scholarly journals Desensitization of NMDA channels requires ligand binding to both GluN1 and GluN2 subunits to constrict the pore beside the activation gate

2019 ◽  
Vol 153 (5) ◽  
pp. 549-566
Author(s):  
Yu‐Shian Chen ◽  
Ya‐Chi Tu ◽  
Yi‐Chen Lai ◽  
Erin Liu ◽  
Ya‐Chin Yang ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Activation Gate ◽  
Nmda Channels

scholarly journals Inner activation gate in S6 contributes to the state-dependent binding of cAMP in full-length HCN2 channel

2012 ◽  
Vol 140 (1) ◽  
pp. 29-39 ◽  
Author(s):  
Shengjun Wu ◽  
Weihua Gao ◽  
Changan Xie ◽  
Xinping Xu ◽  
Christina Vorvis ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Cyclic Nucleotide ◽  
Binding Domain ◽  
Hcn Channels ◽  
Channel Blockers ◽  
Structural Elements ◽  
Hcn Channel ◽  
Channel Interaction ◽  
State Dependent ◽  
Activation Gate

Recently, applications of the patch-clamp fluorometry (PCF) technique in studies of cyclic nucleotide–gated (CNG) and hyperpolarization-activated, cyclic nucleotide–regulated (HCN) channels have provided direct evidence for the long-held notion that ligands preferably bind to and stabilize these channels in an open state. This state-dependent ligand–channel interaction involves contributions from not only the ligand-binding domain but also other discrete structural elements within the channel protein. This insight led us to investigate whether the pore of the HCN channel plays a role in the ligand–whole channel interaction. We used three well-characterized HCN channel blockers to probe the ion-conducting passage. The PCF technique was used to simultaneously monitor channel activity and cAMP binding. Two ionic blockers, Cs+ and Mg2+, effectively block channel conductance but have no obvious effect on cAMP binding. Surprisingly, ZD7288, an open channel blocker specific for HCN channels, significantly reduces the activity-dependent increase in cAMP binding. Independent biochemical assays exclude any nonspecific interaction between ZD7288 and isolated cAMP-binding domain. Because ZD7228 interacts with the inner pore region, where the activation gate is presumably located, we did an alanine scanning of the intracellular end of S6, from T426 to A435. Mutations of three residues, T426, M430, and H434, which are located at regular intervals on the S6 α-helix, enhance cAMP binding. In contrast, mutations of two residues in close proximity, F431A and I432A, dampen the response. Our results demonstrate that movements of the structural elements near the activation gate directly affect ligand binding affinity, which is a simple mechanistic explanation that could be applied to the interpretation of ligand gating in general.

scholarly journals hERG S4-S5 acts as a Voltage-Dependent Ligand Binding the Activation Gate and Locking it in a Closed State

2016 ◽  
Vol 110 (3) ◽  
pp. 278a
Author(s):  
Olfat Malak ◽  
Gildas Loussouarn ◽  
Zeineb Es-Salah-Lamoureux
Keyword(s):  
Ligand Binding ◽  
Closed State ◽  
Activation Gate ◽  
Voltage Dependent

CarR, a MarR-family regulator from Corynebacterium glutamicum, modulated antibiotic and aromatic compound resistance

2019 ◽  
Vol 476 (21) ◽  
pp. 3141-3159 ◽  
Author(s):  
Meiru Si ◽  
Can Chen ◽  
Zengfan Wei ◽  
Zhijin Gong ◽  
GuiZhi Li ◽  
...  
Keyword(s):  
Stress Response ◽  
Ligand Binding ◽  
Corynebacterium Glutamicum ◽  
Conformational Changes ◽  
Cysteine Oxidation ◽  
Transcriptional Regulatory ◽  
Ligand Free ◽  
Redox Sensing

Abstract MarR (multiple antibiotic resistance regulator) proteins are a family of transcriptional regulators that is prevalent in Corynebacterium glutamicum. Understanding the physiological and biochemical function of MarR homologs in C. glutamicum has focused on cysteine oxidation-based redox-sensing and substrate metabolism-involving regulators. In this study, we characterized the stress-related ligand-binding functions of the C. glutamicum MarR-type regulator CarR (C. glutamicum antibiotic-responding regulator). We demonstrate that CarR negatively regulates the expression of the carR (ncgl2886)–uspA (ncgl2887) operon and the adjacent, oppositely oriented gene ncgl2885, encoding the hypothetical deacylase DecE. We also show that CarR directly activates transcription of the ncgl2882–ncgl2884 operon, encoding the peptidoglycan synthesis operon (PSO) located upstream of carR in the opposite orientation. The addition of stress-associated ligands such as penicillin and streptomycin induced carR, uspA, decE, and PSO expression in vivo, as well as attenuated binding of CarR to operator DNA in vitro. Importantly, stress response-induced up-regulation of carR, uspA, and PSO gene expression correlated with cell resistance to β-lactam antibiotics and aromatic compounds. Six highly conserved residues in CarR were found to strongly influence its ligand binding and transcriptional regulatory properties. Collectively, the results indicate that the ligand binding of CarR induces its dissociation from the carR–uspA promoter to derepress carR and uspA transcription. Ligand-free CarR also activates PSO expression, which in turn contributes to C. glutamicum stress resistance. The outcomes indicate that the stress response mechanism of CarR in C. glutamicum occurs via ligand-induced conformational changes to the protein, not via cysteine oxidation-based thiol modifications.

Exploration of the peptide ligand-binding domain of the motilin receptor using photoaffinity labeling and receptor mutagenesis

2001 ◽  
Vol 120 (5) ◽  
pp. A509-A509
Author(s):  
B MATSUURA ◽  
M DONG ◽  
B COULIE ◽  
E HADAC ◽  
D PINON ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Photoaffinity Labeling ◽  
Binding Domain ◽  
Ligand Binding Domain ◽  
Peptide Ligand ◽  
Motilin Receptor

TBG MEASUREMENTS BY COMPETITIVE LIGAND BINDING ASSAY (CLBA)

1975 ◽  
Vol 80 (1_Suppla) ◽  
pp. S15
Author(s):  
K. H. Rudorff ◽  
H. J. Kröll ◽  
J. Herrmann
Keyword(s):  
Ligand Binding ◽  
Binding Assay ◽  
Ligand Binding Assay ◽  
Competitive Ligand

Constraints of Opsin Structure on the Ligand-binding Site: Studies with Ring-fused Retinals¶

2002 ◽  
Vol 76 (6) ◽  
pp. 606 ◽  
Author(s):  
Takahiro Hirano ◽  
In Taek Lim ◽  
Don Moon Kim ◽  
Xiang-Guo Zheng ◽  
Kazuo Yoshihara ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Binding Site ◽  
Ligand Binding Site
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