scholarly journals Ultrafast Light-Driven Electron Transfer in a Ru(II)tris(bipyridine)-Labeled Multiheme Cytochrome

2019 ◽  
Vol 141 (38) ◽  
pp. 15190-15200 ◽  
Author(s):  
Jessica H. van Wonderen ◽  
Christopher R. Hall ◽  
Xiuyun Jiang ◽  
Katrin Adamczyk ◽  
Antoine Carof ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Multiheme Cytochrome

scholarly journals Electron Transfer Pathways in a Multiheme Cytochrome MtrF

2017 ◽  
Vol 57 (3) ◽  
pp. 151-152
Author(s):  
Hiroshi WATANABE ◽  
Yuki YAMASHITA ◽  
Hiroshi ISHIKITA
Keyword(s):  
Electron Transfer ◽  
Electron Transfer Pathways ◽  
Multiheme Cytochrome

scholarly journals Geobacter sulfurreducensextracellular multiheme cytochrome PgcA facilitates respiration to Fe(III) oxides but not electrodes

2017 ◽  
Author(s):  
Lori Zacharoff ◽  
Dana Morrone ◽  
Daniel R. Bond
Keyword(s):  
Electron Transfer ◽  
Metal Oxides ◽  
Solid Phase ◽  
Shewanella Oneidensis ◽  
Helical Structure ◽  
Geobacter Sulfurreducens ◽  
Extracellular Electron Transfer ◽  
Mineral Surfaces ◽  
Electrode Surfaces ◽  
Multiheme Cytochrome

AbstractExtracellular cytochromes are hypothesized to facilitate the final steps of electron transfer between the outer membrane of the metal-reducing bacteriumGeobacter sulfurreducensand solid-phase electron acceptors such as metal oxides and electrode surfaces during the course of respiration. The trihemec-type cytochrome PgcA exists in the extracellular space ofG. sulfurreducens, and is one of many multihemec-type cytochromes known to be loosely bound to the bacterial outer surface. Deletion ofpgcAusing a markerless method resulted in mutants unable to transfer electrons to Fe(III) and Mn(IV) oxides; yet the same mutants maintained the ability to respire electrode surfaces and soluble Fe(III) citrate. When expressed and purified fromShewanella oneidensis, PgcA demonstrated a primarily alpha helical structure, three bound hemes, and was processed into a shorter 41 kDa form lacking the lipodomain. Purified PgcA bound Fe(III) oxides, but not magnetite, and when PgcA was added to cell suspensions ofG. sulfurreducens,PgcA accelerated Fe(III) reduction similar to addition of FMN. Addition of soluble PgcA to ∆pgcAmutants also restored Fe(III) reduction. This report highlights a distinction between proteins involved in extracellular electron transfer to metal oxides and poised electrodes, and suggests a specific role for PgcA in facilitating electron transfer at mineral surfaces.

scholarly journals Electron transfer pathways in a multiheme cytochrome MtrF

2017 ◽  
Vol 114 (11) ◽  
pp. 2916-2921 ◽  
Author(s):  
Hiroshi C. Watanabe ◽  
Yuki Yamashita ◽  
Hiroshi Ishikita
Keyword(s):  
Electron Transfer ◽  
Binding Sites ◽  
Heme Binding ◽  
Binding Domains ◽  
Poisson Boltzmann ◽  
Electron Transfer Pathways ◽  
Poisson Boltzmann Equation ◽  
Dynamics Simulations ◽  
Flavin Binding ◽  
Multiheme Cytochrome

In MtrF, an outer-membrane multiheme cytochrome, the 10 heme groups are arranged in heme binding domains II and IV along the pseudo-C2 axis, forming the electron transfer (ET) pathways. Previous reports based on molecular dynamics simulations showed that the redox potential (Em) values for the heme pairs located in symmetrical positions in domains II and IV were similar, forming bidirectional ET pathways [Breuer M, Zarzycki P, Blumberger J, Rosso KM (2012) J Am Chem Soc 134(24):9868–9871]. Here, we present the Em values of the 10 hemes in MtrF, solving the linear Poisson–Boltzmann equation and considering the protonation states of all titratable residues and heme propionic groups. In contrast to previous studies, the Em values indicated that the ET is more likely to be downhill from domain IV to II because of localization of acidic residues in domain IV. Reduction of hemes in MtrF lowered the Em values, resulting in switching to alternative downhill ET pathways that extended to the flavin binding sites. These findings present an explanation of how MtrF serves as an electron donor to extracellular substrates.

A light optical diffractometer for electron microscopical images operating in line

1978 ◽  
Vol 36 (1) ◽  
pp. 86-87
Author(s):  
P. Bonhomme ◽  
A. Beorchia
Keyword(s):  
Electron Microscopy ◽  
Electron Transfer ◽  
Electron Microscope ◽  
Image Converter ◽  
Coherent Light ◽  
Spatial Filters ◽  
Electron Image ◽  
Electron Microscopical ◽  
Working Parameters ◽  
Amorphous Part

We have already described (1.2.3) a device using a pockel's effect light valve as a microscopical electron image converter. This converter can be read out with incoherent or coherent light. In the last case we can set in line with the converter an optical diffractometer. Now, electron microscopy developments have pointed out different advantages of diffractometry. Indeed diffractogram of an image of a thin amorphous part of a specimen gives information about electron transfer function and a single look at a diffractogram informs on focus, drift, residual astigmatism, and after standardizing, on periods resolved (4.5.6). These informations are obvious from diffractogram but are usualy obtained from a micrograph, so that a correction of electron microscope parameters cannot be realized before recording the micrograph. Diffractometer allows also processing of images by setting spatial filters in diffractogram plane (7) or by reconstruction of Fraunhofer image (8). Using Electrotitus read out with coherent light and fitted to a diffractometer; all these possibilities may be realized in pseudoreal time, so that working parameters may be optimally adjusted before recording a micrograph or before processing an image.

Flavin radicals, conformational sampling and robust design principles in interprotein electron transfer: the trimethylamine dehydrogenase-electron-transferring flavoprotein complex

2004 ◽  
Vol 71 ◽  
pp. 1-14
Author(s):  
David Leys ◽  
Jaswir Basran ◽  
François Talfournier ◽  
Kamaldeep K. Chohan ◽  
Andrew W. Munro ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Kinetic Studies ◽  
Molecular Assembly ◽  
Conformational Sampling ◽  
Trimethylamine Dehydrogenase ◽  
Key Residues ◽  
Electron Transferring Flavoprotein ◽  
Electron Transfer Complex

TMADH (trimethylamine dehydrogenase) is a complex iron-sulphur flavoprotein that forms a soluble electron-transfer complex with ETF (electron-transferring flavoprotein). The mechanism of electron transfer between TMADH and ETF has been studied using stopped-flow kinetic and mutagenesis methods, and more recently by X-ray crystallography. Potentiometric methods have also been used to identify key residues involved in the stabilization of the flavin radical semiquinone species in ETF. These studies have demonstrated a key role for 'conformational sampling' in the electron-transfer complex, facilitated by two-site contact of ETF with TMADH. Exploration of three-dimensional space in the complex allows the FAD of ETF to find conformations compatible with enhanced electronic coupling with the 4Fe-4S centre of TMADH. This mechanism of electron transfer provides for a more robust and accessible design principle for interprotein electron transfer compared with simpler models that invoke the collision of redox partners followed by electron transfer. The structure of the TMADH-ETF complex confirms the role of key residues in electron transfer and molecular assembly, originally suggested from detailed kinetic studies in wild-type and mutant complexes, and from molecular modelling.

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