scholarly journals Mitochondrial Uncoupling Proteins (UCP1-UCP3) and Adenine Nucleotide Translocase (ANT1) Enhance the Protonophoric Action of 2,4-Dinitrophenol in Mitochondria and Planar Bilayer Membranes

Biomolecules ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1178
Author(s):  
Kristina Žuna ◽  
Olga Jovanović ◽  
Ljudmila Khailova ◽  
Sanja Škulj ◽  
Zlatko Brkljača ◽  
...  
Keyword(s):  
Lipid Membranes ◽  
Adenine Nucleotide ◽  
Specific Inhibitor ◽  
Membrane Conductance ◽  
Uncoupling Proteins ◽  
Site Directed Mutagenesis ◽  
Adenine Nucleotide Translocase ◽  
Planar Bilayer ◽  
Mitochondrial Uncoupling ◽  
Dynamics Simulations

2,4-Dinitrophenol (DNP) is a classic uncoupler of oxidative phosphorylation in mitochondria which is still used in “diet pills”, despite its high toxicity and lack of antidotes. DNP increases the proton current through pure lipid membranes, similar to other chemical uncouplers. However, the molecular mechanism of its action in the mitochondria is far from being understood. The sensitivity of DNP’s uncoupling action in mitochondria to carboxyatractyloside, a specific inhibitor of adenine nucleotide translocase (ANT), suggests the involvement of ANT and probably other mitochondrial proton-transporting proteins in the DNP’s protonophoric activity. To test this hypothesis, we investigated the contribution of recombinant ANT1 and the uncoupling proteins UCP1-UCP3 to DNP-mediated proton leakage using the well-defined model of planar bilayer lipid membranes. All four proteins significantly enhanced the protonophoric effect of DNP. Notably, only long-chain free fatty acids were previously shown to be co-factors of UCPs and ANT1. Using site-directed mutagenesis and molecular dynamics simulations, we showed that arginine 79 of ANT1 is crucial for the DNP-mediated increase of membrane conductance, implying that this amino acid participates in DNP binding to ANT1.

scholarly journals High membrane potential promotes alkenal-induced mitochondrial uncoupling and influences adenine nucleotide translocase conformation

2008 ◽  
Vol 413 (2) ◽  
pp. 323-332 ◽  
Author(s):  
Vian Azzu ◽  
Nadeene Parker ◽  
Martin D. Brand
Keyword(s):  
Membrane Potential ◽  
Adenine Nucleotide ◽  
Uncoupling Proteins ◽  
Adenine Nucleotide Translocase ◽  
Oxygen Species ◽  
Proton Conductance ◽  
Mitochondrial Uncoupling ◽  
Mitochondrial Inner Membrane ◽  
High Membrane Potential ◽  
Uncoupling Of Oxidative Phosphorylation

Mitochondria generate reactive oxygen species, whose downstream lipid peroxidation products, such as 4-hydroxynonenal, induce uncoupling of oxidative phosphorylation by increasing proton leak through mitochondrial inner membrane proteins such as the uncoupling proteins and adenine nucleotide translocase. Using mitochondria from rat liver, which lack uncoupling proteins, in the present study we show that energization (specifically, high membrane potential) is required for 4-hydroxynonenal to activate proton conductance mediated by adenine nucleotide translocase. Prolonging the time at high membrane potential promotes greater uncoupling. 4-Hydroxynonenal-induced uncoupling via adenine nucleotide translocase is prevented but not readily reversed by addition of carboxyatractylate, suggesting a permanent change (such as adduct formation) that renders the translocase leaky to protons. In contrast with the irreversibility of proton conductance, carboxyatractylate added after 4-hydroxynonenal still inhibits nucleotide translocation, implying that the proton conductance and nucleotide translocation pathways are different. We propose a model to relate adenine nucleotide translocase conformation to proton conductance in the presence or absence of 4-hydroxynonenal and/or carboxyatractylate.

scholarly journals Energization-dependent endogenous activation of proton conductance in skeletal muscle mitochondria

2008 ◽  
Vol 412 (1) ◽  
pp. 131-139 ◽  
Author(s):  
Nadeene Parker ◽  
Charles Affourtit ◽  
Antonio Vidal-Puig ◽  
Martin D. Brand
Keyword(s):  
Skeletal Muscle ◽  
Knockout Mice ◽  
Adenine Nucleotide ◽  
Specific Inhibitor ◽  
Adenine Nucleotide Translocase ◽  
Protonmotive Force ◽  
Proton Conductance ◽  
Wild Type ◽  
Muscle Mitochondria ◽  
Skeletal Muscle Mitochondria

