Redox Linked Flavin Sites in Extracellular Decaheme Proteins Involved in Microbe-Mineral Electron Transfer

Sci Rep. 2015 Jul 1;5:11677. doi: 10.1038/srep11677.

Abstract

Extracellular microbe-mineral electron transfer is a major driving force for the oxidation of organic carbon in many subsurface environments. Extracellular multi-heme cytochromes of the Shewenella genus play a major role in this process but the mechanism of electron exchange at the interface between cytochrome and acceptor is widely debated. The 1.8 Å x-ray crystal structure of the decaheme MtrC revealed a highly conserved CX8C disulfide that, when substituted for AX8A, severely compromised the ability of S. oneidensis to grow under aerobic conditions. Reductive cleavage of the disulfide in the presence of flavin mononucleotide (FMN) resulted in the reversible formation of a stable flavocytochrome. Similar results were also observed with other decaheme cytochromes, OmcA, MtrF and UndA. The data suggest that these decaheme cytochromes can transition between highly reactive flavocytochromes or less reactive cytochromes, and that this transition is controlled by a redox active disulfide that responds to the presence of oxygen.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Aerobiosis
  • Amino Acid Motifs
  • Amino Acid Sequence
  • Anaerobiosis
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / metabolism*
  • Crystallography, X-Ray
  • Cytochromes / metabolism
  • Disulfides / metabolism
  • Electron Transport
  • Electrophoresis, Polyacrylamide Gel
  • Flavins / metabolism*
  • Glutathione / metabolism
  • Heme / metabolism
  • Minerals / metabolism*
  • Oxidation-Reduction
  • Phylogeny
  • Sequence Alignment
  • Shewanella / growth & development
  • Shewanella / metabolism*
  • Spectrometry, Fluorescence
  • Spectrophotometry, Ultraviolet

Substances

  • Bacterial Proteins
  • Cytochromes
  • Disulfides
  • Flavins
  • Minerals
  • Heme
  • Glutathione