Functional characterization of O-methyltransferases used to catalyse site-specific methylation in the post-tailoring steps of pradimicin biosynthesis

J. W. Han, B. G. Ng, J. K. Sohng, Y. J. Yoon, G. J. Choi, Beom Seok Kim

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Aims: To identify the roles of the two O-methyltransferase homologous genes pdmF and pdmT in the pradimicin biosynthetic gene cluster of Actinomadura hibisca P157-2. Methods and Results: Pradimicins are pentangular polyphenol antibiotics synthesized by bacterial type II polyketide synthases (PKSs) and tailoring enzymes. Pradimicins are naturally derivatized by combinatorial O-methylation at two positions (i.e., 7-OH and 11-OH) of the benzo[α]naphthacenequinone structure. PdmF and PdmT null mutants (PFKO and PTKO) were generated. PFKO produced the 11-O-demethyl shunt metabolites 11-O-demethylpradimicinone II (1), 11-O-demethyl-7-methoxypradimicinone II (2), 11-O-demethylpradimicinone I (3) and 11-O-demethylpradimicin A (4), while PTKO generated the 7-O-demethyl derivatives pradimicinone II (5) and 7-hydroxypradimicin A (6). Pradimicinones 1, 2, 3, and 5 were fed to a heterologous host Escherichia coli harbouring expression plasmid pET-22b::pdmF or pET-28a::pdmT. PdmF catalysed 11-O-methylation of pradimicinones 1, 2, and 3 regardless of O-methylation at the C-7 position, while PdmT was unable to catalyse 7-O-methylation when the C-11 hydroxyl group was methylated (5). Conclusions: PdmF and PdmT were involved in 11-O- and 7-O-methylations of the benzo[α]naphthacenequinone moiety of pradimicin, respectively. Methylation of the C-7 hydroxyl group precedes methylation of the C-11 hydroxyl group in pradimicin biosynthesis. Significance and Impact of the Study: This is the first reported demonstration of the functions of PdmF and PdmT for regiospecific O-methylation, which contributes to better understanding of the post-PKS modifications in pradimicin biosynthesis as well as to rational engineering of the pradimicin biosynthetic machinery.

Original languageEnglish
Pages (from-to)144-154
Number of pages11
JournalJournal of Applied Microbiology
Volume124
Issue number1
DOIs
Publication statusPublished - 2018 Jan 1

Keywords

  • aromatic polyketide
  • methyltransferase
  • O-methyltransferase
  • polyketide
  • pradimicin
  • pradimicin biosynthesis
  • pradimicinone

ASJC Scopus subject areas

  • Biotechnology
  • Applied Microbiology and Biotechnology

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