Leak of protons into the mitochondrial matrix during substrate oxidation partially uncouples electron transport from phosphorylation of ADP, but the functions and source of basal and inducible proton leak in vivo remain controversial. In the present study we describe an endogenous activation of proton conductance in mitochondria isolated from rat and mouse skeletal muscle following addition of respiratory substrate. This endogenous activation increased with time, required a high membrane potential and was diminished by high concentrations of serum albumin. Inhibition of this endogenous activation by GDP [classically considered specific for UCPs (uncoupling proteins)], carboxyatractylate and bongkrekate (considered specific for the adenine nucleotide translocase) was examined in skeletal muscle mitochondria from wild-type and Ucp3-knockout mice. Proton conductance through endogenously activated UCP3 was calculated as the difference in leak between mitochondria from wild-type and Ucp3-knockout mice, and was found to be inhibited by carboxyatractylate and bongkrekate, but not GDP. Proton conductance in mitochondria from Ucp3-knockout mice was strongly inhibited by carboxyatractylate, bongkrekate and partially by GDP. We conclude the following: (i) at high protonmotive force, an endogenously generated activator stimulates proton conductance catalysed partly by UCP3 and partly by the adenine nucleotide translocase; (ii) GDP is not a specific inhibitor of UCP3, but also inhibits proton translocation by the adenine nucleotide translocase; and (iii) the inhibition of UCP3 by carboxyatractylate and bongkrekate is likely to be indirect, acting through the adenine nucleotide translocase.

scholarly journals Identification of key binding site residues of MCT1 for AR-C155858 reveals the molecular basis of its isoform selectivity

2015 ◽  
Vol 466 (1) ◽  
pp. 177-188 ◽  
Author(s):  
Bethany Nancolas ◽  
Richard B. Sessions ◽  
Andrew P. Halestrap
Keyword(s):  
Molecular Dynamics ◽  
Amino Acids ◽  
Binding Site ◽  
Molecular Basis ◽  
Specific Inhibitor ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Isoform Specificity ◽  
Isoform Selectivity ◽  
Dynamics Simulations

A combination of molecular modelling, site-directed mutagenesis and molecular dynamics simulations define the binding site of MCT1 for AR-C155858, a potent and specific inhibitor. Key amino acids within the binding site differ between MCT1 and MCT4 accounting for isoform specificity.

scholarly journals A comparative study of the inhibitory effects of purine nucleotides and carboxyatractylate on the uncoupling protein-3 and adenine nucleotide translocase.

2010 ◽  
Vol 57 (4) ◽  
Author(s):  
Natalia P Komelina ◽  
Zarif G Amerkhanov
Keyword(s):  
Fatty Acid ◽  
Adenine Nucleotide ◽  
Uncoupling Protein ◽  
Specific Inhibitor ◽  
Inhibitory Effect ◽  
Ground Squirrels ◽  
Adenine Nucleotide Translocase ◽  
Purine Nucleotides ◽  
Chloride Permeability ◽  
Brown Adipose

Uncoupling proteins (UCPs) mediate fatty acid-induced proton cycling in mitochondria, which is stimulated by superoxide and inhibited by GDP. Fatty acid anions can also be transported by adenine nucleotide translocase (ANT), thus resulting in the uncoupling of oxidative phosphorylation. In the present work, an attempt was made to distinguish between the protonophoric activity of UCP3 and that of ANT using inhibition analysis. This study was carried out using mitochondria from skeletal muscles of hibernating Yakut ground squirrel, which have a significant level of UCP3 mRNA. We found that millimolar concentrations of GDP, which is considered to be a specific inhibitor of UCPs, slightly recoupled the mitochondrial respiration and restored the membrane potential. Addition of the specific ANT inhibitor CAT (carboxyatractylate), in micromolar concentration, prior to GDP prevented its recoupling effect. Moreover, GDP and ADP exhibited a competitive kinetic behavior with respect to ANT. In brown adipose tissue, CAT did not prevent the UCP1-iduced increase in chloride permeability and the inhibitory effect of GDP, thus confirming the inability of CAT to affect UCP1. These results allow us to conclude that the recoupling effect of purine nucleotides on skeletal muscle mitochondria of hibernating ground squirrels can be explained by interaction of the nucleotides with ANT, whereas UCP3 is not involved in the process.

scholarly journals A Fluorescence-Based Method to Measure ADP/ATP Exchange of Recombinant Adenine Nucleotide Translocase in Liposomes

Biomolecules ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 685
Author(s):  
Jürgen Kreiter ◽  
Eric Beitz ◽  
Elena E. Pohl
Keyword(s):  
Exchange Rates ◽  
Adenine Nucleotide ◽  
Membrane Conductance ◽  
Adenine Nucleotide Translocase ◽  
Mitochondrial Proteins ◽  
Binding Affinities ◽  
Substrate Transport ◽  
Bongkrekic Acid ◽  
Aspartate Glutamate Carrier ◽  
Specific Inhibitors

