scholarly journals Uncouplers can shuttle between localized energy-coupling sites during photophosphorylation by chromatophores of Rhodopseudomonas capsulata N22

1983 ◽  
Vol 212 (1) ◽  
pp. 25-30 ◽  
Author(s):  
G D Hitchens ◽  
D B Kell
Keyword(s):  
Electron Transport ◽  
Atp Synthase ◽  
Electron Flow ◽  
Energy Coupling ◽  
Turnover Time ◽  
Rhodopseudomonas Capsulata ◽  
Antimycin A ◽  
Set Up ◽  
Synthase Inhibitor ◽  
Chromatophore Membrane

Two models of the action of uncoupler molecules in inhibiting photophosphorylation in bacterial chromatophores are considered: either uncoupler molecules shuttle rapidly between energy-coupling sites, or uncoupler molecules that are bound to particular sites in the chromatophores for a time that is comparable with the turnover time of the photophosphorylation apparatus may uncouple by a co-operative ‘substoichiometric’ mechanism. It is found that the titre of uncoupler necessary to cause complete uncoupling is lowered if the rate of photophosphorylation is initially decreased by partially restricting electron flow with an appropriate titre of antimycin A. This result indicates that uncoupler molecules shuttle rapidly between energy coupling in which the energized intermediate between electron transport and phosphorylation is delocalized over the entire chromatophore membrane and those in which it is not. If the rate of photophosphorylation is partially restricted with the covalent H+-translocating ATP synthase inhibitor dicyclohexylcarbodi-imide, the titre of uncoupler necessary to effect complete inhibition of photophosphorylation is also decreased relative to that in which the covalent H+-ATP synthase inhibitor is absent. This important result appears to be inconsistent with models of electron-transport phosphorylation in which the ‘energized state’ of the chromatophore membrane that is set up by electron transport and utilized in photophosphorylation is delocalized over the entire chromatophore membrane.

Localized energy coupling during photophosphorylation by chromatophores of Rhodopseudomonas capsulata N22

1982 ◽  
Vol 2 (10) ◽  
pp. 743-749 ◽  
Author(s):  
G. Duncan Hitchens ◽  
Douglas B. Kell
Keyword(s):  
Free Energy ◽  
Electron Transport ◽  
Atp Synthase ◽  
Electron Transport Chain ◽  
Energy Coupling ◽  
Rhodopseudomonas Capsulata ◽  
Titration Method ◽  
Dual Inhibitor ◽  
Transport Chain ◽  
Synthase Inhibitor

The principle of the dual inhibitor titration method for testing models of electron-transport phosphorylation is outlined, and the method is applied to the study of photophosphorylation in bacterial chromatophores. It is concluded that energy coupling is strictly localized in nature in this system, in the sense that free energy released by a particular electron-transport chain may be used only by a particular H+-ATP synthase. Dual inhibitor titrations using the uncoupler SF 6847 and the H+-ATP synthase inhibitor oligomycin indicate that uncouplers act by shuttling rapidly between the localized energy-coupling sites.

scholarly journals TBAJ-876 Displays Bedaquiline-Like Mycobactericidal Potency without Retaining the Parental Drug’s Uncoupler Activity

2019 ◽  
Vol 64 (2) ◽  
Author(s):  
Jickky Palmae Sarathy ◽  
Priya Ragunathan ◽  
Christopher B. Cooper ◽  
Anna M. Upton ◽  
Gerhard Grüber ◽  
...  
Keyword(s):  
Electron Transport ◽  
Atp Synthase ◽  
Mechanism Of Action ◽  
Bactericidal Activity ◽  
Atp Synthesis ◽  
Synthase Inhibitor ◽  
Time Kill

ABSTRACT The diarylquinoline F1FO-ATP synthase inhibitor bedaquiline (BDQ) displays protonophore activity. Thus, uncoupling electron transport from ATP synthesis appears to be a second mechanism of action of this antimycobacterial drug. Here, we show that the new BDQ analogue TBAJ-876 did not retain the parental drug’s protonophore activity. Comparative time-kill analyses revealed that both compounds exert the same bactericidal activity. These results suggest that the uncoupler activity is not required for the bactericidal activity of diarylquinolines.

scholarly journals Energy Conservation by the H2:Heterodisulfide Oxidoreductase from Methanosarcina mazei Gö1: Identification of Two Proton-Translocating Segments

