scholarly journals Investigation of the Electron Transport Chain to and the Catalytic Activity of the Diheme CytochromecPeroxidase CcpA of Shewanella oneidensis

2011 ◽  
Vol 77 (17) ◽  
pp. 6172-6180 ◽  
Author(s):  
Björn Schütz ◽  
Julian Seidel ◽  
Gunnar Sturm ◽  
Oliver Einsle ◽  
Johannes Gescher
Keyword(s):  
Electron Transport ◽  
Peroxidase Activity ◽  
Electron Transport Chain ◽  
Ferric Iron ◽  
Shewanella Oneidensis ◽  
Selective Advantage ◽  
Competitive Growth ◽  
Content Type ◽  
Transport Chain

ABSTRACTBacterial dihemec-type cytochrome peroxidases (BCCPs) catalyze the periplasmic reduction of hydrogen peroxide to water. The gammaproteobacteriumShewanella oneidensisproduces the peroxidase CcpA under a number of anaerobic conditions, including dissimilatory iron-reducing conditions. We wanted to understand the function of this protein in the organism and its putative connection to the electron transport chain to ferric iron. CcpA was isolated and tested for peroxidase activity, and its structural conformation was analyzed by X-ray crystallography. CcpA exhibitedin vitroperoxidase activity and had a structure typical of diheme peroxidases. It was produced in almost equal amounts under anaerobic and microaerophilic conditions. With 50 mM ferric citrate and 50 μM oxygen in the growth medium, CcpA expression results in a strong selective advantage for the cell, which was detected in competitive growth experiments with wild-type and ΔccpAmutant cells that lack the entireccpAgene due to a markerless deletion. We were unable to reduce CcpA directly with CymA, MtrA, or FccA, which are known key players in the chain of electron transport to ferric iron and fumarate but identified the small monoheme ScyA as a mediator of electron transport between CymA and BCCP. To our knowledge, this is the first detailed description of a complete chain of electron transport to a periplasmicc-type cytochrome peroxidase. This study furthermore reports the possibility of establishing a specific electron transport chain usingc-type cytochromes.

scholarly journals Vibrio cholerae VciB Mediates Iron Reduction

2017 ◽  
Vol 199 (12) ◽  
Author(s):  
Eric D. Peng ◽  
Shelley M. Payne
Keyword(s):  
Electron Transport ◽  
Vibrio Cholerae ◽  
Ferrous Iron ◽  
Electron Transport Chain ◽  
Iron Reduction ◽  
Iron Transport ◽  
Ferric Iron ◽  
Transport Systems ◽  
Content Type ◽  
Transport Chain

ABSTRACT Vibrio cholerae is the causative agent of the severe diarrheal disease cholera. V. cholerae thrives within the human host, where it replicates to high numbers, but it also persists within the aquatic environments of ocean and brackish water. To survive within these nutritionally diverse environments, V. cholerae must encode the necessary tools to acquire the essential nutrient iron in all forms it may encounter. A prior study of systems involved in iron transport in V. cholerae revealed the existence of vciB, which, while unable to directly transport iron, stimulates the transport of iron through ferrous (Fe2+) iron transport systems. We demonstrate here a role for VciB in V. cholerae in which VciB stimulates the reduction of Fe3+ to Fe2+, which can be subsequently transported into the cell with the ferrous iron transporter Feo. Iron reduction is independent of functional iron transport but is associated with the electron transport chain. Comparative analysis of VciB orthologs suggests a similar role for other proteins in the VciB family. Our data indicate that VciB is a dimer located in the inner membrane with three transmembrane segments and a large periplasmic loop. Directed mutagenesis of the protein reveals two highly conserved histidine residues required for function. Taken together, our results support a model whereby VciB reduces ferric iron using energy from the electron transport chain. IMPORTANCE Vibrio cholerae is a prolific human pathogen and environmental organism. The acquisition of essential nutrients such as iron is critical for replication, and V. cholerae encodes a number of mechanisms to use iron from diverse environments. Here, we describe the V. cholerae protein VciB that increases the reduction of oxidized ferric iron (Fe3+) to the ferrous form (Fe2+), thus promoting iron acquisition through ferrous iron transporters. Analysis of VciB orthologs in Burkholderia and Aeromonas spp. suggest that they have a similar activity, allowing a functional assignment for this previously uncharacterized protein family. This study builds upon our understanding of proteins known to mediate iron reduction in bacteria.

