Assembly of Dimeric Variants of Coumermycins by Tandem Action of the Four Biosynthetic Enzymes CouL, CouM, CouP, and NovN
文摘
Coumermycin A1 is a member of the aminocoumarin family of antibiotics. Unlike its structuralrelatives, novobiocin and clorobiocin, coumermycin A1 is a dimer built on a 3-methyl-2,4-dicarboxypyrrolescaffold and bears two decorated noviose sugar components which are the putative target binding motifsfor DNA gyrase. Starting with this scaffold, we have utilized the ligase CouL for mono- and bisamideformation with aminocoumarins to provide substrates for the glycosyltransferase CouM. CouM wassubsequently shown to catalyze mono- and bisnoviosylation of the resulting CouL products. CouP wasshown to possess 4'-O-methyltransferase activity on products from tandem CouL, CouM assays. A fourthenzyme, NovN, the 3'-O-carbamoyltransferase from the novobiocin operon, was then able to carbamoylateeither or both arms of the CouP product. The tandem action of CouL, CouM, CouP, and NovN thusgenerates a biscarbamoyl analogue of the pseudodimer coumermycin A1. Starting from alternative dicarboxyscaffolds, these four enzymes can be utilized in tandem to create additional variants of dimericaminocoumarin antibiotics.