scholarly journals Bespoke Biomolecular Wires for Transmembrane Electron Transfer: Spontaneous Assembly of a Functionalized Multiheme Electron Conduit

2021 ◽  
Vol 12 ◽  
Author(s):  
Samuel E. H. Piper ◽  
Marcus J. Edwards ◽  
Jessica H. van Wonderen ◽  
Carla Casadevall ◽  
Anne Martel ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Outer Membrane ◽  
Lipid Bilayer ◽  
Microbial Fuel Cells ◽  
Shewanella Oneidensis ◽  
Membrane Lipid ◽  
Electron Transfer Pathway ◽  
Redox Partners ◽  
Membrane Lipid Bilayer

Shewanella oneidensis exchanges electrons between cellular metabolism and external redox partners in a process that attracts much attention for production of green electricity (microbial fuel cells) and chemicals (microbial electrosynthesis). A critical component of this pathway is the outer membrane spanning MTR complex, a biomolecular wire formed of the MtrA, MtrB, and MtrC proteins. MtrA and MtrC are decaheme cytochromes that form a chain of close-packed hemes to define an electron transfer pathway of 185 Å. MtrA is wrapped inside MtrB for solubility across the outer membrane lipid bilayer; MtrC sits outside the cell for electron exchange with external redox partners. Here, we demonstrate tight and spontaneous in vitro association of MtrAB with separately purified MtrC. The resulting complex is comparable with the MTR complex naturally assembled by Shewanella in terms of both its structure and rates of electron transfer across a lipid bilayer. Our findings reveal the potential for building bespoke electron conduits where MtrAB combines with chemically modified MtrC, in this case, labeled with a Ru-dye that enables light-triggered electron injection into the MtrC heme chain.

The Power of Asymmetry: Architecture and Assembly of the Gram-Negative Outer Membrane Lipid Bilayer

2016 ◽  
Vol 70 (1) ◽  
pp. 255-278 ◽  
Author(s):  
Jeremy C. Henderson ◽  
Shawn M. Zimmerman ◽  
Alexander A. Crofts ◽  
Joseph M. Boll ◽  
Lisa G. Kuhns ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Lipid Bilayer ◽  
Membrane Lipid ◽  
Gram Negative ◽  
Membrane Lipid Bilayer

scholarly journals Relationship between the density distribution of intramembrane particles and electron transfer in the mitochondrial inner membrane as revealed by cholesterol incorporation.

1982 ◽  
Vol 94 (2) ◽  
pp. 387-393 ◽  
Author(s):  
H Schneider ◽  
M Höchli ◽  
C R Hackenbrock
Keyword(s):  
Electron Transfer ◽  
Surface Area ◽  
Lipid Bilayer ◽  
Average Distance ◽  
Membrane Lipid ◽  
Membrane Bilayer ◽  
Inner Membrane ◽  
Intramembrane Particles ◽  
Mitochondrial Inner Membrane ◽  
Membrane Lipid Bilayer

A low pH method of liposome-membrane fusion (Schneider et al., 1980, Proc. Natl. Acad. Sci. U. S. A. 77:442) was used to enrich the mitochondrial inner membrane lipid bilayer 30-700% with exogenous phospholipid and cholesterol. By varying the phospholipid-to-cholesterol ratio of the liposomes it was possible to incorporate specific amounts of cholesterol (up to 44 mol %) into the inner membrane bilayer in a controlled fashion. The membrane surface area increased proportionally to the increase in total membrane bilayer lipid. Inner membrane enriched with phospholipid only, or with phospholipid plus cholesterol up to 20 mol %, showed randomly distributed intramembrane particles (integral proteins) in the membrane plane, and the average distance between intramembrane particles increased proportionally to the amount of newly incorporated lipid. Membranes containing between 20 and 27 mol % cholesterol exhibited small clusters of intramembrane particles while cholesterol contents above 27 mol % resulted in larger aggregations of intramembrane particles. In phospholipid-enriched membranes with randomly dispersed intramembrane particles, electron transfer activities from NADH- and succinate-dehydrogenase to cytochrome c decreased proportionally to the increase in distance between the particles. In contrast, these electron-transfer activities increased with decreasing distances between intramembrane particles brought about by cholesterol incorporation. These results indicate that (a) catalytically interacting redox components in the mitochondrial inner membrane such as the dehydrogenase complexes, ubiquinone, and heme proteins are independent, laterally diffusible components; (b) the average distance between these redox components is effected by the available surface area of the membrane lipid bilayer; and (c) the distance over which redox components diffuse before collision and electron transfer mediates the rate of such transfer.

