Details

Autor(en) / Beteiligte

• Picciano, Angela L
• Crane, Brian R

Titel

A nitric oxide synthase-like protein from Synechococcus produces NO/NO 3 - from l-arginine and NADPH in a tetrahydrobiopterin- and Ca 2+ -dependent manner

Ist Teil von

• The Journal of biological chemistry, 2019-07, Vol.294 (27), p.10708

Ort / Verlag

United States

Erscheinungsjahr

2019

Quelle

MEDLINE

Beschreibungen/Notizen

• Nitric oxide synthases (NOSs) are heme-based monooxygenases that convert l-Arg to l-citrulline and nitric oxide (NO), a key signaling molecule and cytotoxic agent in mammals. Bacteria also contain NOS proteins, but the role of NO production within these organisms, where understood, differs considerably from that of mammals. For example, a NOS protein in the marine cyanobacterium sp. PCC 7335 (syNOS) has recently been proposed to function in nitrogen assimilation from l-Arg. syNOS retains the oxygenase (NOS ) and reductase (NOS ) domains present in mammalian NOS enzymes (mNOSs), but also contains an N-terminal globin domain (NOS ) homologous to bacterial flavohemoglobin proteins. Herein, we show that syNOS functions as a dimer and produces NO from l-Arg and NADPH in a tetrahydrobiopterin (H B)-dependent manner at levels similar to those produced by other NOSs but does not require Ca -calmodulin, which regulates NOS -mediated NOS reduction in mNOSs. Unlike other bacterial NOSs, syNOS cannot function with tetrahydrofolate and requires high Ca levels (>200 μm) for its activation. NOS converts NO to NO in the presence of O and NADPH; however, NOS did not protect strains against nitrosative stress, even in a mutant devoid of NO-protective flavohemoglobin. We also found that syNOS does not have NOS activity in (which lacks H B) and that the recombinant protein does not confer growth advantages on l-Arg as a nitrogen source. Our findings indicate that syNOS has both NOS and NO oxygenase activities, requires H B, and may play a role in Ca -mediated signaling.