scholarly journals Identification of 4-Amino-Thieno[2,3-d]Pyrimidines as QcrB Inhibitors in Mycobacterium tuberculosis

mSphere ◽  
2019 ◽  
Vol 4 (5) ◽  
Author(s):  
Gregory A. Harrison ◽  
Anne E. Mayer Bridwell ◽  
Megh Singh ◽  
Keshav Jayaraman ◽  
Leslie A. Weiss ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Electron Transport ◽  
Electron Transport Chain ◽  
Drug Target ◽  
Drug Targets ◽  
Bacterial Infections ◽  
Nonsynonymous Mutation ◽  
Content Type ◽  
Transport Chain

ABSTRACT Antibiotic resistance is a global crisis that threatens our ability to treat bacterial infections, such as tuberculosis, caused by Mycobacterium tuberculosis. Of the 10 million cases of tuberculosis in 2017, approximately 19% of new cases and 43% of previously treated cases were caused by strains of M. tuberculosis resistant to at least one frontline antibiotic. There is a clear need for new therapies that target these genetically resistant strains. Here, we report the discovery of a new series of antimycobacterial compounds, 4-amino-thieno[2,3-d]pyrimidines, that potently inhibit the growth of M. tuberculosis. To elucidate the mechanism by which these compounds inhibit M. tuberculosis, we selected for mutants resistant to a representative 4-amino-thieno[2,3-d]pyrimidine and sequenced these strains to identify the mutations that confer resistance. We isolated a total of 12 resistant mutants, each of which harbored a nonsynonymous mutation in the gene qcrB, which encodes a subunit of the electron transport chain (ETC) enzyme cytochrome bc1 oxidoreductase, leading us to hypothesize that 4-amino-thieno[2,3-d]pyrimidines target this enzyme complex. We found that addition of 4-amino-thieno[2,3-d]pyrimidines to M. tuberculosis cultures resulted in a decrease in ATP levels, supporting our model that these compounds inhibit the M. tuberculosis ETC. Furthermore, 4-amino-thieno[2,3-d]pyrimidines had enhanced activity against a mutant of M. tuberculosis deficient in cytochrome bd oxidase, which is a hallmark of cytochrome bc1 inhibitors. Therefore, 4-amino-thieno[2,3-d]pyrimidines represent a novel series of QcrB inhibitors that build on the growing number of chemical scaffolds that are able to inhibit the mycobacterial cytochrome bc1 complex. IMPORTANCE The global tuberculosis (TB) epidemic has been exacerbated by the rise in drug-resistant TB cases worldwide. To tackle this crisis, it is necessary to identify new vulnerable drug targets in Mycobacterium tuberculosis, the causative agent of TB, and develop compounds that can inhibit the bacterium through novel mechanisms of action. The QcrB subunit of the electron transport chain enzyme cytochrome bc1 has recently been validated to be a potential drug target. In the current work, we report the discovery of a new class of QcrB inhibitors, 4-amino-thieno[2,3-d]pyrimidines, that potently inhibit M. tuberculosis growth in vitro. These compounds are chemically distinct from previously reported QcrB inhibitors, and therefore, 4-amino-thieno[2,3-d]pyrimidines represent a new scaffold that can be exploited to inhibit this drug target.

scholarly journals Studies on the Mechanism by Which Anaerobiosis Prevents Swelling of Mitochondria in Vitro: Effect of Electron Transport Chain Inhibitors

1959 ◽  
Vol 234 (8) ◽  
pp. 2176-2186 ◽  
Author(s):  
F. Edmund Hunter ◽  
Jerome F. Levy ◽  
Joan Fink ◽  
Beverly Schutz ◽  
Francisco Guerra ◽  
...  
Keyword(s):  
Electron Transport ◽  
Electron Transport Chain ◽  
Transport Chain ◽  
Vitro Effect

scholarly journals Physiological Evidence for Isopotential Tunneling in the Electron Transport Chain of Methane-Producing Archaea

2017 ◽  
Vol 83 (18) ◽  
Author(s):  
Nikolas Duszenko ◽  
Nicole R. Buan
Keyword(s):  
Escherichia Coli ◽  
Electron Transport ◽  
Stationary Phase ◽  
Exponential Growth ◽  
Electron Transport Chain ◽  
Methanosarcina Barkeri ◽  
Metabolic Efficiency ◽  
Methanosarcina Acetivorans ◽  
Content Type ◽  
Transport Chain

