scholarly journals Evaluation of the membrane-spanning domain of ClC-2

2006 ◽  
Vol 396 (3) ◽  
pp. 449-460 ◽  
Author(s):  
Mohabir Ramjeesingh ◽  
Canhui Li ◽  
Yi-Min She ◽  
Christine E. Bear
Keyword(s):  
Chloride Channels ◽  
Molecular Mechanisms ◽  
Protein Structures ◽  
Idiopathic Epilepsy ◽  
Membrane Domains ◽  
Membrane Domain ◽  
Domain Boundaries ◽  
Thiol Reagent ◽  
Membrane Spanning ◽  
Prokaryotic Protein

The ClC family of chloride channels and transporters includes several members in which mutations have been associated with human disease. An understanding of the structure–function relationships of these proteins is essential for defining the molecular mechanisms underlying pathogenesis. To date, the X-ray crystal structures of prokaryotic ClC transporter proteins have been used to model the membrane domains of eukaryotic ClC channel-forming proteins. Clearly, the fidelity of these models must be evaluated empirically. In the present study, biochemical tools were used to define the membrane domain boundaries of the eukaryotic protein, ClC-2, a chloride channel mutated in cases of idiopathic epilepsy. The membrane domain boundaries of purified ClC-2 and accessible cysteine residues were determined after its functional reconstitution into proteoliposomes, labelling using a thiol reagent and proteolytic digestion. Subsequently, the lipid-embedded and soluble fragments generated by trypsin-mediated proteolysis were studied by MS and coverage of approx. 71% of the full-length protein was determined. Analysis of these results revealed that the membrane-delimited boundaries of the N- and C-termini of ClC-2 and the position of several extramembrane loops determined by these methods are largely similar to those predicted on the basis of the prokaryotic protein [ecClC (Escherichia coli ClC)] structures. These studies provide direct biochemical evidence supporting the relevance of the prokaryotic ClC protein structures towards understanding the structure of mammalian ClC channel-forming proteins.

scholarly journals Secretory granule protein chromogranin B (CHGB) forms an anion channel in membranes

2018 ◽  
Vol 1 (5) ◽  
pp. e201800139 ◽  
Author(s):  
Gaya P Yadav ◽  
Hui Zheng ◽  
Qing Yang ◽  
Lauren G Douma ◽  
Linda B Bloom ◽  
...  
Keyword(s):  
Secretory Granule ◽  
Chloride Channels ◽  
Molecular Mechanisms ◽  
Single Channel ◽  
Secretory Granules ◽  
Anion Channel ◽  
Local Concentration ◽  
Chromogranin B ◽  
Fast Kinetics ◽  
Granule Protein

Regulated secretion is an intracellular pathway that is highly conserved from protists to humans. Granin family proteins were proposed to participate in the biogenesis, maturation and release of secretory granules in this pathway. However, the exact molecular mechanisms underlying the intracellular functions of the granin family proteins remain unclear. Here, we show that chromogranin B (CHGB), a secretory granule protein, inserts itself into membrane and forms a chloride-conducting channel. CHGB interacts strongly with phospholipid membranes through two amphipathic α helices. At a high local concentration, CHGB insertion in membrane causes significant bilayer remodeling, producing protein-coated nanoparticles and nanotubules. Fast kinetics and high cooperativity for anion efflux from CHGB vesicles suggest that CHGB tetramerizes to form a functional channel with a single-channel conductance of ∼125 pS (150/150 mM Cl−). The CHGB channel is sensitive to an anion channel blocker and exhibits higher anion selectivity than the other six known families of Cl−channels. Our data suggest that the CHGB subfamily of granin proteins forms a new family of organelle chloride channels.

