scholarly journals The interaction of methanol dehydrogenase and its cytochrome electron acceptor

1995 ◽  
Vol 312 (1) ◽  
pp. 261-265 ◽  
Author(s):  
S L Dales ◽  
C Anthony
Keyword(s):  
Electron Transfer ◽  
Electron Acceptor ◽  
Methanol Dehydrogenase ◽  
Ionic Interactions ◽  
Optimal Position ◽  
Factors Affecting ◽  
Carboxylate Groups ◽  
Initial Interaction ◽  
Cytochrome Cl ◽  
Initial Binding

A fluorescence method is described for direct measurement of the interaction between methanol dehydrogenase (MDH) and its electron acceptor cytochrome cL. This has permitted a distinction to be made between factors affecting electron transfer and those affecting the initial binding or docking process. It was confirmed that the initial interaction is electrostatic, but previous conclusions with respect to the mechanism of EDTA inhibition have been modified. It is proposed that the initial ‘docking’ of MDH and cytochrome cL is by way of ionic interactions between lysyl residues on its surface and carboxylate groups on the surface of cytochrome cL. This interaction is not inhibited by EDTA, which we suggest acts by binding to nearby lysyl residues, thus preventing movement of the ‘docked’ cytochrome to its optimal position for electron transfer, which probably involves interaction with the hydrophobic funnel in the surface of MDH.

scholarly journals The interaction of methanol dehydrogenase and cytochrome cL in the acidophilic methylotroph Acetobacter methanolicus

1991 ◽  
Vol 280 (1) ◽  
pp. 139-146 ◽  
Author(s):  
H T C Chan ◽  
C Anthony
Keyword(s):  
Electrostatic Interactions ◽  
High Ionic Strength ◽  
Methanol Dehydrogenase ◽  
Beta Subunit ◽  
Ionic Interactions ◽  
Oxidoreductase Activity ◽  
Strength Of Interaction ◽  
Lysine Residues ◽  
Arginine Residues ◽  
Cytochrome Cl

The quinoprotein methanol dehydrogenase (MDH) of Acetobacter methanolicus has an alpha 2 beta 2 structure. By contrast with other MDHs, the beta-subunit (approx. 8.5 kDa) does not contain the five lysine residues previously proposed to be involved in ionic interactions with the electron acceptor cytochrome cL. That electrostatic interactions are involved was confirmed by the demonstration that methanol:cytochrome cL oxidoreductase activity was inhibited by high ionic strength (I), the strength of interaction being inversely related to the square root of I. Specific modifiers of arginine residues on MDH inhibited this reaction but not the dye-linked MDH activity. Modification of lysine residues on MDH that altered its charge had no effect on the dye-linked activity but inhibited reaction with cytochrome cL. When the charge was retained on modification of lysine residues, little effect on either activity was observed. Cross-linking experiments confirmed that lysine residues on the alpha-subunit, but not the beta-subunit, are involved in the ‘docking’ process between the proteins.

scholarly journals Studies on electron transfer from methanol dehydrogenase to cytochrome cL, both purified from Hyphomicrobium X

1989 ◽  
Vol 257 (1) ◽  
pp. 87-94 ◽  
Author(s):  
M Dijkstra ◽  
J Frank ◽  
J A Duine
Keyword(s):  
Electron Transfer ◽  
Electron Acceptor ◽  
Substrate Oxidation ◽  
Methanol Dehydrogenase ◽  
Methylotrophic Bacteria ◽  
Ph Optimum ◽  
Oxidation Step ◽  
Reaction Cycles ◽  
Rate Limiting

Ferricytochrome cL isolated from Hyphomicrobium X is an electron acceptor in assays for homologous methanol dehydrogenase (MDH), albeit a poor one compared with artificial dyes. The intermediates of MDH seen during the reaction are identical with those observed with Wurster's Blue as electron acceptor, indicating that the reaction cycles are similar. The assay showed a pH optimum of approx. 7.0 and scarcely any stimulation by NH4Cl, this being in contrast with assays with artificial dyes, where strong activation by NH4Cl and much higher pH optima have been reported. From the results obtained with stopped-flow as well as steady-state kinetics, combined with the isotope effects found for C2H3OH, it appeared that the dissimilarities between the electron acceptors can be explained from different rate-limiting steps in the reaction cycles. Ferricytochrome cL is an excellent oxidant of the reduced MDH forms at pH 7.0, but the substrate oxidation step is very slow and the activation by NH4Cl is very poor at this pH. At pH 9.0 the reverse situation exists: ferricytochrome cL is a poor oxidant of the reduced forms of MDH at this pH. No C2H3OH isotope effect was observed under these conditions, indicating that substrate oxidation is not rate-limiting, so that activation by NH4Cl cannot be found. Since just the opposite holds for assays with artificial dyes, the poor electron-acceptor capability and the different pH optimum of ferricytochrome cL as well as the insignificant activating effect of NH4Cl (all compared with artificial assays) can be explained. Although different views have been reported on the rate-limiting steps in the systems from Methylophilus methylotrophus and Methylobacterium sp. strain AM1, these are most probably incorrect, as rate-limiting electron transfer between ferrocytochrome cL and horse heart ferricytochrome c can occur. Therefore the conclusions derived for the Hyphomicrobium X system might also apply to the systems from other methylotrophic bacteria. Comparison of the assays performed in vitro (at pH 7.0) having ferricytochrome cL and Wurster's Blue as electron acceptor with methanol oxidation by whole cells shows that the former has similarity whereas the latter has not, this being although ferricytochrome cL is a poor electron acceptor in the assay performed in vitro. The reason for this is the absence of a (natural) activator able to activate the (rate-limiting) substrate oxidation step at physiological pH values.

