Rieske non-heme iron oxygenase (RO) family, Choline monooxygenase (CMO) 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. CMO is a novel RO found in certain plants which catalyzes the first step in betaine synthesis. CMO is not found in animals or bacteria. In these organisms, the first step in betaine synthesis is catalyzed by either the membrane-bound choline dehydrogenase (CDH) or the soluble choline oxidase (COX).
Jiyao W et al.(2023). "The conserved domain database in 2023.",