scholarly journals Cryo-EM structure of a proton-activated chloride channel TMEM206

2021 ◽  
Vol 7 (9) ◽  
pp. eabe5983
Author(s):  
Zengqin Deng ◽  
Yonghui Zhao ◽  
Jing Feng ◽  
Jingying Zhang ◽  
Haiyan Zhao ◽  
...  
Keyword(s):  
Chloride Channel ◽  
Chloride Channels ◽  
Ion Selectivity ◽  
Chloride Ion ◽  
Transmembrane Segments ◽  
New Class ◽  
The Core ◽  
Cryo Electron Microscopy ◽  
Extracellular Region ◽  
Evolutionarily Conserved

TMEM206 has been recently identified as an evolutionarily conserved chloride channel that underlies ubiquitously expressed, proton-activated, outwardly rectifying anion currents. Here, we report the cryo–electron microscopy structure of pufferfish TMEM206, which forms a trimeric channel, with each subunit comprising two transmembrane segments and a large extracellular domain. An ample vestibule in the extracellular region is accessible laterally from the three side portals. The central pore contains multiple constrictions. A conserved lysine residue near the cytoplasmic end of the inner helix forms the presumed chloride ion selectivity filter. Unprecedentedly, the core structure and assembly closely resemble those of the epithelial sodium channel/degenerin family of sodium channels that are unrelated in amino acid sequence and conduct cations instead of anions. Together with electrophysiology, this work provides insights into ion conduction and gating for a new class of chloride channels that is architecturally distinct from previously characterized chloride channel families.

scholarly journals Cryo-EM structure of a proton-activated chloride channel TMEM206

2020 ◽  
Author(s):  
Zengqin Deng ◽  
Yonghui Zhao ◽  
Jing Feng ◽  
Jingying Zhang ◽  
Haiyan Zhao ◽  
...  
Keyword(s):  
Chloride Channel ◽  
Chloride Channels ◽  
Ion Selectivity ◽  
Chloride Ion ◽  
Ion Conduction ◽  
Transmembrane Segments ◽  
New Class ◽  
Cryo Electron Microscopy ◽  
Extracellular Region ◽  
Evolutionarily Conserved

AbstractTMEM206 has been recently identified as an evolutionarily conserved chloride channel that underlies ubiquitously expressed, proton-activated, outwardly rectifying anion currents. Here we report the cryo-electron microscopy structure of pufferfish TMEM206, which forms a trimeric channel, with each subunit comprising two transmembrane segments, the outer and inner helices, and a large extracellular domain. An ample vestibule in the extracellular region is accessible laterally from the three side portals. The central pore contains multiple constrictions preventing ion conduction. A conserved lysine residue near the cytoplasmic end of the inner helix forms the presumed chloride ion selectivity filter. Unprecedentedly, the core structure and assembly closely resemble those of the epithelial sodium channel/degenerin family of sodium channels that are unrelated in amino acid sequence and conduct cations instead of anions. Together with electrophysiology, this work provides insights into ion conduction and gating for a new class of chloride channels that is architecturally distinct from previously characterized chloride channel families.

scholarly journals Subdued, a TMEM16 family Ca2+-activated Cl− channel in Drosophila melanogaster with an unexpected role in host defense

eLife ◽  
2013 ◽  
Vol 2 ◽  
Author(s):  
Xiu Ming Wong ◽  
Susan Younger ◽  
Christian J Peters ◽  
Yuh Nung Jan ◽  
Lily Y Jan
Keyword(s):  
Drosophila Melanogaster ◽  
Host Defense ◽  
Chloride Channels ◽  
Pathogenic Bacteria ◽  
Ion Selectivity ◽  
Kinetic Properties ◽  
Amino Acid Substitutions ◽  
Biophysical Properties ◽  
Evolutionarily Conserved ◽  
Open Question