scholarly journals The soluble cytochromes c of methanol-grown Hyphomicrobium X. Evidence against the involvement of autoreduction in electron-acceptor functioning of cytochrome cL

1988 ◽  
Vol 251 (2) ◽  
pp. 467-474 ◽  
Author(s):  
M Dijkstra ◽  
J Frank ◽  
J E van Wielink ◽  
J A Duine
Keyword(s):  
Electron Acceptor ◽  
Protein Molecule ◽  
Methanol Dehydrogenase ◽  
Methylotrophic Bacteria ◽  
High Ph ◽  
Native Proteins ◽  
Cytochromes C ◽  
Reverse Situation ◽  
Cytochrome Cl ◽  
Reduced Forms

Hyphomicrobium X, grown on methanol with O2 or nitrate as electron acceptor, contains two major soluble cytochromes c. These were isolated in electrophoretically homogeneous form. They are related to cytochromes c already described for other methylotrophic bacteria and designated cytochromes cH and cL (properties indicated in that order) in view of the following characteristics: absorption maxima of the reduced forms (414, 520 and 551 nm and 414, 520 and 550 nm); molar absorption coefficients of the alpha-bands (23,700 M-1.cm-1 and 21,600 M-1.cm-1); maxima of the alpha-bands (no splitting) at 77 K (547.6 nm and 548.5 nm); Mr values of the native proteins (15,000 and 19,500); pI values (7.4 and 7.5, and 4.3); midpoint potentials at pH 7.0 (+292 mV and +270 mV). Both were monomers containing 1 haem c group per protein molecule, the oxidized forms binding cyanide at high pH. Autoreduction also occurred at high pH but at a rate significantly lower than that reported for other ferricytochromes c. On the other hand, the reverse situation applies to the reduction of ferricytochrome cL by reduced methanol dehydrogenase, the reduction occurring instantaneously at pH 7 but much more slowly at pH 9 (ferricytochrome cH was reduced at a 7-fold lower rate, but the rates at pH 7 and 9 were similar). Insignificant reduction was observed with cyclopropanol-inactivated enzyme or with enzyme in the presence of EDTA. In view of the dissimilarities, it is concluded that different mechanisms operate in the autoreduction of ferricytochrome cL and in its reduction by reduced methanol dehydrogenase.

scholarly journals Molecular Engineering for High-Performance Fullerene Broadband Photodetector

2021 ◽  
Author(s):  
Mingming Su ◽  
Yajing Hu ◽  
Ao Yu ◽  
Zhiyao Peng ◽  
Wangtao Long ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Low Temperature ◽  
Electron Acceptor ◽  
Photoinduced Electron Transfer ◽  
High Performance ◽  
Organic Molecules ◽  
Low Cost ◽  
Molecular Engineering ◽  
Temperature Requirement ◽  
High Flexibility

Broadband photodetectors fabricated with organic molecules have the advantages of low cost, high flexibility, easy processing and low-temperature requirement. Fullerene molecules, due to the electron acceptor and photoinduced electron transfer...

Selective chemochromic and chemically-induced photochromic response of a metal–organic framework

2020 ◽  
Vol 56 (44) ◽  
pp. 5929-5932 ◽  
Author(s):  
Peng Li ◽  
Qi Sui ◽  
Meng-Yue Guo ◽  
Shuai-Liang Yang ◽  
Ran Bu ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electron Acceptor ◽  
Photoinduced Electron Transfer ◽  
Color Change ◽  
Metal Organic Framework ◽  
Confined Space ◽  
Chemically Induced ◽  
Metal Organic ◽  
Organic Framework

The MOF provides unique confined space furnished with electron acceptor sites, and exposure to amines/alcohols causes specific and size-selective direct/UV-assisted color change owing to spontaneous/photoinduced electron transfer.