Modelling of Molecular Mechanisms of Membrane Domain Formation during the Oxidative Stress: Effect of Palmitoyl-oxovaleroyl-phosphatidylcholine

2021 ◽  
Author(s):  
Vesela Yordanova ◽  
Galya Staneva ◽  
Miglena Angelova ◽  
Victoria Vitkova ◽  
Aneliya Kostadinova ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Molecular Mechanisms ◽  
Stress Effect ◽  
Domain Formation ◽  
Membrane Domain

scholarly journals Mitochondrial HMG-Box Containing Proteins: From Biochemical Properties to the Roles in Human Diseases

Biomolecules ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1193 ◽  
Author(s):  
Veronika Vozáriková ◽  
Nina Kunová ◽  
Jacob A. Bauer ◽  
Ján Frankovský ◽  
Veronika Kotrasová ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Regulation Of Gene Expression ◽  
Protein Structures ◽  
High Mobility ◽  
Biochemical Properties ◽  
Structural Basis ◽  
Comprehensive Overview ◽  
Hmg Box ◽  
Mitochondrial Transcription Factor ◽  
Mitochondrial Nucleoids

Mitochondrial DNA (mtDNA) molecules are packaged into compact nucleo-protein structures called mitochondrial nucleoids (mt-nucleoids). Their compaction is mediated in part by high-mobility group (HMG)-box containing proteins (mtHMG proteins), whose additional roles include the protection of mtDNA against damage, the regulation of gene expression and the segregation of mtDNA into daughter organelles. The molecular mechanisms underlying these functions have been identified through extensive biochemical, genetic, and structural studies, particularly on yeast (Abf2) and mammalian mitochondrial transcription factor A (TFAM) mtHMG proteins. The aim of this paper is to provide a comprehensive overview of the biochemical properties of mtHMG proteins, the structural basis of their interaction with DNA, their roles in various mtDNA transactions, and the evolutionary trajectories leading to their rapid diversification. We also describe how defects in the maintenance of mtDNA in cells with dysfunctional mtHMG proteins lead to different pathologies at the cellular and organismal level.

scholarly journals Structural Similarity with Cholesterol Reveals Crucial Insights into Mechanisms Sustaining the Immunomodulatory Activity of the Mycotoxin Alternariol

Cells ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 847 ◽  
Author(s):  
Giorgia Del Favero ◽  
Raphaela M. Mayer ◽  
Luca Dellafiora ◽  
Lukas Janker ◽  
Laura Niederstaetter ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Structural Similarity ◽  
Immunomodulatory Activity ◽  
Continuous Exposure ◽  
Membrane Domains ◽  
Toll Like Receptor ◽  
Caveolin 1 ◽  
Domestic Environments ◽  
Opening Up ◽  
Immunomodulatory Potential

The proliferation of molds in domestic environments can lead to uncontrolled continuous exposure to mycotoxins. Even if not immediately symptomatic, this may result in chronic effects, such as, for instance, immunosuppression or allergenic promotion. Alternariol (AOH) is one of the most abundant mycotoxins produced by Alternaria alternata fungi, proliferating among others in fridges, as well as in humid walls. AOH was previously reported to have immunomodulatory potential. However, molecular mechanisms sustaining this effect remained elusive. In differentiated THP-1 macrophages, AOH hardly altered the secretion of pro-inflammatory mediators when co-incubated with lipopolysaccharide (LPS), opening up the possibility that the immunosuppressive potential of the toxin could be related to an alteration of a downstream pro-inflammatory signaling cascade. Intriguingly, the mycotoxin affected the membrane fluidity in macrophages and it synergistically reacted with the cholesterol binding agent MβCD. In silico modelling revealed the potential of the mycotoxin to intercalate in cholesterol-rich membrane domains, like caveolae, and immunofluorescence showed the modified interplay of caveolin-1 with Toll-like Receptor (TLR) 4. In conclusion, we identified the structural similarity with cholesterol as one of the key determinants of the immunomodulatory potential of AOH.

scholarly journals Pharmacological Overview of the BGP-15 Chemical Agent as a New Drug Candidate for the Treatment of Symptoms of Metabolic Syndrome

