NO formation by a catalytically self-sufficient bacterial nitric oxide synthase from Sorangium cellulosum

Proc Natl Acad Sci U S A. 2009 Sep 22;106(38):16221-6. doi: 10.1073/pnas.0908443106. Epub 2009 Sep 10.


The role of nitric oxide (NO) in the host response to infection and in cellular signaling is well established. Enzymatic synthesis of NO is catalyzed by the nitric oxide synthases (NOSs), which convert Arg into NO and citrulline using co-substrates O2 and NADPH. Mammalian NOS contains a flavin reductase domain (FAD and FMN) and a catalytic heme oxygenase domain (P450-type heme and tetrahydrobiopterin). Bacterial NOSs, while much less studied, were previously identified as only containing the heme oxygenase domain of the more complex mammalian NOSs. We report here on the characterization of a NOS from Sorangium cellulosum (both full-length, scNOS, and oxygenase domain, scNOSox). scNOS contains a catalytic, oxygenase domain similar to those found in the mammalian NOS and in other bacteria. Unlike the other bacterial NOSs reported to date, however, this protein contains a fused reductase domain. The scNOS reductase domain is unique for the entire NOS family because it utilizes a 2Fe2S cluster for electron transfer. scNOS catalytically produces NO and citrulline in the presence of either tetrahydrobiopterin or tetrahydrofolate. These results establish a bacterial electron transfer pathway used for biological NO synthesis as well as a unique flexibility in using different tetrahydropterin cofactors for this reaction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Binding Sites
  • Catalysis
  • Electron Spin Resonance Spectroscopy
  • Electron Transport
  • Electrophoresis, Polyacrylamide Gel
  • Heme / chemistry
  • Heme / metabolism
  • Kinetics
  • Models, Chemical
  • Molecular Sequence Data
  • Myxococcales / enzymology*
  • Myxococcales / genetics
  • NADP / chemistry
  • NADP / metabolism
  • Nitric Oxide / chemistry
  • Nitric Oxide / metabolism*
  • Nitric Oxide Synthase / genetics
  • Nitric Oxide Synthase / metabolism*
  • Oxidation-Reduction
  • Oxygen / chemistry
  • Oxygen / metabolism
  • Protein Binding
  • Sequence Homology, Amino Acid
  • Spectrophotometry, Ultraviolet
  • Substrate Specificity


  • Bacterial Proteins
  • Nitric Oxide
  • Heme
  • NADP
  • Nitric Oxide Synthase
  • Oxygen