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 Outer membrane permeability: Antimicrobials and diverse nutrients bypass porins in Pseudomonas aeruginosa

2021 ◽  
Vol 118 (31) ◽  
pp. e2107644118
Author(s):  
Johanna Ude ◽  
Vishwachi Tripathi ◽  
Julien M. Buyck ◽  
Sandra Söderholm ◽  
Olivier Cunrath ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Outer Membrane ◽  
Lipid Bilayer ◽  
Membrane Lipid ◽  
Major Pathway ◽  
Unique Type ◽  
Carboxylate Groups ◽  
Membrane Lipid Bilayer ◽  
Outer Membrane Permeability

Gram-negative bacterial pathogens have an outer membrane that restricts entry of molecules into the cell. Water-filled protein channels in the outer membrane, so-called porins, facilitate nutrient uptake and are thought to enable antibiotic entry. Here, we determined the role of porins in a major pathogen, Pseudomonas aeruginosa, by constructing a strain lacking all 40 identifiable porins and 15 strains carrying only a single unique type of porin and characterizing these strains with NMR metabolomics and antimicrobial susceptibility assays. In contrast to common assumptions, all porins were dispensable for Pseudomonas growth in rich medium and consumption of diverse hydrophilic nutrients. However, preferred nutrients with two or more carboxylate groups such as succinate and citrate permeated poorly in the absence of porins. Porins provided efficient translocation pathways for these nutrients with broad and overlapping substrate selectivity while efficiently excluding all tested antibiotics except carbapenems, which partially entered through OprD. Porin-independent permeation of antibiotics through the outer-membrane lipid bilayer was hampered by carboxylate groups, consistent with our nutrient data. Together, these results challenge common assumptions about the role of porins by demonstrating porin-independent permeation of the outer-membrane lipid bilayer as a major pathway for nutrient and drug entry into the bacterial cell.

scholarly journals PHLIP ARG-Mutant Interactions with the Membrane Lipid Bilayer

2021 ◽  
Vol 120 (3) ◽  
pp. 232a
Author(s):  
Hannah M. Visca ◽  
Oleg A. Andreev ◽  
Yana K. Reshetnyak
Keyword(s):  
Lipid Bilayer ◽  
Membrane Lipid ◽  
Membrane Lipid Bilayer

scholarly journals A Hybrid Extracellular Electron Transfer Pathway Enhances the Survival of Vibrio natriegens

2020 ◽  
Vol 86 (19) ◽  
Author(s):  
Bridget E. Conley ◽  
Matthew T. Weinstock ◽  
Daniel R. Bond ◽  
Jeffrey A. Gralnick
Keyword(s):  
Electron Transfer ◽  
Shewanella Oneidensis ◽  
Anaerobic Respiration ◽  
Basic Research ◽  
Extracellular Electron Transfer ◽  
Content Type ◽  
Electron Transfer Pathway ◽  
Sedimentary Environments ◽  
Genetic Potential ◽  
Iron And Manganese

ABSTRACT Vibrio natriegens is the fastest-growing microorganism discovered to date, making it a useful model for biotechnology and basic research. While it is recognized for its rapid aerobic metabolism, less is known about anaerobic adaptations in V. natriegens or how the organism survives when oxygen is limited. Here, we describe and characterize extracellular electron transfer (EET) in V. natriegens, a metabolism that requires movement of electrons across protective cellular barriers to reach the extracellular space. V. natriegens performs extracellular electron transfer under fermentative conditions with gluconate, glucosamine, and pyruvate. We characterized a pathway in V. natriegens that requires CymA, PdsA, and MtrCAB for Fe(III) citrate and Fe(III) oxide reduction, which represents a hybrid of strategies previously discovered in Shewanella and Aeromonas. Expression of these V. natriegens genes functionally complemented Shewanella oneidensis mutants. Phylogenetic analysis of the inner membrane quinol dehydrogenases CymA and NapC in gammaproteobacteria suggests that CymA from Shewanella diverged from Vibrionaceae CymA and NapC. Analysis of sequenced Vibrionaceae revealed that the genetic potential to perform EET is conserved in some members of the Harveyi and Vulnificus clades but is more variable in other clades. We provide evidence that EET enhances anaerobic survival of V. natriegens, which may be the primary physiological function for EET in Vibrionaceae. IMPORTANCE Bacteria from the genus Vibrio occupy a variety of marine and brackish niches with fluctuating nutrient and energy sources. When oxygen is limited, fermentation or alternative respiration pathways must be used to conserve energy. In sedimentary environments, insoluble oxide minerals (primarily iron and manganese) are able to serve as electron acceptors for anaerobic respiration by microorganisms capable of extracellular electron transfer, a metabolism that enables the use of these insoluble substrates. Here, we identify the mechanism for extracellular electron transfer in Vibrio natriegens, which uses a combination of strategies previously identified in Shewanella and Aeromonas. We show that extracellular electron transfer enhanced survival of V. natriegens under fermentative conditions, which may be a generalized strategy among Vibrio spp. predicted to have this metabolism.

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