TMEM16A and TMEM16B are calcium-activated chloride channels (CaCCs) with important functions in mammalian physiology. Whether distant relatives of the vertebrate TMEM16 families also form CaCCs is an intriguing open question. Here we report that a TMEM16 family member from Drosophila melanogaster, Subdued (CG16718), is a CaCC. Amino acid substitutions of Subdued alter the ion selectivity and kinetic properties of the CaCC channels heterologously expressed in HEK 293T cells. This Drosophila channel displays characteristics of classic CaCCs, thereby providing evidence for evolutionarily conserved biophysical properties in the TMEM16 family. Additionally, we show that knockout flies lacking subdued gene activity more readily succumb to death caused by ingesting the pathogenic bacteria Serratia marcescens, suggesting that subdued has novel functions in Drosophila host defense.

scholarly journals Structures of Rhodopseudomonas palustris RC-LH1 complexes with open or closed quinone channels

2021 ◽  
Vol 7 (3) ◽  
pp. eabe2631
Author(s):  
David J. K. Swainsbury ◽  
Pu Qian ◽  
Philip J. Jackson ◽  
Kaitlyn M. Faries ◽  
Dariusz M. Niedzwiedzki ◽  
...  
Keyword(s):  
Binding Sites ◽  
Rhodopseudomonas Palustris ◽  
Ring Closure ◽  
Light Harvesting Complex ◽  
The Core ◽  
Quinone Binding ◽  
Cryo Electron Microscopy ◽  
Unique Protein ◽  
Center Light ◽  
Resolution Structure

The reaction-center light-harvesting complex 1 (RC-LH1) is the core photosynthetic component in purple phototrophic bacteria. We present two cryo–electron microscopy structures of RC-LH1 complexes from Rhodopseudomonas palustris. A 2.65-Å resolution structure of the RC-LH114-W complex consists of an open 14-subunit LH1 ring surrounding the RC interrupted by protein-W, whereas the complex without protein-W at 2.80-Å resolution comprises an RC completely encircled by a closed, 16-subunit LH1 ring. Comparison of these structures provides insights into quinone dynamics within RC-LH1 complexes, including a previously unidentified conformational change upon quinone binding at the RC QB site, and the locations of accessory quinone binding sites that aid their delivery to the RC. The structurally unique protein-W prevents LH1 ring closure, creating a channel for accelerated quinone/quinol exchange.

Relative contribution of different transmembrane segments to the CFTR chloride channel pore

2013 ◽  
Vol 466 (3) ◽  
pp. 477-490 ◽  
Author(s):  
Wuyang Wang ◽  
Yassine El Hiani ◽  
Hussein N. Rubaiy ◽  
Paul Linsdell
Keyword(s):  
Chloride Channel ◽  
Channel Pore ◽  
Transmembrane Segments ◽  
Relative Contribution

scholarly journals The Role of Serum Chloride in Acute and Chronic Heart Failure: A Narrative Review

2021 ◽  
Vol 11 (2) ◽  
pp. 87-98
Author(s):  
Frederick Berro Rivera ◽  
Pia Alfonso ◽  
Jem Marie Golbin ◽  
Kevin Lo ◽  
Edgar Lerma ◽  
...  
Keyword(s):  
Heart Failure ◽  
Chloride Channel ◽  
Chloride Channels ◽  
Prognostic Value ◽  
Diuretic Therapy ◽  
Juxtaglomerular Apparatus ◽  
Sodium Chloride Cotransporter ◽  
Serum Chloride ◽  
And Function

Clinical guidelines include diuretics for the treatment of heart failure (HF), not to decrease mortality but to decrease symptoms and hospitalizations. More attention has been paid to the worse outcomes, including mortality, associated with continual diuretic therapy due to hypochloremia. Studies have revealed a pivotal role for serum chloride in the pathophysiology of HF and is now a target of treatment to decrease mortality. The prognostic value of serum chloride in HF has been the subject of much attention. Mechanistically, the macula densa, a region in the renal juxtaglomerular apparatus, relies on chloride levels to sense salt and volume status. The recent discovery of with-no-lysine (K) (WNK) protein kinase as an intracellular chloride sensor sheds light on the possible reason of diuretic resistance in HF. The action of chloride on WNKs results in the upregulation of the sodium-potassium-chloride cotransporter and sodium-chloride cotransporter receptors, which could lead to increased electrolyte and fluid reabsorption. Genetic studies have revealed that a variant of a voltage-sensitive chloride channel (CLCNKA) gene leads to almost a 50% decrease in current amplitude and function of the renal chloride channel. This variant increases the risk of HF. Several trials exploring the prognostic value of chloride in both acute and chronic HF have shown mostly positive results, some even suggesting a stronger role than sodium. However, so far, interventional trials exploring serum chloride as a therapeutic target have been largely inconclusive. This study is a review of the pathophysiologic effects of hypochloremia in HF, the genetics of chloride channels, and clinical trials that are underway to investigate novel approaches to HF management.