ABSTRACT Many, but not all, organisms use quinones to conserve energy in their electron transport chains. Fermentative bacteria and methane-producing archaea (methanogens) do not produce quinones but have devised other ways to generate ATP. Methanophenazine (MPh) is a unique membrane electron carrier found in Methanosarcina species that plays the same role as quinones in the electron transport chain. To extend the analogy between quinones and MPh, we compared the MPh pool sizes between two well-studied Methanosarcina species, Methanosarcina acetivorans C2A and Methanosarcina barkeri Fusaro, to the quinone pool size in the bacterium Escherichia coli. We found the quantity of MPh per cell increases as cultures transition from exponential growth to stationary phase, and absolute quantities of MPh were 3-fold higher in M. acetivorans than in M. barkeri. The concentration of MPh suggests the cell membrane of M. acetivorans, but not of M. barkeri, is electrically quantized as if it were a single conductive metal sheet and near optimal for rate of electron transport. Similarly, stationary (but not exponentially growing) E. coli cells also have electrically quantized membranes on the basis of quinone content. Consistent with our hypothesis, we demonstrated that the exogenous addition of phenazine increases the growth rate of M. barkeri three times that of M. acetivorans. Our work suggests electron flux through MPh is naturally higher in M. acetivorans than in M. barkeri and that hydrogen cycling is less efficient at conserving energy than scalar proton translocation using MPh. IMPORTANCE Can we grow more from less? The ability to optimize and manipulate metabolic efficiency in cells is the difference between commercially viable and nonviable renewable technologies. Much can be learned from methane-producing archaea (methanogens) which evolved a successful metabolic lifestyle under extreme thermodynamic constraints. Methanogens use highly efficient electron transport systems and supramolecular complexes to optimize electron and carbon flow to control biomass synthesis and the production of methane. Worldwide, methanogens are used to generate renewable methane for heat, electricity, and transportation. Our observations suggest Methanosarcina acetivorans, but not Methanosarcina barkeri, has electrically quantized membranes. Escherichia coli, a model facultative anaerobe, has optimal electron transport at the stationary phase but not during exponential growth. This study also suggests the metabolic efficiency of bacteria and archaea can be improved using exogenously supplied lipophilic electron carriers. The enhancement of methanogen electron transport through methanophenazine has the potential to increase renewable methane production at an industrial scale.

scholarly journals In vitro effect of globotriaosylceramide on electron transport chain complexes and redox parameters

2019 ◽  
Vol 91 (2) ◽  
Author(s):  
RAFAELA M. ALVARIZ ◽  
ISABEL T.D.S. MOREIRA ◽  
GABRIELA K. CURY ◽  
CARMEN R. VARGAS ◽  
ALETHÉA G. BARSCHAK
Keyword(s):  
Electron Transport ◽  
Electron Transport Chain ◽  
Chain Complexes ◽  
Transport Chain ◽  
Vitro Effect

scholarly journals H2S-stimulated bioenergetics in chicken erythrocytes and the underlying mechanism

2020 ◽  
Vol 319 (1) ◽  
pp. R69-R78
Author(s):  
Zhuping Jin ◽  
Quanxi Zhang ◽  
Eden Wondimu ◽  
Richa Verma ◽  
Ming Fu ◽  
...  
Keyword(s):  
Electron Transport ◽  
Mammalian Cells ◽  
Electron Transport Chain ◽  
Structural Integrity ◽  
Underlying Mechanism ◽  
Atp Content ◽  
Hypoxic Conditions ◽  
Transport Chain ◽  
Chicken Erythrocytes

The production of H2S and its effect on bioenergetics in mammalian cells may be evolutionarily preserved. Erythrocytes of birds, but not those of mammals, have a nucleus and mitochondria. In the present study, we report the endogenous production of H2S in chicken erythrocytes, which was mainly catalyzed by 3-mercaptopyruvate sulfur transferase (MST). ATP content of erythrocytes was increased by MST-generated endogenous H2S under normoxic, but not hypoxic, conditions. NaHS, a H2S salt, increased ATP content under normoxic, but not hypoxic, conditions. ATP contents in the absence or presence of NaHS were eliminated by different inhibitors for mitochondrial electron transport chain in chicken erythrocytes. Succinate and glutamine, but not glucose, increased ATP content. NaHS treatment similarly increased ATP content in the presence of glucose, glutamine, or succinate, respectively. Furthermore, the expression and activity of sulfide:quinone oxidoreductase were enhanced by NaHS. The structural integrity of chicken erythrocytes was largely maintained during 2-wk NaHS treatment in vitro, whereas most of the erythrocytes without NaHS treatment were lysed. In conclusion, H2S may regulate cellular bioenergetics as well as cell survival of chicken erythrocytes, in which the functionality of the electron transport chain is involved. H2S may have different regulatory roles and mechanisms in bioenergetics of mammalian and bird cells.