Quantification of Electron Transfer Rates to a Solid Phase Electron Acceptor through the Stages of Biofilm Formation from Single Cells to Multicellular Communities

2010 ◽  
Vol 44 (7) ◽  
pp. 2721-2727 ◽  
Author(s):  
Jeffrey S. McLean ◽  
Greg Wanger ◽  
Yuri A. Gorby ◽  
Martin Wainstein ◽  
Jeff McQuaid ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electron Acceptor ◽  
Biofilm Formation ◽  
Solid Phase ◽  
Single Cells ◽  
Transfer Rates

scholarly journals Identification of different putative outer membrane electron conduits necessary for Fe(III) citrate, Fe(III) oxide, Mn(IV) oxide, or electrode reduction by Geobacter sulfurreducens

2017 ◽  
Author(s):  
Fernanda Jiménez Otero ◽  
Chi Ho Chan ◽  
Daniel R. Bond
Keyword(s):  
Electron Transfer ◽  
Outer Membrane ◽  
Electron Acceptor ◽  
Single Gene ◽  
Gene Clusters ◽  
Geobacter Sulfurreducens ◽  
Transcriptional Analysis ◽  
Growth Defect ◽  
Redox Potentials ◽  
Wild Type

AbstractAt least five gene clusters in the Geobacter sulfurreducens genome encode putative ‘electron conduits’ implicated in electron transfer across the outer membrane, each containing a periplasmic multiheme c-type cytochrome, integral outer membrane anchor, and outer membrane redox lipoprotein(s). Markerless single gene cluster deletions and all possible multiple deletion combinations were constructed and grown with soluble Fe(III) citrate, Fe(III)- and Mn(IV)-oxides, and graphite electrodes poised at +0.24 V and −0.1 V vs. SHE. Different gene clusters were necessary for reduction of each electron acceptor. During metal oxide reduction, deletion of the previously described omcBC cluster caused defects, but deletion of additional components in an ΔomcBC background, such as extEFG, were needed to produce defects greater than 50% compared to wild type. Deletion of all five gene clusters abolished all metal reduction. During electrode reduction, only the ΔextABCD mutant had a severe growth defect at both redox potentials, while this mutation did not affect Fe(III)-oxide, Mn(IV)-oxide, or Fe(III) citrate reduction. Some mutants containing only one cluster were able to reduce particular terminal electron acceptors better than wild type, suggesting routes for improvement by targeting specific electron transfer pathways. Transcriptomic comparisons between fumarate and electrode-based growth showed all of these ext clusters to be constitutive, and transcriptional analysis of the triple-deletion strain containing only extABCD detected no significant changes in expression of known redox proteins or pili components. These genetic experiments reveal new outer membrane conduit complexes necessary for growth of G. sulfurreducens, depending on the available extracellular electron acceptor.

scholarly journals Identification of different putative outer membrane electron conduits necessary for Fe(III) citrate, Fe(III)-oxide, Mn(IV)-oxide, or electrode reduction by Geobacter sulfurreducens .

2018 ◽  
Author(s):  
Fernanda Jiménez Otero ◽  
Chi Ho Chan ◽  
Daniel R Bond
Keyword(s):  
Electron Transfer ◽  
Outer Membrane ◽  
Electron Acceptor ◽  
Single Gene ◽  
Gene Clusters ◽  
Geobacter Sulfurreducens ◽  
Transcriptional Analysis ◽  
Growth Defect ◽  
Redox Potentials ◽  
Wild Type

At least five gene clusters in the Geobacter sulfurreducens genome encode putative ‘electron conduits’ implicated in electron transfer across the outer membrane, each containing a periplasmic multiheme c -type cytochrome, integral outer membrane anchor, and outer membrane redox lipoprotein(s). Markerless single gene cluster deletions and all possible multiple deletion combinations were constructed and grown with soluble Fe(III) citrate, Fe(III)- and Mn(IV)-oxides, and graphite electrodes poised at +0.24 V and -0.1 V vs. SHE. Different gene clusters were necessary for reduction of each electron acceptor. During metal oxide reduction, deletion of the previously described omcBC cluster caused defects, but deletion of additional components in an Δ omcBC background, such as extEFG , were needed to produce defects greater than 50% compared to wild type. Deletion of all five gene clusters abolished all metal reduction. During electrode reduction, only the Δ extABCD mutant had a severe growth defect at both redox potentials, while this mutation did not affect Fe(III)-oxide, Mn(IV)-oxide, or Fe(III) citrate reduction. Some mutants containing only one cluster were able to reduce particular terminal electron acceptors better than wild type, suggesting routes for improvement by targeting specific electron transfer pathways. Transcriptomic comparisons between fumarate and electrode-based growth showed all of these ext clusters to be constitutive, and transcriptional analysis of the triple-deletion strain containing only extABCD detected no significant changes in expression of known redox proteins or pili components. These genetic experiments reveal new outer membrane conduit complexes necessary for growth of G. sulfurreducens , depending on the available extracellular electron acceptor.

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