Site-directed modifications indicate differences in axial haem c iron ligation between the related NrfH and NapC families of multihaem c-type cytochromes

During the last decade, a number of related bacterial membrane-bound multihaem c-type cytochromes, collectively referred to as the NapC/NirT family, were identified. These proteins are generally thought to catalyse electron transport between the quinone/quinol pool and periplasmic oxidoreductases. The best-characterized members, the tetrahaem c-type cytochromes NrfH and NapC, mediate electron transport to NrfA and NapA respectively. Amino acid sequence alignments suggest that the nature and position of distal haem c iron ligands differs in NrfH and NapC proteins. Site-directed modification of potential haem c iron-ligating histidine, lysine and methionine residues in Wolinella succinogenes NrfH was performed to determine the implication in electron transport from formate to nitrite. Two histidine, one lysine and one methionine residues were found to be essential, whereas the replacement of three other conserved histidine residues, one methionine and two lysines did not prevent growth by nitrite respiration. The results contrast those previously obtained for Paracoccus pantotrophus NapC, in which four essential histidine residues have been identified that are highly likely to serve as distal haem c iron ligands. The combined experimental evidence suggests different haem ligation patterns within NapC and NrfH proteins, which might reflect their different functions in the bacterial electron transfer.

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Periplasmic nitrate reduction in Wolinella succinogenes: cytoplasmic NapF facilitates NapA maturation and requires the menaquinol dehydrogenase NapH for membrane attachment

Microbiology ◽

10.1099/mic.0.029983-0 ◽

2009 ◽

Vol 155 (8) ◽

pp. 2784-2794 ◽

Cited By ~ 26

Author(s):

Melanie Kern ◽

Jörg Simon

Keyword(s):

Electron Transport ◽

Nitrate Reductase ◽

Deletion Mutant ◽

Electron Flow ◽

Gene Clusters ◽

Nitrate Respiration ◽

Wolinella Succinogenes ◽

Periplasmic Nitrate Reductase ◽

Iron Sulfur ◽

Membrane Bound

Various nitrate-reducing bacteria produce proteins of the periplasmic nitrate reductase (Nap) system to catalyse electron transport from the membraneous quinol pool to the periplasmic nitrate reductase NapA. The composition of the corresponding nap gene clusters varies but, in addition to napA, genes encoding at least one membrane-bound quinol dehydrogenase module (NapC and/or NapGH) are regularly present. Moreover, some nap loci predict accessory proteins such as the iron–sulfur protein NapF, whose function is poorly understood. Here, the role of NapF in nitrate respiration of the Epsilonproteobacterium Wolinella succinogenes was examined. Immunoblot analysis showed that NapF is located in the membrane fraction in nitrate-grown wild-type cells whereas it was found to be a soluble cytoplasmic protein in a napH deletion mutant. This finding indicates the formation of a membrane-bound NapGHF complex that is likely to catalyse NapH-dependent menaquinol oxidation and electron transport to the iron–sulfur adaptor proteins NapG and NapF, which are located on the periplasmic and cytoplasmic side of the membrane, respectively. The cysteine residues of a CX3CP motif and of the C-terminal tetra-cysteine cluster of NapH were found to be required for interaction with NapF. A napF deletion mutant accumulated the catalytically inactive cytoplasmic NapA precursor, suggesting that electron flow or direct interaction between NapF and NapA facilitated NapA assembly and/or export. On the other hand, NapA maturation and activity was not impaired in the absence of NapH, demonstrating that soluble NapF is functional. Each of the four tetra-cysteine motifs of NapF was modified but only one motif was found to be essential for efficient NapA maturation. It is concluded that the NapGHF complex plays a multifunctional role in menaquinol oxidation, electron transfer to periplasmic NapA and maturation of the cytoplasmic NapA precursor.

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The membrane-bound tetrahaem c-type cytochrome CymA interacts directly with the soluble fumarate reductase in Shewanella

Biochemical Society Transactions ◽

10.1042/bst0300658 ◽

2002 ◽

Vol 30 (4) ◽

pp. 658-662 ◽

Cited By ~ 50

Author(s):

C. Schwalb ◽

S. K. Chapman ◽

G. A. Reid

Keyword(s):

Electron Transfer ◽

Outer Membrane ◽

Shewanella Oneidensis ◽

Anaerobic Respiration ◽

Fumarate Reductase ◽

Sulphur Compounds ◽

Sequence Alignments ◽

Membrane Bound ◽

Periplasmic Domain

Shewanella spp. demonstrate great variability in the use of terminal electron acceptors in anaerobic respiration; these include nitrate, fumarate, DMSO, trimethylamine oxide, sulphur compounds and metal oxides. These pathways open up possible applications in bioremediation. The wide variety of respiratory substrates for Shewanella is correlated with the evolution of several multi-haem membrane-bound, periplasmic and outer-membrane c-type cytochromes. The 21 kDa c-type cytochrome CymA of the freshwater strain Shewanella oneidensis MR-1 has an N-terminal membrane anchor and a globular tetrahaem periplasmic domain. According to sequence alignments, CymA is a member of the NapC/NirT family. This family of redox proteins is responsible for electron transfer from the quinone pool to periplasmic and outer-membrane-bound reductases. Prior investigations have shown that the absence of CymA results in loss of the ability to respire with Fe(III), fumarate and nitrate, indicating that CymA is involved in electron transfer to several terminal reductases. Here we describe the expression, purification and characterization of a soluble, truncated CymA (‘CymA). Potentiometric studies suggest that there are two pairs of haems with potentials of -175 and -261 mV and that ‘CymA is an efficient electron donor for the soluble fumarate reductase, flavocytochrome c3.