scholarly journals The dynamin-related GTPase Opa1 is required for glucose-stimulated ATP production in pancreatic beta cells

2011 ◽  
Vol 22 (13) ◽  
pp. 2235-2245 ◽  
Author(s):  
Zhongyan Zhang ◽  
Nobunao Wakabayashi ◽  
Junko Wakabayashi ◽  
Yasushi Tamura ◽  
Woo-Jin Song ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Electron Transport ◽  
Beta Cells ◽  
Pancreatic Beta Cells ◽  
Electron Transport Chain ◽  
Chain Complex ◽  
Atp Production ◽  
Transport Chain

Previous studies using in vitro cell culture systems have shown the role of the dynamin-related GTPase Opa1 in apoptosis prevention and mitochondrial DNA (mtDNA) maintenance. However, it remains to be tested whether these functions of Opa1 are physiologically important in vivo in mammals. Here, using the Cre-loxP system, we deleted mouse Opa1 in pancreatic beta cells, in which glucose-stimulated ATP production in mitochondria plays a key role in insulin secretion. Beta cells lacking Opa1 maintained normal copy numbers of mtDNA; however, the amount and activity of electron transport chain complex IV were significantly decreased, leading to impaired glucose-stimulated ATP production and insulin secretion. In addition, in Opa1-null beta cells, cell proliferation was impaired, whereas apoptosis was not promoted. Consequently, mice lacking Opa1 in beta cells develop hyperglycemia. The data suggest that the function of Opa1 in the maintenance of the electron transport chain is physiologically relevant in beta cells.

scholarly journals Genomic, Proteomic, and Biochemical Analysis of the Organohalide Respiratory Pathway in Desulfitobacterium dehalogenans

2014 ◽  
Vol 197 (5) ◽  
pp. 893-904 ◽  
Author(s):  
Thomas Kruse ◽  
Bram A. van de Pas ◽  
Ariane Atteia ◽  
Klaas Krab ◽  
Wilfred R. Hagen ◽  
...  
Keyword(s):  
Electron Transport ◽  
Electron Acceptor ◽  
Electron Transport Chain ◽  
Biochemical Analysis ◽  
Active Components ◽  
Organohalide Respiration ◽  
Content Type ◽  
Membrane Complex ◽  
Redox Active ◽  
Transport Chain

Desulfitobacterium dehalogenansis able to grow by organohalide respiration using 3-chloro-4-hydroxyphenyl acetate (Cl-OHPA) as an electron acceptor. We used a combination of genome sequencing, biochemical analysis of redox active components, and shotgun proteomics to study elements of the organohalide respiratory electron transport chain. The genome ofDesulfitobacterium dehalogenansJW/IU-DC1Tconsists of a single circular chromosome of 4,321,753 bp with a GC content of 44.97%. The genome contains 4,252 genes, including six rRNA operons and six predicted reductive dehalogenases. One of the reductive dehalogenases, CprA, is encoded by a well-characterizedcprTKZEBACDgene cluster. Redox active components were identified in concentrated suspensions of cells grown on formate and Cl-OHPA or formate and fumarate, using electron paramagnetic resonance (EPR), visible spectroscopy, and high-performance liquid chromatography (HPLC) analysis of membrane extracts. In cell suspensions, these components were reduced upon addition of formate and oxidized after addition of Cl-OHPA, indicating involvement in organohalide respiration. Genome analysis revealed genes that likely encode the identified components of the electron transport chain from formate to fumarate or Cl-OHPA. Data presented here suggest that the first part of the electron transport chain from formate to fumarate or Cl-OHPA is shared. Electrons are channeled from an outward-facing formate dehydrogenase via menaquinones to a fumarate reductase located at the cytoplasmic face of the membrane. When Cl-OHPA is the terminal electron acceptor, electrons are transferred from menaquinones to outward-facing CprA, via an as-yet-unidentified membrane complex, and potentially an extracellular flavoprotein acting as an electron shuttle between the quinol dehydrogenase membrane complex and CprA.

