scholarly journals Development of a proteoliposome model to probe transmembrane electron-transfer reactions

2012 ◽  
Vol 40 (6) ◽  
pp. 1257-1260 ◽  
Author(s):  
Gaye F. White ◽  
Zhi Shi ◽  
Liang Shi ◽  
Alice C. Dohnalkova ◽  
James K. Fredrickson ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Outer Membrane ◽  
Protein Complex ◽  
Methyl Viologen ◽  
Cation Exchanger ◽  
Shewanella Oneidensis ◽  
Model System ◽  
Electron Acceptors ◽  
Transfer Reactions ◽  
Electron Carrier

The mineral-respiring bacterium Shewanella oneidensis uses a protein complex, MtrCAB, composed of two decahaem cytochromes brought together inside a transmembrane porin to transport electrons across the outer membrane to a variety of mineral-based electron acceptors. A proteoliposome system has been developed that contains Methyl Viologen as an internalized electron carrier and valinomycin as a membrane-associated cation exchanger. These proteoliposomes can be used as a model system to investigate MtrCAB function.

scholarly journals Structural modeling of an outer membrane electron conduit from a metal-reducing bacterium suggests electron transfer via periplasmic redox partners

2018 ◽  
Vol 293 (21) ◽  
pp. 8103-8112 ◽  
Author(s):  
Marcus J. Edwards ◽  
Gaye F. White ◽  
Colin W. Lockwood ◽  
Matthew C. Lawes ◽  
Anne Martel ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Outer Membrane ◽  
Membrane Surface ◽  
Shewanella Oneidensis ◽  
Direct Interaction ◽  
Electron Acceptors ◽  
Scattering Data ◽  
Redox Partners ◽  
Mediated Electron Transfer ◽  
Tetraheme Cytochrome

Many subsurface microorganisms couple their metabolism to the reduction or oxidation of extracellular substrates. For example, anaerobic mineral-respiring bacteria can use external metal oxides as terminal electron acceptors during respiration. Porin–cytochrome complexes facilitate the movement of electrons generated through intracellular catabolic processes across the bacterial outer membrane to these terminal electron acceptors. In the mineral-reducing model bacterium Shewanella oneidensis MR-1, this complex is composed of two decaheme cytochromes (MtrA and MtrC) and an outer-membrane β-barrel (MtrB). However, the structures and mechanisms by which porin–cytochrome complexes transfer electrons are unknown. Here, we used small-angle neutron scattering (SANS) to study the molecular structure of the transmembrane complexes MtrAB and MtrCAB. Ab initio modeling of the scattering data yielded a molecular envelope with dimensions of ∼105 × 60 × 35 Å for MtrAB and ∼170 × 60 × 45 Å for MtrCAB. The shapes of these molecular envelopes suggested that MtrC interacts with the surface of MtrAB, extending ∼70 Å from the membrane surface and allowing the terminal hemes to interact with both MtrAB and an extracellular acceptor. The data also reveal that MtrA fully extends through the length of MtrB, with ∼30 Å being exposed into the periplasm. Proteoliposome models containing membrane-associated MtrCAB and internalized small tetraheme cytochrome (STC) indicate that MtrCAB could reduce Fe(III) citrate with STC as an electron donor, disclosing a direct interaction between MtrCAB and STC. Taken together, both structural and proteoliposome experiments support porin–cytochrome–mediated electron transfer via periplasmic cytochromes such as STC.

scholarly journals Mind the gap: diversity and reactivity relationships among multihaem cytochromes of the MtrA/DmsE family

2012 ◽  
Vol 40 (6) ◽  
pp. 1268-1273 ◽  
Author(s):  
Kathryn D. Bewley ◽  
Mackenzie A. Firer-Sherwood ◽  
Jee-Young Mock ◽  
Nozomi Ando ◽  
Catherine L. Drennan ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
Evolutionary Relationship ◽  
Shewanella Oneidensis ◽  
Anaerobic Respiration ◽  
Electron Acceptors ◽  
Protein Film ◽  
Protein Film Voltammetry

Shewanella oneidensis MR-1 has the ability to use many external terminal electron acceptors during anaerobic respiration, such as DMSO. The pathway that facilitates this electron transfer includes the decahaem cytochrome DmsE, a paralogue of the MtrA family of decahaem cytochromes. Although both DmsE and MtrA are decahaem cytochromes implicated in the long-range electron transfer across a ~300 Å (1 Å=0.1 nm) wide periplasmic ‘gap’, MtrA has been shown to be only 105 Å in maximal length. In the present paper, DmsE is further characterized via protein film voltammetry, revealing that the electrochemistry of the DmsE haem cofactors display macroscopic potentials lower than those of MtrA by 100 mV. It is possible this tuning of the redox potential of DmsE is required to shuttle electrons to the outer-membrane proteins specific to DMSO reduction. Other decahaem cytochromes found in S. oneidensis, such as the outer-membrane proteins MtrC, MtrF and OmcA, have been shown to have electrochemical properties similar to those of MtrA, yet possess a different evolutionary relationship.