Molecules ◽  
2020 ◽  
Vol 25 (2) ◽  
pp. 429
Author(s):  
Ágota Pető ◽  
Dóra Kósa ◽  
Pálma Fehér ◽  
Zoltán Ujhelyi ◽  
Dávid Sinka ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Parp Inhibitor ◽  
Drug Candidate ◽  
Chemical Agent ◽  
Membrane Domains ◽  
Protective Effects ◽  
Pharmacological Effects ◽  
Research Groups ◽  
Insulin Sensitizer ◽  
Beneficial Effects

BGP-15 is a new insulin sensitizer drug candidate, which was developed by Hungarian researchers. In recent years, numerous research groups have studied its beneficial effects. It is effective in the treatment of insulin resistance and it has protective effects in Duchenne muscular dystrophy, diastolic dysfunction, tachycardia, heart failure, and atrial fibrillation, and it can alleviate cardiotoxicity. BGP-15 exhibits chemoprotective properties in different cytostatic therapies, and has also proven to be photoprotective. It can additionally have advantageous effects in mitochondrial-stress-related diseases. Although the precise mechanism of the effect is still unknown to us, we know that the molecule is a PARP inhibitor, chaperone co-inducer, reduces ROS production, and is able to remodel the organization of cholesterol-rich membrane domains. In the following review, our aim was to summarize the investigated molecular mechanisms and pharmacological effects of this potential API. The main objective was to present the wide pharmacological potentials of this chemical agent.

scholarly journals Integrated structural and evolutionary analysis reveals common mechanisms underlying adaptive evolution in mammals

2020 ◽  
Vol 117 (11) ◽  
pp. 5977-5986 ◽  
Author(s):  
Greg Slodkowicz ◽  
Nick Goldman
Keyword(s):  
Positive Selection ◽  
Adaptive Evolution ◽  
Evolutionary Biology ◽  
Molecular Mechanisms ◽  
Structural Information ◽  
Protein Structures ◽  
Unexpected Finding ◽  
Evolutionary Analysis ◽  
Genomic Scale ◽  
Evolution Of Mammals

Understanding the molecular basis of adaptation to the environment is a central question in evolutionary biology, yet linking detected signatures of positive selection to molecular mechanisms remains challenging. Here we demonstrate that combining sequence-based phylogenetic methods with structural information assists in making such mechanistic interpretations on a genomic scale. Our integrative analysis shows that positively selected sites tend to colocalize on protein structures and that positively selected clusters are found in functionally important regions of proteins, indicating that positive selection can contravene the well-known principle of evolutionary conservation of functionally important regions. This unexpected finding, along with our discovery that positive selection acts on structural clusters, opens previously unexplored strategies for the development of better models of protein evolution. Remarkably, proteins where we detect the strongest evidence of clustering belong to just two functional groups: Components of immune response and metabolic enzymes. This gives a coherent picture of pathogens and xenobiotics as important drivers of adaptive evolution of mammals.

scholarly journals Protein Machineries Involved in the Attachment of Heme to Cytochrome c: Protein Structures and Molecular Mechanisms

Scientifica ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-17 ◽  
Author(s):  
Carlo Travaglini-Allocatelli
Keyword(s):  
Molecular Mechanisms ◽  
Protein Structures ◽  
Eukaryotic Cells ◽  
Binding Motif ◽  
Gram Negative ◽  
Open Questions ◽  
Structural And Functional Properties ◽  
Cyt C ◽  
Electron Transfer Processes ◽  
Cysteine Thiols

Cytochromes c (Cyt c) are ubiquitous heme-containing proteins, mainly involved in electron transfer processes, whose structure and functions have been and still are intensely studied. Surprisingly, our understanding of the molecular mechanism whereby the heme group is covalently attached to the apoprotein (apoCyt) in the cell is still largely unknown. This posttranslational process, known as Cyt c biogenesis or Cyt c maturation, ensures the stereospecific formation of the thioether bonds between the heme vinyl groups and the cysteine thiols of the apoCyt heme binding motif. To accomplish this task, prokaryotic and eukaryotic cells have evolved distinctive protein machineries composed of different proteins. In this review, the structural and functional properties of the main maturation apparatuses found in gram-negative and gram-positive bacteria and in the mitochondria of eukaryotic cells will be presented, dissecting the Cyt c maturation process into three functional steps: (i) heme translocation and delivery, (ii) apoCyt thioreductive pathway, and (iii) apoCyt chaperoning and heme ligation. Moreover, current hypotheses and open questions about the molecular mechanisms of each of the three steps will be discussed, with special attention to System I, the maturation apparatus found in gram-negative bacteria.