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Electrical characteristics of amyloid beta peptides in vertical junctions

NPG Asia Materials ◽

10.1038/s41427-021-00321-z ◽

2021 ◽

Vol 13 (1) ◽

Author(s):

Sohyeon Seo ◽

Jinju Lee ◽

Jungsue Choi ◽

G. Hwan Park ◽

Yeseul Hong ◽

...

Keyword(s):

Electron Transfer ◽

Electron Transport ◽

Amyloid Beta ◽

Field Effect Transistors ◽

Brain Diseases ◽

Electrical Characteristics ◽

Transport Pathway ◽

Sequence Dependence ◽

Aβ Oligomers ◽

Aβ Peptides

AbstractAssembled amyloid beta (Aβ) peptides have been considered pathological assemblies involved in human brain diseases, and the electron transfer or electron transport characteristics of Aβ are important for the formation of structured assemblies. Here, we report the electrical characteristics of surface-assembled Aβ peptides similar to those observed in Alzheimer’s patients. These characteristics correlate to their electron transfer characteristics. Electrical current–voltage plots of Aβ vertical junction devices show the Aβ sequence dependence of the current densities at both Aβ monomers (mono-Aβs) and Aβ oligomers (oli-Aβs), while Aβ sequence dependence is not clearly observed in the electrical characteristics of Aβ planar field effect transistors (FETs). In particular, surface oligomerization of Aβ peptides drastically decreases the activity of electron transfer, which presents a change in the electron transport pathway in the Aβ vertical junctions. Electron transport at oli-Aβ junctions is symmetric (tunneling/tunneling) due to the weak and voltage-independent coupling of the less redox-reactive oli-Aβ to the contacts, while that at mono-Aβ junctions is asymmetric (hopping/tunneling) due to redox levels of mono-Aβ voltage-dependently coupled with contact electrodes. Consequently, through vertical junctions, the sequence- and conformation-dependent electrical characteristics of Aβs can reveal their electron transfer activities.

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An electron transfer competent structural ensemble of membrane-bound cytochrome P450 1A1 and cytochrome P450 oxidoreductase

Communications Biology ◽

10.1038/s42003-020-01568-y ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Goutam Mukherjee ◽

Prajwal P. Nandekar ◽

Rebecca C. Wade

Keyword(s):

Electron Transfer ◽

Cytochrome P450 ◽

Drug Targets ◽

Catalytic Domain ◽

Cytochrome P450 1A1 ◽

P450 Oxidoreductase ◽

Distal Side ◽

Cytochrome P450 Oxidoreductase ◽

Membrane Bound ◽

Transient Interactions

AbstractCytochrome P450 (CYP) heme monooxygenases require two electrons for their catalytic cycle. For mammalian microsomal CYPs, key enzymes for xenobiotic metabolism and steroidogenesis and important drug targets and biocatalysts, the electrons are transferred by NADPH-cytochrome P450 oxidoreductase (CPR). No structure of a mammalian CYP–CPR complex has been solved experimentally, hindering understanding of the determinants of electron transfer (ET), which is often rate-limiting for CYP reactions. Here, we investigated the interactions between membrane-bound CYP 1A1, an antitumor drug target, and CPR by a multiresolution computational approach. We find that upon binding to CPR, the CYP 1A1 catalytic domain becomes less embedded in the membrane and reorients, indicating that CPR may affect ligand passage to the CYP active site. Despite the constraints imposed by membrane binding, we identify several arrangements of CPR around CYP 1A1 that are compatible with ET. In the complexes, the interactions of the CPR FMN domain with the proximal side of CYP 1A1 are supplemented by more transient interactions of the CPR NADP domain with the distal side of CYP 1A1. Computed ET rates and pathways agree well with available experimental data and suggest why the CYP–CPR ET rates are low compared to those of soluble bacterial CYPs.