scholarly journals Electron Transport Chain Inhibition Suppresses CD40 Expression and Sensitizes Chronic Lymphocytic Leukaemia Cells to Venetoclax

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 35-35
Author(s):  
Zhenghao Chen ◽  
Gaspard Cretenet ◽  
Valeria Carnazzo ◽  
Gerritje J. W. van der Windt ◽  
Arnon P. Kater ◽  
...  
Keyword(s):  
Electron Transport ◽  
Research Funding ◽  
Electron Transport Chain ◽  
Specific Inhibitor ◽  
Cd40 Ligation ◽  
Atp Production ◽  
Transport Chain ◽  
Cd40 Stimulation ◽  
Cd40 Expression

Alterations in expression of specifically BCL-XL and MCL-1 dictate sensitivity of CLL cells to the Bcl-2 specific inhibitor venetoclax (VEN). We and others have shown upregulation of these anti-apoptotic proteins by interaction of CLL cells with CD4+ T helper cells within their lymph node microenvironment (LN-ME) mediated by CD40 signalling. We also reported significant metabolic changes of LN-ME activated CLL cells but whether metabolic alterations can be linked to VEN resistance remains unclear. As VEN is increasingly used in early stages of CLL, better understanding and tools to circumvent VEN resistance are highly needed. We aim to reveal the metabolic adaption of CLL to CD40 signalling in connection with VEN resistance. After in vitro CD40 signalling stimulation of peripheral blood (PB) CLL cells, mitochondrial mass and glucose uptake were measured by flow cytometry, oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) were measured on Seahorse XF Analyser. The result demonstrated that CD40 stimulation enhances both oxidative phosphorylation (OXPHOS) and glycolysis. This was also confirmed by microarray and metabolomics analyses, as genes and metabolites involved in these two metabolic pathways are significantly upregulated by CD40 stimulation. To find out whether these pathways are linked to VEN resistance, PB CLL cells were treated with OXPHOS or glycolysis inhibitors during CD40 stimulation. Remarkably, OXPHOS inhibition by electron transport chain (ETC) inhibitors (rotenone, antimycin A and oligomycin) counteracted strongly for VEN resistance, while glycolysis inhibition by 2-Deoxy-D-glucose (2DG) did not. The three ETC inhibitors also attenuated CLL activation, ATP production and NAD levels. Interestingly, complex II inhibition of the ETC (TTFA and DMM) did not affect VEN resistance. Regarding BCL-2 family members induced by CD40 ligation, both MCL-1 and BCL-XL were downregulated by these ETC inhibitors. In addition, OXPHOS inhibition strongly elevates glycolysis, and vice versa, which illustrates a strong metabolic plasticity of CLL cells. To further investigate the cross-talk between CD40 signalling, VEN resistance and mitochondrial metabolism, the three main fuels of the TCA cycle were inhibited: pyruvate (by UK5099), glutamine (by DON) and fatty acids (by etomoxir). Even though the OCR and ECAR were slightly decreased by (combinations of) these fuel inhibitors, neither CD40 signalling nor VEN sensitivity was affected. Next, we inhibited PI3K by idelalisib, BTK by ibrutinib and mTOR by rapamycin, which are three downstream targets of CD40 signalling. The results showed that only rapamycin inhibited CD40 activation and metabolic activities, and none of the three inhibitors counteracts VEN resistance. Lastly, we investigated CD40 splicing and overall expression. Interestingly, CD40 stimulation has a huge impact on CD40 expression itself, and these changes were blocked by ETC inhibition. These data indicate that ETC inhibition affects CD40 signals to counteract VEN resistance, by directly affecting the expression of CD40 protein on the cell membrane. In conclusion, after CD40 stimulation, CLL cells become metabolically activated and highly flexible in the use of mitochondrial fuels. The enhanced OXPHOS but not glycolysis contributes to VEN resistance, while ETC inhibition reverses CLL VEN resistance by directly suppressing CD40 expression on CLL. These findings link CLL metabolism directly to CD40 transcription and signalling, which may contribute to clinical VEN resistance. Disclosures van der Windt: genmab: Current Employment. Kater:Abbvie: Research Funding; Roche: Research Funding; Celgene: Research Funding; Janssen: Research Funding; Genentech: Research Funding. Eldering:Genentech: Research Funding; Celgene: Research Funding; Janssen: Research Funding.

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