Identification of a novel Arabidopsis thaliana nitric oxide-binding molecule with guanylate cyclase activity in vitro

While there is evidence of nitric oxide (NO)-dependent signalling via the second messenger cyclic guanosine 3′,5′-monophosphate (cGMP) in plants, guanylate cyclases (GCs), enzymes that catalyse the formation of cGMP from guanosine 5′-triphosphate (GTP) have until recently remained elusive and none of the candidates identified to-date are NO-dependent. Using both a GC and heme-binding domain specific (H-NOX) search motif, we have identified an Arabidopsis flavin monooxygenase (At1g62580) and shown electrochemically that it binds NO, has a higher affinity for NO than for O2 and that this molecule can generate cGMP from GTP in vitro in an NO-dependent manner.

► The Arabidopsis protein AtNOGC1 contains an H-NOX domain.
► AtNOGC1 binds O2 and NO at the same binding site.
► NO has a higher affinity for the AtNOGC1 heme site than O2.
► AtNOGC1 has nitric NO-inducible guanylate cyclase activity in vitro.