1999 ◽  
Vol 181 (13) ◽  
pp. 4076-4080 ◽  
Author(s):  
Tina Ide ◽  
Sebastian Bäumer ◽  
Uwe Deppenmeier
Keyword(s):  
Electron Transport ◽  
Atp Synthase ◽  
Cytoplasmic Membrane ◽  
Respiratory Control ◽  
Atp Synthesis ◽  
Heterodisulfide Reductase ◽  
Methanosarcina Mazei ◽  
Energy Conserving ◽  
Membrane Bound ◽  
Synthase Inhibitor

ABSTRACT The membrane-bound H2:heterodisulfide oxidoreductase system of the methanogenic archaeon Methanosarcina mazeiGö1 catalyzed the H2-dependent reduction of 2-hydroxyphenazine and the dihydro-2-hydroxyphenazine-dependent reduction of the heterodisulfide of HS-CoM and HS-CoB (CoM-S-S-CoB). Washed inverted vesicles of this organism were found to couple both processes with the transfer of protons across the cytoplasmic membrane. The maximal H+/2e− ratio was 0.9 for each reaction. The electrochemical proton gradient (ΔμH+ ) thereby generated was shown to drive ATP synthesis from ADP plus Pi, exhibiting stoichiometries of 0.25 ATP synthesized per two electrons transported for both partial reactions. ATP synthesis and the generation of ΔμH+ were abolished by the uncoupler 3,5-di-tert-butyl-4-hydroxybenzylidenemalononitrile (SF 6847). The ATP synthase inhibitorN,N′-dicyclohexylcarbodiimide did not affect H+ translocation but led to an almost complete inhibition of ATP synthesis and decreased the electron transport rates. The latter effect was relieved by the addition of SF 6847. Thus, the energy-conserving systems showed a stringent coupling which resembles the phenomenon of respiratory control. The results indicate that two different proton-translocating segments are present in the H2:heterodisulfide oxidoreductase system; the first involves the 2-hydroxyphenazine-dependent hydrogenase, and the second involves the heterodisulfide reductase.

scholarly journals On the extent of localization of the energized membrane state in chromatophores from Rhodopseudomonas capsulata N22

1982 ◽  
Vol 206 (2) ◽  
pp. 351-357 ◽  
Author(s):  
G D Hitchens ◽  
D B Kell
Keyword(s):  
Electron Transport ◽  
Atp Synthase ◽  
Electron Transport Chain ◽  
Relative Number ◽  
Coupling Model ◽  
Rhodopseudomonas Capsulata ◽  
Apparent Paradox ◽  
Model Free ◽  
Transport Chain ◽  
Chemiosmotic Coupling

1. The principle of the double-inhibitor titration method for assessing competing models of electron transport phosphorylation is expounded. 2. This principle is applied to photophosphorylation by chromatophores from Rhodopseudomonas capsulata N22. 3. It is found that, in contrast to the predictions of the chemiosmotic coupling model, free energy transfer is confined to individual electron transport chain and ATP synthase complexes. 4. This conclusion is not weakened by arguments concerning, the degree of uncoupling in the native chromatophore preparation or the relative number of electron transport chain and ATP synthase complexes present. 5. Photophosphorylation is completely inhibited by the uncoupler SF 6847 at a concentration corresponding to 0.31 molecules per electron transport chain. 6. The apparent paradox is solved by the proposal, consistent with the available evidence on the mode of action of uncouplers, that uncoupler binding causes a co-operative conformation transition in the chromatophore membrane, which leads to uncoupling and which is not present in the absence of uncoupler.

Interaction of Photosystem II Herbicides with Bicarbonate and Formate in Their Effects on Photosynthetic Electron Flow

1984 ◽  
Vol 39 (5) ◽  
pp. 374-377 ◽  
Author(s):  
J. J. S. van Rensen
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Hill Reaction ◽  
Amaranthus Hybridus ◽  
Apparent Affinity ◽  
Photosynthetic Electron Flow ◽  
Different Characteristics ◽  
The Hill

The reactivation of the Hill reaction in CO2-depleted broken chloroplasts by various concentrations of bicarbonate was measured in the absence and in the presence of photosystem II herbicides. It appears that these herbicides decrease the apparent affinity of the thylakoid membrane for bicarbonate. Different characteristics of bicarbonate binding were observed in chloroplasts of triazine-resistant Amaranthus hybridus compared to the triazine-sensitive biotype. It is concluded that photosystem II herbicides, bicarbonate and formate interact with each other in their binding to the Qв-protein and their interference with photosynthetic electron transport.

