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.

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 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 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 Helicobacter pylori Physiology Predicted from Genomic Comparison of Two Strains

1999 ◽  
Vol 63 (3) ◽  
pp. 675-707 ◽  
Author(s):  
Peter Doig ◽  
Boudewijn L. de Jonge ◽  
Richard A. Alm ◽  
Eric D. Brown ◽  
Maria Uria-Nickelsen ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
Sulfur Metabolism ◽  
Outer Membrane Proteins ◽  
Anaerobic Respiration ◽  
Phase Variation ◽  
Carbohydrate Utilization ◽  
Wide Range ◽  
H Pylori

SUMMARY Helicobacter pylori is a gram-negative bacteria which colonizes the gastric mucosa of humans and is implicated in a wide range of gastroduodenal diseases. This paper reviews the physiology of this bacterium as predicted from the sequenced genomes of two unrelated strains and reconciles these predictions with the literature. In general, the predicted capabilities are in good agreement with reported experimental observations. H. pylori is limited in carbohydrate utilization and will use amino acids, for which it has transporter systems, as sources of carbon. Energy can be generated by fermentation, and the bacterium possesses components necessary for both aerobic and anaerobic respiration. Sulfur metabolism is limited, whereas nitrogen metabolism is extensive. There is active uptake of DNA via transformation and ample restriction-modification activities. The cell contains numerous outer membrane proteins, some of which are porins or involved in iron uptake. Some of these outer membrane proteins and the lipopolysaccharide may be regulated by a slipped-strand repair mechanism which probably results in phase variation and plays a role in colonization. In contrast to a commonly held belief that H. pylori is a very diverse species, few differences were predicted in the physiology of these two unrelated strains, indicating that host and environmental factors probably play a significant role in the outocme of H. pylori-related disease.

scholarly journals The Conservation of Low Complexity Regions in Bacterial Proteins Depends on the Pathogenicity of the Strain and Subcellular Location of the Protein

Genes ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 451
Author(s):  
Pablo Mier ◽  
Miguel A. Andrade-Navarro
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Bacterial Species ◽  
Outer Membrane Proteins ◽  
Subcellular Location ◽  
Low Complexity ◽  
Extracellular Proteins ◽  
Bacterial Strains ◽  
Bacterial Proteins ◽  
Protein Subcellular Location

Low complexity regions (LCRs) in proteins are characterized by amino acid frequencies that differ from the average. These regions evolve faster and tend to be less conserved between homologs than globular domains. They are not common in bacteria, as compared to their prevalence in eukaryotes. Studying their conservation could help provide hypotheses about their function. To obtain the appropriate evolutionary focus for this rapidly evolving feature, here we study the conservation of LCRs in bacterial strains and compare their high variability to the closeness of the strains. For this, we selected 20 taxonomically diverse bacterial species and obtained the completely sequenced proteomes of two strains per species. We calculated all orthologous pairs for each of the 20 strain pairs. Per orthologous pair, we computed the conservation of two types of LCRs: compositionally biased regions (CBRs) and homorepeats (polyX). Our results show that, in bacteria, Q-rich CBRs are the most conserved, while A-rich CBRs and polyA are the most variable. LCRs have generally higher conservation when comparing pathogenic strains. However, this result depends on protein subcellular location: LCRs accumulate in extracellular and outer membrane proteins, with conservation increased in the extracellular proteins of pathogens, and decreased for polyX in the outer membrane proteins of pathogens. We conclude that these dependencies support the functional importance of LCRs in host–pathogen interactions.

Sign in / Sign up

Export Citation Format

Share Document