Discovery of a Cryptic Intermediate in Late Steps of Mithramycin Biosynthesis

Ryan Wheeler, Xia Yu, Caixia Hou, Prithiba Mitra, Jhong Min Chen, Frank Herkules, Dmitri N. Ivanov, Oleg V. Tsodikov, Jürgen Rohr

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


MtmOIV and MtmW catalyze the final two reactions in the mithramycin (MTM) biosynthetic pathway, the Baeyer–Villiger opening of the fourth ring of premithramycin B (PMB), creating the C3 pentyl side chain, strictly followed by reduction of the distal keto group on the new side chain. Unexpectedly this results in a C2 stereoisomer of mithramycin, iso-mithramycin (iso-MTM). Iso-MTM undergoes a non-enzymatic isomerization to MTM catalyzed by Mg2+ ions. Crystal structures of MtmW and its complexes with co-substrate NADPH and PEG, suggest a catalytic mechanism of MtmW. The structures also show that a tetrameric assembly of this enzyme strikingly resembles the ring-shaped β subunit of a vertebrate ion channel. We show that MtmW and MtmOIV form a complex in the presence of PMB and NADPH, presumably to hand over the unstable MtmOIV product to MtmW, yielding iso-MTM, as a potential self-resistance mechanism against MTM toxicity.

Original languageEnglish
Pages (from-to)826-832
Number of pages7
JournalAngewandte Chemie - International Edition
Issue number2
StatePublished - Jan 7 2020

Bibliographical note

Funding Information:
The work was supported by NIH grants CA 091901 and GM 1051977 to J.R. Dr. Joe Eckenrode and Dr. Markos Leggas are acknowledged for the anti-cancer activity assays of iso-MTM. We also thank the University of Kentucky (UK), College of Pharmacy PharmNMR Center for their assistance with NMR data collection, the staff of sector SER-CAT at the Advanced Photon Source for assistance with remote data X-ray diffraction data collection and the Center for Structural Biology at the UK for funding support of the synchrotron beamline.

Publisher Copyright:
© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim


  • biocatalysis
  • biosynthesis
  • isomerization
  • natural products
  • protein structures

ASJC Scopus subject areas

  • Catalysis
  • Chemistry (all)


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