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Anammox organism KSU-1 expresses a novel His/DOPA ligated cytochrome c.

Authors
  • Hira, Daisuke1
  • Kitamura, Ryuji2
  • Nakamura, Teruya3
  • Yamagata, Yuriko4
  • Furukawa, Kenji5
  • Fujii, Takao2
  • 1 Department of Applied Life Science, Faculty of Biotechnology and Life Science, Sojo University, 4-22-1 Ikeda, Kumamoto 860-0082, Japan. Electronic address: [email protected] , (Japan)
  • 2 Department of Applied Life Science, Faculty of Biotechnology and Life Science, Sojo University, 4-22-1 Ikeda, Kumamoto 860-0082, Japan. , (Japan)
  • 3 Department of Structural Biology, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-Honmachi, Kumamoto 862-0973, Japan; Priority Organization for Innovation and Excellence, Kumamoto University, Kumamoto 862-0973, Japan. , (Japan)
  • 4 Department of Structural Biology, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-Honmachi, Kumamoto 862-0973, Japan. , (Japan)
  • 5 Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan. , (Japan)
Type
Published Article
Journal
Journal of Molecular Biology
Publisher
Elsevier
Publication Date
Feb 23, 2018
Identifiers
DOI: 10.1016/j.jmb.2018.02.017
PMID: 29481839
Source
Medline
Keywords
License
Unknown

Abstract

Anammox is a bacterial energy metabolic process that forms N2 gas from nitrite and ammonium ions. The enzymatic mechanisms of anammox have been gradually revealed; however, the electron transport chain in anammox bacteria remains poorly understood. In the present study, we purified and characterized two low-molecular-weight c-type cytochromes from an enriched culture of the anammox bacterium strain, KSU-1. Their genes, KSU1_B0428 and KSU1_C0855, were identified in the KSU-1 genome, and their recombinant proteins were characterized. KSU1_B0428 is a typical c-type cytochrome with a His/Met coordinated heme, acting as an electron transfer protein. In contrast, KSU1_C0855 could not be assigned as a known cytochrome and its heme was suggested to have an uncommon axial ligand set. Crystal structural analyses of C0855 clearly showed that its heme iron is coordinated by His15 as a fifth ligand. Moreover, the sixth coordination site is occupied by the aromatic ring of Tyr60, and an unassignable electron density that is inseparable with that of aromatic carbon of Tyr60 was found. The additional electron density was assigned to an O atom by molecular mass analyses. Therefore, Tyr60 would be chemically modified to 3,4-dihydroxyphenylalanine (DOPA) and bound to the Fe atom. We revealed that an anammox bacterium strain KSU-1 expresses a novel cytochrome c having an unprecedented His/DOPA coordinating heme. The expression of the novel c-type cytochrome might be required for the redox reaction of the anammox process.

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