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Direct electron transfer-type bioelectrocatalysis by membrane-bound aldehyde dehydrogenase from Gluconobacter oxydans and cyanide effects on its bioelectrocatalytic properties

Electrochemistry Communications ◽

10.1016/j.elecom.2020.106911 ◽

2020 ◽

pp. 106911

Author(s):

Taiki Adachi ◽

Yuki Kitazumi ◽

Osamu Shirai ◽

Kenji Kano

Keyword(s):

Electron Transfer ◽

Aldehyde Dehydrogenase ◽

Direct Electron Transfer ◽

Gluconobacter Oxydans ◽

Membrane Bound

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Ferredoxin requirement for electron transport from the carbon monoxide dehydrogenase complex to a membrane-bound hydrogenase in acetate-grown Methanosarcina thermophila.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(18)68892-1 ◽

1988 ◽

Vol 263 (9) ◽

pp. 4075-4079 ◽

Cited By ~ 3

Author(s):

K C Terlesky ◽

J G Ferry

Keyword(s):

Carbon Monoxide ◽

Electron Transport ◽

Carbon Monoxide Dehydrogenase ◽

Methanosarcina Thermophila ◽

Membrane Bound ◽

Dehydrogenase Complex

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Over-expression of an electron transport protein OmcS provides sufficient NADH for d-lactate production in cyanobacterium

Biotechnology for Biofuels ◽

10.1186/s13068-021-01956-4 ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Hengkai Meng ◽

Wei Zhang ◽

Huawei Zhu ◽

Fan Yang ◽

Yanping Zhang ◽

...

Keyword(s):

Electron Transfer ◽

Electron Transport ◽

Lactate Production ◽

Transport Protein ◽

Dominant Form ◽

Photosynthetic Production ◽

Reducing Equivalent ◽

Excess Electrons ◽

Novel Strategy ◽

Electron Transport Protein

Abstract Background An efficient supply of reducing equivalent is essential for chemicals production by engineered microbes. In phototrophic microbes, the NADPH generated from photosynthesis is the dominant form of reducing equivalent. However, most dehydrogenases prefer to utilize NADH as a cofactor. Thus, sufficient NADH supply is crucial to produce dehydrogenase-derived chemicals in cyanobacteria. Photosynthetic electron is the sole energy source and excess electrons are wasted in the light reactions of photosynthesis. Results Here we propose a novel strategy to direct the electrons to generate more ATP from light reactions to provide sufficient NADH for lactate production. To this end, we introduced an electron transport protein-encoding gene omcS into cyanobacterium Synechococcus elongatus UTEX 2973 and demonstrated that the introduced OmcS directs excess electrons from plastoquinone (PQ) to photosystem I (PSI) to stimulate cyclic electron transfer (CET). As a result, an approximately 30% increased intracellular ATP, 60% increased intracellular NADH concentrations and up to 60% increased biomass production with fourfold increased d-lactate production were achieved. Comparative transcriptome analysis showed upregulation of proteins involved in linear electron transfer (LET), CET, and downregulation of proteins involved in respiratory electron transfer (RET), giving hints to understand the increased levels of ATP and NADH. Conclusions This strategy provides a novel orthologous way to improve photosynthesis via enhancing CET and supply sufficient NADH for the photosynthetic production of chemicals.

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The direction of the proton exchange associated with the redox reactions of menaquinone during electron transport in Wolinella succinogenes

Biochimica et Biophysica Acta (BBA) - Bioenergetics ◽

10.1016/0005-2728(94)90226-7 ◽

1994 ◽

Vol 1184 (2-3) ◽

pp. 219-226 ◽

Cited By ~ 46

Author(s):

Viktor Geisler ◽

Roland Ullmann ◽

Achim Kröger

Keyword(s):

Electron Transport ◽

Redox Reactions ◽

Proton Exchange ◽

Wolinella Succinogenes

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Mutation of a single residue in the ba3 oxidase specifically impairs protonation of the pump site

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1422434112 ◽

2015 ◽

Vol 112 (11) ◽

pp. 3397-3402 ◽

Cited By ~ 16

Author(s):

Christoph von Ballmoos ◽

Nathalie Gonska ◽

Peter Lachmann ◽

Robert B. Gennis ◽

Pia Ädelroth ◽

...

Keyword(s):

Electron Transfer ◽

Time Constant ◽

Thermus Thermophilus ◽

Proton Translocation ◽

Proton Pumping ◽

Wild Type ◽

Structural Variant ◽

In The Wild ◽

Membrane Bound ◽

Proton Uptake

The ba3-type cytochrome c oxidase from Thermus thermophilus is a membrane-bound protein complex that couples electron transfer to O2 to proton translocation across the membrane. To elucidate the mechanism of the redox-driven proton pumping, we investigated the kinetics of electron and proton transfer in a structural variant of the ba3 oxidase where a putative “pump site” was modified by replacement of Asp372 by Ile. In this structural variant, proton pumping was uncoupled from internal electron transfer and O2 reduction. The results from our studies show that proton uptake to the pump site (time constant ∼65 μs in the wild-type cytochrome c oxidase) was impaired in the Asp372Ile variant. Furthermore, a reaction step that in the wild-type cytochrome c oxidase is linked to simultaneous proton uptake and release with a time constant of ∼1.2 ms was slowed to ∼8.4 ms, and in Asp372Ile was only associated with proton uptake to the catalytic site. These data identify reaction steps that are associated with protonation and deprotonation of the pump site, and point to the area around Asp372 as the location of this site in the ba3 cytochrome c oxidase.

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