scholarly journals Targeting and Stability of Na/Ca Exchanger 1 in Cardiomyocytes Requires Direct Interaction with the Membrane Adaptor Ankyrin-B

2006 ◽  
Vol 282 (7) ◽  
pp. 4875-4883 ◽  
Author(s):  
Shane R. Cunha ◽  
Naina Bhasin ◽  
Peter J. Mohler
Keyword(s):  
Molecular Mechanisms ◽  
Cardiac Tissue ◽  
Direct Interaction ◽  
Binding Activity ◽  
Membrane Domains ◽  
Excitable Cells ◽  
Expression Activity ◽  
Cellular Pathways ◽  
Ankyrin B ◽  
Calcium Extrusion

Na/Ca exchanger activity is important for calcium extrusion from the cardiomyocyte cytosol during repolarization. Animal models exhibiting altered Na/Ca exchanger expression display abnormal cardiac phenotypes. In humans, elevated Na/Ca exchanger expression/activity is linked with pathophysiological conditions including arrhythmia and heart failure. Whereas the molecular mechanisms underlying Na/Ca exchanger biophysical properties are widely studied and generally well characterized, the cellular pathways and molecular partners underlying the specialized membrane localization of Na/Ca exchanger in cardiac tissue are essentially unknown. In this report, we present the first direct evidence for a protein pathway required for Na/Ca exchanger localization and stability in primary cardiomyocytes. We define the minimal structural requirements on ankyrin-B for direct Na/Ca exchanger interactions. Moreover, using ankyrin-B mutants that lack Na/Ca exchanger binding activity, and primary cardiomyocytes with reduced ankyrin-B expression, we demonstrate that direct interaction with the membrane adaptor ankyrin-B is required for the localization and post-translational stability of Na/Ca exchanger 1 in neonatal mouse cardiomyocytes. These results raise exciting new questions regarding potentially dynamic roles for ankyrin proteins in the biogenesis and maintenance of specialized membrane domains in excitable cells.

scholarly journals Cholesterol-dependent partitioning of PtdIns(4,5)P2 into membrane domains by the N-terminal fragment of NAP-22 (neuronal axonal myristoylated membrane protein of 22 kDa)

2004 ◽  
Vol 379 (3) ◽  
pp. 527-532 ◽  
Author(s):  
Richard M. EPAND ◽  
Phan VUONG ◽  
Christopher M. YIP ◽  
Shohei MAEKAWA ◽  
Raquel F. EPAND
Keyword(s):  
Membrane Protein ◽  
Fluorescence Microscopy ◽  
Fluorescence Spectroscopy ◽  
Membrane Domains ◽  
Domain Formation ◽  
Membrane Domain ◽  
Terminal Fragment ◽  
N Terminus ◽  
Total Internal Reflectance ◽  
Internal Reflectance

A myristoylated peptide corresponding to the N-terminus of NAP-22 (neuronal axonal myristoylated membrane protein of 22 kDa) causes the quenching of the fluorescence of BODIPY®-TMR-labelled PtdIns(4,5)P2 in bilayers of 1-palmitoyl-2-oleoyl phosphatidylcholine containing 40 mol% cholesterol and 0.1 mol% BODIPY®–PtdIns(4,5)2. Both fluorescence spectroscopy and total internal reflectance fluorescence microscopy revealed the cholesterol-dependent nature of PtdIns(4,5)P2-enriched membrane-domain formation.

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