scholarly journals Genome-Wide Screening Identifies Six Genes That Are Associated with Susceptibility to Escherichia coli Microcin PDI

2015 ◽  
Vol 81 (20) ◽  
pp. 6953-6963 ◽  
Author(s):  
Zhe Zhao ◽  
Lauren J. Eberhart ◽  
Lisa H. Orfe ◽  
Shao-Yeh Lu ◽  
Thomas E. Besser ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Atp Synthase ◽  
Disulfide Bonds ◽  
Gene Knockout ◽  
Single Gene ◽  
Site Directed Mutagenesis ◽  
Content Type ◽  
E Coli ◽  
Synthase Inhibitor ◽  
Loss Of Susceptibility

ABSTRACTThe microcin PDI inhibits a diverse group of pathogenicEscherichia colistrains. Coculture of a single-gene knockout library (BW25113;n= 3,985 mutants) against a microcin PDI-producing strain (E. coli25) identified six mutants that were not susceptible (ΔatpA, ΔatpF, ΔdsbA, ΔdsbB, ΔompF, and ΔompR). Complementation of these genes restored susceptibility in all cases, and the loss of susceptibility was confirmed through independent gene knockouts inE. coliO157:H7 Sakai. Heterologous expression ofE. coliompFconferred susceptibility toSalmonella entericaandYersinia enterocoliticastrains that are normally unaffected by microcin PDI. The expression of chimeric OmpF and site-directed mutagenesis revealed that the K47G48N49region within the first extracellular loop ofE. coliOmpF is a putative binding site for microcin PDI. OmpR is a transcriptional regulator forompF, and consequently loss of susceptibility by the ΔompRstrain most likely is related to this function. Deletion of AtpA and AtpF, as well as AtpE and AtpH (missed in the original library screen), resulted in the loss of susceptibility to microcin PDI and the loss of ATP synthase function. Coculture of a susceptible strain in the presence of an ATP synthase inhibitor resulted in a loss of susceptibility, confirming that a functional ATP synthase complex is required for microcin PDI activity. Intransexpression ofompFin the ΔdsbAand ΔdsbBstrains did not restore a susceptible phenotype, indicating that these proteins are probably involved with the formation of disulfide bonds for OmpF or microcin PDI.

Dual Mutations Reveal Interactions Between Components of Oxidative Phosphorylation in Kluyveromyces lactis

Genetics ◽  
2001 ◽  
Vol 159 (3) ◽  
pp. 929-938
Author(s):  
G D Clark-Walker ◽  
X J Chen
Keyword(s):  
Electron Transport ◽  
Oxidative Phosphorylation ◽  
Atp Synthase ◽  
Kluyveromyces Lactis ◽  
Mitochondrial Protein ◽  
Proton Pumping ◽  
Nuclear Genes ◽  
Suppressor Activity ◽  
Inner Membrane ◽  
Atp Production

Abstract Loss of mtDNA or mitochondrial protein synthesis cannot be tolerated by wild-type Kluyveromyces lactis. The mitochondrial function responsible for ρ0-lethality has been identified by disruption of nuclear genes encoding electron transport and F0-ATP synthase components of oxidative phosphorylation. Sporulation of diploid strains heterozygous for disruptions in genes for the two components of oxidative phosphorylation results in the formation of nonviable spores inferred to contain both disruptions. Lethality of spores is thought to result from absence of a transmembrane potential, ΔΨ, across the mitochondrial inner membrane due to lack of proton pumping by the electron transport chain or reversal of F1F0-ATP synthase. Synergistic lethality, caused by disruption of nuclear genes, or ρ0-lethality can be suppressed by the atp2.1 mutation in the β-subunit of F1-ATPase. Suppression is viewed as occurring by an increased hydrolysis of ATP by mutant F1, allowing sufficient electrogenic exchange by the translocase of ADP in the matrix for ATP in the cytosol to maintain ΔΨ. In addition, lethality of haploid strains with a disruption of AAC encoding the ADP/ATP translocase can be suppressed by atp2.1. In this case suppression is considered to occur by mutant F1 acting in the forward direction to partially uncouple ATP production, thereby stimulating respiration and relieving detrimental hyperpolarization of the inner membrane. Participation of the ADP/ATP translocase in suppression of ρ0-lethality is supported by the observation that disruption of AAC abolishes suppressor activity of atp2.1.

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