Homologous Superfamily

Riboflavin synthase-like beta-barrel (IPR017938)

Short name: Riboflavin_synthase-like_b-brl

Overlapping entries


This superfamily represents a structural domain with a closed beta-barrel fold with greek-key topology. Domains with this structure can be found in the following proteins:

  • Riboflavin synthase, which contains two homologous domains of this structure [PMID: 11377200].
  • The FAD-binding (N-terminal) domain of ferredoxin reductase (flavodoxin reductase), where the FAD-binding domain is coupled with a NADP-binding domain of the alpha/beta class [PMID: 9149148].
  • The FAD-binding domain of NADPH-cytochrome p450 reductase; however, this domain has an additional alpha-helical domain inserted into it [PMID: 9237990].

Riboflavin synthase (EC: catalyses the final step in the biosynthesis of vitamin B2, namely the dismutation of two molecules of 6,7-dimethyl-8-ribityllumazine to yield riboflavin and 4-(1-D-ribitylamino)-5-amino-2,6-dihydroxypyrimidine (which is recycled) [PMID: 18298940].

Flavins can act as primary and secondary emitters in bacterial luminescence. Lumazine proteins are involved in the bioluminescence of certain marine bacteria. These proteins are catalytically inactive, but they resemble riboflavin synthase [PMID: 18602927]. Lumazine is non-covalently bound to the fluorophore 6,7-dimethyl-8-ribityllumazine, which is the substrate of riboflavin synthase.

Ferredoxin reductase is a FAD-containing oxidoreductase that transports electrons between flavodoxin or ferredoxin and NADPH. In Escherichia coli, ferredoxin reductase together with flavodoxin is involved in the reductive activation of three enzymes: cobalamin-dependent methionine synthase, pyruvate formate lyase and anaerobic ribonucleotide reductase [PMID: 9149148]. An additional function for the oxidoreductase appears to be to protect the bacteria against oxygen radicals. The beta-barrel domain found in ferredoxin reductase is similar to that found in: NAD(P)H:flavin oxidoreductase [PMID: 10353815], the core domain of nitrate reductase [PMID: 7760334], cytochrome b5 reductase [PMID: 15502298], phthalate dioxygenase reductase (which contains an additional 2Fe-2S ferredoxin domain) [PMID: 1280857], benzoate dioxygenase reductase [PMID: 12051836], the PyrK subunit of dihydroorotate dehydrogenase B [PMID: 11188687], the central domain of flavohaemoglobin (which contains an additional globin domain) [PMID: 11964402], and methane monooxygenase component C (MmoC) [PMID: 15379538].

Microsomal NADPH-cytochrome P450 reductase (EC: (CPR) (NADPH-haemoprotein reductase) is a membrane-bound protein that contains both FAD and FMN. CPR catalyses electron transfer from NADPH to all known microsomal cytochromes P450. The beta-barrel domain found in NADPH-cytochrome p450 reductase is similar to that found in: sulphite reductase flavoprotein [PMID: 10860732], and the FAD/NADP+ domain of neuronal nitric-oxide synthase [PMID: 11473123].

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.