Old yellow enzyme (OYE)-related FMN binding domain, group 4. Each monomer of OYE contains FMN as a non-covalently bound cofactor, uses NADPH as a reducing agent with oxygens, quinones, and alpha,beta-unsaturated aldehydes and ketones, and can act as electron acceptors in the catalytic reaction. Other members of OYE family include trimethylamine dehydrogenase, 2,4-dienoyl-CoA reductase, enoate reductase, pentaerythriol tetranitrate reductase, xenobiotic reductase, and morphinone reductase.