Efflux pump; part of the gene cluster that mediates the biosynthesis of viridicatumtoxin, a tetracycline-like fungal meroterpenoid with a unique, fused spirobicyclic ring system (PubMed:20534346). Viridicatumtoxin and its derivative, viridicatumtoxin B, exhibit anti-methicillin-resistant Staphylococcus aureus (anti-MRSA) activity (PubMed:19168978). Moreover, viridicatumtoxin and a C2 acetyl analog, spirohexaline, have been demonstrated to inhibit bacterial undecaprenyl diphosphate synthase, a potential new target for antibiotic development (PubMed:27049441). Belongs to the major facilitator superfamily.