Covalent CouN7 Enzyme Intermediate for Acyl Group Shuttling in Aminocoumarin Biosynthesis

Carl J. Balibar, Sylvie Garneau-Tsodikova, Christopher T. Walsh

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


The last stages of assembly of the aminocoumarin antibiotics, clorobiocin and coumermycin A1, which target the GyrB subunits of bacterial DNA gyrase, involve enzymatic transfer of the pyrrolyl-2-carbonyl acyl group from a carrier protein (CloN1/CouN1) to the 3′-OH of the noviosyl moiety of the antibiotic scaffold. The enzyme, CouN7, will catalyze both the forward and back reaction on both arms of the coumermycin scaffold. This occurs via an O-acyl-Ser101-CouN7 intermediate, as shown by transient labeling of the enzyme with [14C]acetyl-S-CouN1 as donor and by inactivating mutation of the active site, Ser101, to Ala. The intermediacy of the pyrrolyl-2-carbonyl-O-CouN7 allows net pyrrole transfer between distinct aminocoumarin scaffolds, for example, between the descarbamoylnovobiocin scaffold and coumermycin A1 and vice versa. CouN7 also allows shuttling of surrogate acyl groups between noviosyl-aminocoumarin scaffolds to generate new antibiotic variants.

Original languageEnglish
Pages (from-to)679-690
Number of pages12
JournalChemistry and Biology
Issue number6
StatePublished - Jun 25 2007

Bibliographical note

Funding Information:
We thank Dr. Micha Fridman for the gift of 5-methylthiophene-CoA and Dr. Danica Galonic for a careful reading of the manuscript. Supported in part by National Institutes of Health grant GM 20011 (C.T.W.) and a Department of Defense National Defense Science and Engineering Graduate Fellowship (C.J.B.).



ASJC Scopus subject areas

  • Biochemistry
  • Molecular Medicine
  • Molecular Biology
  • Pharmacology
  • Drug Discovery
  • Clinical Biochemistry


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