Several mitochondrial proteins, such as adenine nucleotide translocase (ANT), aspartate/glutamate carrier, dicarboxylate carrier, and uncoupling proteins 2 and 3, are suggested to have dual transport functions. While the transport of charge (protons and anions) is characterized by an alteration in membrane conductance, investigating substrate transport is challenging. Currently, mainly radioactively labeled substrates are used, which are very expensive and require stringent precautions during their preparation and use. We present and evaluate a fluorescence-based method using Magnesium Green (MgGrTM), a Mg2+-sensitive dye suitable for measurement in liposomes. Given the different binding affinities of Mg2+ for ATP and ADP, changes in their concentrations can be detected. We obtained an ADP/ATP exchange rate of 3.49 ± 0.41 mmol/min/g of recombinant ANT1 reconstituted into unilamellar liposomes, which is comparable to values measured in mitochondria and proteoliposomes using a radioactivity assay. ADP/ATP exchange calculated from MgGrTM fluorescence solely depends on the ANT1 content in liposomes and is inhibited by the ANT-specific inhibitors, bongkrekic acid and carboxyatractyloside. The application of MgGrTM to investigate ADP/ATP exchange rates contributes to our understanding of ANT function in mitochondria and paves the way for the design of other substrate transport assays.

Molecular Basis of Glucose Transport Mechanism in Plants

2019 ◽  
Author(s):  
Balaji Selvam ◽  
Ya-Chi Yu ◽  
Liqing Chen ◽  
Diwakar Shukla
Keyword(s):  
Molecular Dynamics ◽  
Free Energy ◽  
Molecular Dynamics Simulations ◽  
Conformational Changes ◽  
Transport Mechanism ◽  
Conformational Dynamics ◽  
Site Directed Mutagenesis ◽  
Free Energy Barrier ◽  
Transport Cycle ◽  
Dynamics Simulations

<p>The SWEET family belongs to a class of transporters in plants that undergoes large conformational changes to facilitate transport of sugar molecules across the cell membrane. However, the structures of their functionally relevant conformational states in the transport cycle have not been reported. In this study, we have characterized the conformational dynamics and complete transport cycle of glucose in OsSWEET2b transporter using extensive molecular dynamics simulations. Using Markov state models, we estimated the free energy barrier associated with different states as well as 1 for the glucose the transport mechanism. SWEETs undergoes structural transition to outward-facing (OF), Occluded (OC) and inward-facing (IF) and strongly support alternate access transport mechanism. The glucose diffuses freely from outside to inside the cell without causing major conformational changes which means that the conformations of glucose unbound and bound snapshots are exactly same for OF, OC and IF states. We identified a network of hydrophobic core residues at the center of the transporter that restricts the glucose entry to the cytoplasmic side and act as an intracellular hydrophobic gate. The mechanistic predictions from molecular dynamics simulations are validated using site-directed mutagenesis experiments. Our simulation also revealed hourglass like intermediate states making the pore radius narrower at the center. This work provides new fundamental insights into how substrate-transporter interactions actively change the free energy landscape of the transport cycle to facilitate enhanced transport activity.</p>

scholarly journals New insights into structure and function of bis-phosphinic acid derivatives and implications for CFTR modulation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sara Bitam ◽  
Ahmad Elbahnsi ◽  
Geordie Creste ◽  
Iwona Pranke ◽  
Benoit Chevalier ◽  
...  
Keyword(s):  
Phosphinic Acid ◽  
Site Directed Mutagenesis ◽  
Side Chain ◽  
Transmembrane Conductance Regulator ◽  
Intracellular Loop ◽  
Respiratory Cells ◽  
Cftr Protein ◽  
Dynamics Simulations ◽  
And Function ◽  
Molecular Mode

AbstractC407 is a compound that corrects the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) protein carrying the p.Phe508del (F508del) mutation. We investigated the corrector effect of c407 and its derivatives on F508del-CFTR protein. Molecular docking and dynamics simulations combined with site-directed mutagenesis suggested that c407 stabilizes the F508del-Nucleotide Binding Domain 1 (NBD1) during the co-translational folding process by occupying the position of the p.Phe1068 side chain located at the fourth intracellular loop (ICL4). After CFTR domains assembly, c407 occupies the position of the missing p.Phe508 side chain. C407 alone or in combination with the F508del-CFTR corrector VX-809, increased CFTR activity in cell lines but not in primary respiratory cells carrying the F508del mutation. A structure-based approach resulted in the synthesis of an extended c407 analog G1, designed to improve the interaction with ICL4. G1 significantly increased CFTR activity and response to VX-809 in primary nasal cells of F508del homozygous patients. Our data demonstrate that in-silico optimized c407 derivative G1 acts by a mechanism different from the reference VX-809 corrector and provide insights into its possible molecular mode of action. These results pave the way for novel strategies aiming to optimize the flawed ICL4–NBD1 interface.

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