scholarly journals mtCLIC/CLIC4, an Organellular Chloride Channel Protein, Is Increased by DNA Damage and Participates in the Apoptotic Response to p53

2002 ◽  
Vol 22 (11) ◽  
pp. 3610-3620 ◽  
Author(s):  
Ester Fernández-Salas ◽  
Kwang S. Suh ◽  
Vladislav V. Speransky ◽  
Wendy L. Bowers ◽  
Joshua M. Levy ◽  
...  
Keyword(s):  
Dna Damage ◽  
Chloride Channel ◽  
Chloride Channels ◽  
Mitochondrial Membrane ◽  
Cellular Response ◽  
Mitochondrial Protein ◽  
Inner Mitochondrial Membrane ◽  
Necrosis Factor Alpha ◽  
Channel Protein ◽  
Factor Alpha

ABSTRACT mtCLIC/CLIC4 (referred to here as mtCLIC) is a p53- and tumor necrosis factor alpha-regulated cytoplasmic and mitochondrial protein that belongs to the CLIC family of intracellular chloride channels. mtCLIC associates with the inner mitochondrial membrane. Dual regulation of mtCLIC by two stress response pathways suggested that this chloride channel protein might contribute to the cellular response to cytotoxic stimuli. DNA damage or overexpression of p53 upregulates mtCLIC and induces apoptosis. Overexpression of mtCLIC by transient transfection reduces mitochondrial membrane potential, releases cytochrome c into the cytoplasm, activates caspases, and induces apoptosis. mtCLIC is additive with Bax in inducing apoptosis without a physical association of the two proteins. Antisense mtCLIC prevents the increase in mtCLIC levels and reduces apoptosis induced by p53 but not apoptosis induced by Bax, suggesting that the two proapoptotic proteins function through independent pathways. Our studies indicate that mtCLIC, like Bax, Noxa, p53AIP1, and PUMA, participates in a stress-induced death pathway converging on mitochondria and should be considered a target for cancer therapy through genetic or pharmacologic approaches.

scholarly journals Flaviviruses have imperfect icosahedral symmetry

2018 ◽  
Vol 115 (45) ◽  
pp. 11608-11612 ◽  
Author(s):  
Matthew D. Therkelsen ◽  
Thomas Klose ◽  
Frank Vago ◽  
Wen Jiang ◽  
Michael G. Rossmann ◽  
...  
Keyword(s):  
Lipid Membrane ◽  
Viral Assembly ◽  
Icosahedral Symmetry ◽  
Proximal Pole ◽  
The Core ◽  
Cryo Electron Microscopy ◽  
Symmetry Constraints ◽  
Conformational Rearrangements ◽  
Mature Virus ◽  
Concentric Organization

Flaviviruses assemble initially in an immature, noninfectious state and undergo extensive conformational rearrangements to generate mature virus. Previous cryo-electron microscopy (cryo-EM) structural studies of flaviviruses assumed icosahedral symmetry and showed the concentric organization of the external glycoprotein shell, the lipid membrane, and the internal nucleocapsid core. We show here that when icosahedral symmetry constraints were excluded in calculating the cryo-EM reconstruction of an immature flavivirus, the nucleocapsid core was positioned asymmetrically with respect to the glycoprotein shell. The core was positioned closer to the lipid membrane at the proximal pole, and at the distal pole, the outer glycoprotein spikes and inner membrane leaflet were either perturbed or missing. In contrast, in the asymmetric reconstruction of a mature flavivirus, the core was positioned concentric with the glycoprotein shell. The deviations from icosahedral symmetry demonstrated that the core and glycoproteins have varied interactions, which likely promotes viral assembly and budding.