Kinetics of electron-transfer reactions between transition-metal complexes and the methyl viologen radical cation

1988 ◽  
Vol 27 (17) ◽  
pp. 2932-2934 ◽  
Author(s):  
Kevin R. Howes ◽  
C. Greg Pippin ◽  
James C. Sullivan ◽  
Dan Meisel ◽  
James H. Espenson ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Transition Metal ◽  
Metal Complexes ◽  
Radical Cation ◽  
Transition Metal Complexes ◽  
Methyl Viologen ◽  
Transfer Reactions ◽  
Electron Transfer Reactions ◽  
Kinetics Of

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

2002 ◽  
Vol 30 (4) ◽  
pp. 658-662 ◽  
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.

scholarly journals Involvement of theShewanella oneidensisDecaheme Cytochrome MtrA in the Periplasmic Stability of the β-Barrel Protein MtrB

2010 ◽  
Vol 77 (4) ◽  
pp. 1520-1523 ◽  
Author(s):  
Marcus Schicklberger ◽  
Clemens Bücking ◽  
Bjoern Schuetz ◽  
Heinrich Heide ◽  
Johannes Gescher
Keyword(s):  
Gene Expression ◽  
Outer Membrane ◽  
Quantitative Pcr ◽  
Protein Complex ◽  
Iron Reduction ◽  
Heterologous Gene Expression ◽  
Shewanella Oneidensis ◽  
Heterologous Gene ◽  
Dissimilatory Iron Reduction ◽  
Membrane Spanning

ABSTRACTTheShewanella oneidensisouter membrane β-barrel protein MtrB is part of a membrane-spanning protein complex (MtrABC) which is necessary for dissimilatory iron reduction. Quantitative PCR, heterologous gene expression, and mutant studies indicated that MtrA is required for periplasmic stability of MtrB. DegP depletion compensated for this MtrA dependence.

scholarly journals Isolation of a High-Affinity Functional Protein Complex between OmcA and MtrC: Two Outer Membrane Decaheme c-Type Cytochromes of Shewanella oneidensis MR-1

2006 ◽  
Vol 188 (13) ◽  
pp. 4705-4714 ◽  
Author(s):  
Liang Shi ◽  
Baowei Chen ◽  
Zheming Wang ◽  
Dwayne A. Elias ◽  
M. Uljana Mayer ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Protein Complex ◽  
Specific Activity ◽  
Reductase Activity ◽  
Shewanella Oneidensis ◽  
Stable Complex ◽  
Wild Type ◽  
Functional Protein ◽  
Transport Pathway ◽  
High Affinity

ABSTRACT Shewanella oneidensis MR-1 is a facultatively anaerobic bacterium capable of using soluble and insoluble forms of manganese [Mn(III/IV)] and iron [Fe(III)] as terminal electron acceptors during anaerobic respiration. To assess the structural association of two outer membrane-associated c-type decaheme cytochromes (i.e., OmcA [SO1779] and MtrC [SO1778]) and their ability to reduce soluble Fe(III)-nitrilotriacetic acid (NTA), we expressed these proteins with a C-terminal tag in wild-type S. oneidensis and a mutant deficient in these genes (i.e., ΔomcA mtrC). Endogenous MtrC copurified with tagged OmcA in wild-type Shewanella, suggesting a direct association. To further evaluate their possible interaction, both proteins were purified to near homogeneity following the independent expression of OmcA and MtrC in the ΔomcA mtrC mutant. Each purified cytochrome was confirmed to contain 10 hemes and exhibited Fe(III)-NTA reductase activity. To measure binding, MtrC was labeled with the multiuse affinity probe 4′,5′-bis(1,3,2-dithioarsolan-2-yl)fluorescein (1,2-ethanedithiol)2, which specifically associates with a tetracysteine motif engineered at the C terminus of MtrC. Upon titration with OmcA, there was a marked increase in fluorescence polarization indicating the formation of a high-affinity protein complex (Kd < 500 nM) between MtrC and OmcA whose binding was sensitive to changes in ionic strength. Following association, the OmcA-MtrC complex was observed to have enhanced Fe(III)-NTA reductase specific activity relative to either protein alone, demonstrating that OmcA and MtrC can interact directly with each other to form a stable complex that is consistent with their role in the electron transport pathway of S. oneidensis MR-1.

Light-induced electron-transfer reactions involving the tris(2,2'-bipyridine)ruthenium dication and related complexes. I. The bis(2,2'-bipyridine)(diethyl 2,2'-bipyridine-4,4'-dicarboxylate)ruthenium dication

1980 ◽  
Vol 33 (8) ◽  
pp. 1643 ◽  
Author(s):  
O Johansen ◽  
A Launikonis ◽  
AWH Mau ◽  
WHF Sasse
Keyword(s):  
Electron Transfer ◽  
Methyl Viologen ◽  
Platinum Catalyst ◽  
Ethylenediaminetetraacetic Acid ◽  
Ester Group ◽  
Transfer Reactions ◽  
Acid Methyl ◽  
Water Rate ◽  
Electron Withdrawal ◽  
Bimolecular Quenching

Irradiation of the bis(2,2'-bipyridine)(diethyl 2,2'-bipyridine-4,4'- dicarboxylate)ruthenium(II) dication (2c) in water, in the presence of ethylenediaminetetraacetic acid, methyl viologen and a platinum catalyst, produces hydrogen at about one-tenth the rate observed with Ru(bpy)32+. This decrease is ascribed to electron withdrawal by the ester group in (2c) and to bimolecular quenching of photo-excited (2c) by water (rate constant 9.3 × 104 1. mol-1 s-1), which follows (in ethanol) Stern-Volmer kinetics (KSV 9.5 x 10-2 1. mol-1).

Sign in / Sign up

Export Citation Format

Share Document