Rieske non-heme iron oxygenase (RO) family, 2-Oxoquinoline 8-monooxygenase (OMO) and Carbazole 1,9a-dioxygenase (CARDO) subfamily, N-terminal Rieske domain of the oxygenase alpha subunit; ROs comprise a large class of aromatic ring-hydroxylating dioxygenases that enable microorganisms to tolerate and utilize aromatic compounds for growth. The oxygenase alpha subunit contains an N-terminal Rieske domain with an [2Fe-2S] cluster and a C-terminal catalytic domain with a mononuclear Fe(II) binding site. The Rieske [2Fe-2S] cluster accepts electrons from a reductase or ferredoxin component and transfers them to the mononuclear iron for catalysis. OMO catalyzes the NADH-dependent oxidation of the N-heterocyclic aromatic compound 2-oxoquinoline to 8-hydroxy-2-oxoquinoline, the second step in the bacterial degradation of quinoline. OMO consists of a reductase component (OMR) and an oxygenase component (OMO) that together function to shuttle electrons from the reduced pyridine nucleotide to the active site of OMO, where O2 activation and 2-oxoquinoline hydroxylation occurs. CARDO, which contains oxygenase (CARDO-O), ferredoxin (CARDO-F) and ferredoxin reductase (CARDO-R) components, catalyzes the dihydroxylation at the C1 and C9a positions of carbazole. The oxygenase component of OMO and CARDO contain only alpha subunits arranged in a trimeric structure.
Jiyao W et al.(2023). "The conserved domain database in 2023.",