scholarly journals GhCLCg-1, a Vacuolar Chloride Channel, Contributes to Salt Tolerance by Regulating Ion Accumulation in Upland Cotton

2021 ◽  
Vol 12 ◽  
Author(s):  
Wei Liu ◽  
Junping Feng ◽  
Wenyu Ma ◽  
Yang Zhou ◽  
Zongbin Ma
Keyword(s):  
Salt Tolerance ◽  
Chloride Channel ◽  
Upland Cotton ◽  
Chloride Ion ◽  
Ion Accumulation ◽  
Affected Plant ◽  
Gene Expression Analyses ◽  
Stems And Leaves ◽  
Cbs Domains ◽  
Freshwater Salinization

Soil and freshwater salinization is increasingly becoming a problem worldwide and has adversely affected plant growth. However, most of the related studies have focused on sodium ion (Na+) stress, with relatively little research on chloride ion (Cl–) stress. Here, we found that upland cotton (Gossypium hirsutum) plants accumulated Cl– and exhibited strong growth inhibition under NaCl or KCl treatment. Then, a chloride channel gene (GhCLCg-1) was cloned from upland cotton. Phylogenetic and sequence analyses indicated that GhCLCg-1 was highly homologous to AtCLCg and also have conserved voltage_CLC and CBS domains. The subcellular localization assay showed that GhCLCg-1 was localized on the vacuolar membrane. Gene expression analyses revealed that the expression of GhCLCg-1 increased rapidly in cotton in response to chloride stress (NaCl or KCl), and the transcript levels increased as the chloride stress intensified. The overexpression of GhCLCg-1 in Arabidopsis thaliana changed the uptake of ions with a decrease of the Na+/K+ ratios in the roots, stems, and leaves, and enhanced salt tolerance. In contrast, silencing GhCLCg-1 in cotton plants increased the Cl– contents in the roots, stems, and leaves and the Na+/K+ ratios in the stems and leaves, resulting in compromised salt tolerance. These results provide important insights into the toxicity of chloride to plants and also indicate that GhCLCg-1 can positively regulates salt tolerance by adjusting ion accumulation in upland cotton.

scholarly journals Assisted assembly of bacteriophage T7 core components for genome translocation across the bacterial envelope

2021 ◽  
Vol 118 (34) ◽  
pp. e2026719118
Author(s):  
Mar Pérez-Ruiz ◽  
Mar Pulido-Cid ◽  
Juan Román Luque-Ortega ◽  
José María Valpuesta ◽  
Ana Cuervo ◽  
...  
Keyword(s):  
Bacteriophage T7 ◽  
Dna Translocation ◽  
Oligomeric State ◽  
Viral Dna ◽  
The Core ◽  
Cryo Electron Microscopy ◽  
Core Proteins ◽  
Core Components ◽  
Bacterial Cytoplasm ◽  
Bacterial Peptidoglycan

In most bacteriophages, genome transport across bacterial envelopes is carried out by the tail machinery. In viruses of the Podoviridae family, in which the tail is not long enough to traverse the bacterial wall, it has been postulated that viral core proteins assembled inside the viral head are translocated and reassembled into a tube within the periplasm that extends the tail channel. Bacteriophage T7 infects Escherichia coli, and despite extensive studies, the precise mechanism by which its genome is translocated remains unknown. Using cryo-electron microscopy, we have resolved the structure of two different assemblies of the T7 DNA translocation complex composed of the core proteins gp15 and gp16. Gp15 alone forms a partially folded hexamer, which is further assembled upon interaction with gp16 into a tubular structure, forming a channel that could allow DNA passage. The structure of the gp15–gp16 complex also shows the location within gp16 of a canonical transglycosylase motif involved in the degradation of the bacterial peptidoglycan layer. This complex docks well in the tail extension structure found in the periplasm of T7-infected bacteria and matches the sixfold symmetry of the phage tail. In such cases, gp15 and gp16 that are initially present in the T7 capsid eightfold-symmetric core would change their oligomeric state upon reassembly in the periplasm. Altogether, these results allow us to propose a model for the assembly of the core translocation complex in the periplasm, which furthers understanding of the molecular mechanism involved in the release of T7 viral DNA into the bacterial cytoplasm.

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