Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 106, Issue 38, Pages 16221-16226Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0908443106
Keywords
heme protein; iron-sulfur cluster; reductase; tetrahydrobiopterin; tetrahydrofolate
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Funding
- Miller Institute for Basic Science
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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 O-2 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.
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