma membrane polarization, allowing sodium and calcium influx into the cells. The calcium channel antagonist nifedipine and the calmodulin inhibitor W-7 variably inhibited the effect. Overexpression of the mutated KCNJ5 channel resulted in a modest decrease in HAC15 cell proliferation. These studies demonstrate that the T158A mutation of the KCNJ5 gene produces a marked stimulation in aldosterone biosynthesis that is dependent on membrane depolarization and sodium and calcium influx into the HAC15 adrenal cortical carcinoma cells.

scholarly journals Potassium channel selectivity filter dynamics revealed by single-molecule FRET

2019 ◽  
Vol 15 (4) ◽  
pp. 377-383 ◽  
Author(s):  
Shizhen Wang ◽  
Sun-Joo Lee ◽  
Grigory Maksaev ◽  
Xin Fang ◽  
Chong Zuo ◽  
...  
Keyword(s):  
Potassium Channel ◽  
Single Molecule ◽  
Selectivity Filter ◽  
Single Molecule Fret ◽  
Channel Selectivity

scholarly journals Two Ways To Convert a Low-Affinity Potassium Channel to High Affinity: Control of Bacillus subtilis KtrCD by Glutamate

2020 ◽  
Vol 202 (12) ◽  
Author(s):  
Larissa Krüger ◽  
Christina Herzberg ◽  
Robert Warneke ◽  
Anja Poehlein ◽  
Janina Stautz ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Potassium Channel ◽  
Living Cell ◽  
Potassium Uptake ◽  
Selectivity Filter ◽  
Uptake System ◽  
Content Type ◽  
Apparent Affinity ◽  
High Affinity ◽  
External Potassium

ABSTRACT Potassium and glutamate are the major cation and anion, respectively, in every living cell. Due to the high concentrations of both ions, the cytoplasm of all cells can be regarded as a potassium glutamate solution. This implies that the concentrations of both ions need to be balanced. While the control of potassium uptake by glutamate is well established for eukaryotic cells, much less is known about the mechanisms that link potassium homeostasis to glutamate availability in bacteria. Here, we have discovered that the availability of glutamate strongly decreases the minimal external potassium concentration required for the highly abundant Bacillus subtilis potassium channel KtrCD to accumulate potassium. In contrast, the inducible KtrAB and KimA potassium uptake systems have high apparent affinities for potassium even in the absence of glutamate. Experiments with mutant strains revealed that the KtrD subunit responds to the presence of glutamate. For full activity, KtrD synergistically requires the presence of the regulatory subunit KtrC and of glutamate. The analysis of suppressor mutants of a strain that has KtrCD as the only potassium uptake system and that experiences severe potassium starvation identified a mutation in the ion selectivity filter of KtrD (Gly282 to Val) that similarly results in a strongly glutamate-independent increase of the apparent affinity for potassium. Thus, this work has identified two conditions that increase the apparent affinity of KtrCD for potassium, i.e., external glutamate and the acquisition of a single point mutation in KtrD. IMPORTANCE In each living cell, potassium is required for maintaining the intracellular pH and for the activity of essential enzymes. Like most other bacteria, Bacillus subtilis possesses multiple low- and high-affinity potassium uptake systems. Their activity is regulated by the second messenger cyclic di-AMP. Moreover, the pools of the most abundant ions potassium and glutamate must be balanced. We report two conditions under which the low-affinity potassium channel KtrCD is able to mediate potassium uptake at low external potassium concentrations: physiologically, the presence of glutamate results in a severely increased potassium uptake. Moreover, this is achieved by a mutation affecting the selectivity filter of the KtrD channel. These results highlight the integration between potassium and glutamate homeostasis in bacteria.

scholarly journals Calmodulin acts as a state-dependent switch to control a cardiac potassium channel opening

2020 ◽  
Author(s):  
Po Wei Kang ◽  
Annie M. Westerlund ◽  
Jingyi Shi ◽  
Kelli McFarland White ◽  
Alex K. Dou ◽  
...  
Keyword(s):  
Potassium Channel ◽  
Conformational Change ◽  
State Dependent ◽  
Gating Mechanism ◽  
Channel Opening ◽  
Activated State ◽  
Voltage Dependent ◽  
Functional Consequences ◽  
Pore Opening ◽  
Voltage Sensing Domain

AbstractCalmodulin (CaM) and PIP2 are potent regulators of the voltage-gated potassium channel KCNQ1 (KV7.1), which conducts the IKs current important for repolarization of cardiac action potentials. Although cryo-EM structures revealed intricate interactions between the KCNQ1 voltage-sensing domain (VSD), CaM, and PIP2, the functional consequences of these interactions remain unknown. Here, we show that CaM-VSD interactions act as a state-dependent switch to control KCNQ1 pore opening. Combined electrophysiology and molecular dynamics network analysis suggest that VSD transition into the fully-activated state allows PIP2 to compete with CaM for binding to VSD, leading to the conformational change that alters the VSD-pore coupling. We identify a motif in the KCNQ1 cytosolic domain which works downstream of CaM-VSD interactions to facilitate the conformational change. Our findings suggest a gating mechanism that integrates PIP2 and CaM in KCNQ1 voltage-dependent activation, yielding insights into how KCNQ1 gains the phenotypes critical for its function in the heart.

scholarly journals Functional Consequences of RNA Editing of the eag Potassium Channel

2009 ◽  
Vol 96 (3) ◽  
pp. 191a
Author(s):  
Mary Y. Ryan ◽  
Rachel Maloney ◽  
Robert A. Reenan ◽  
Richard Horn
Keyword(s):  
Potassium Channel ◽  
Rna Editing ◽  
Functional Consequences
Sign in / Sign up

Export Citation Format

Share Document