An unusual Burkholderia gladioli double chain-initiating nonribosomal peptide synthetase assembles ‘fungal’ icosalide antibiotics

Matthew Jenner; Xinyun Jian; Yousef Dashti; Joleen Masschelein; Christian Hobson; Douglas M. Roberts; Cerith Jones; Simon Harris; Julian Parkhill; Huzefa A. Raja; Nicholas H. Oberlies; Cedric J. Pearce; Eshwar Mahenthiralingam; Gregory L. Challis

doi:10.1039/C8SC04897E

An unusual Burkholderia gladioli double chain-initiating nonribosomal peptide synthetase assembles ‘fungal’ icosalide antibiotics†

Matthew Jenner,

‡^ab Xinyun Jian,‡^a Yousef Dashti,

^a Joleen Masschelein,

^a Christian Hobson,^a Douglas M. Roberts,^a Cerith Jones,

^d Simon Harris,

^e Julian Parkhill,

^e Huzefa A. Raja,

^f Nicholas H. Oberlies,

^f Cedric J. Pearce,^g Eshwar Mahenthiralingam

^d and Gregory L. Challis

*^abc

Author affiliations

* Corresponding authors

^a Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK
E-mail: g.l.challis@warwick.ac.uk

^b Warwick Integrative Synthetic Biology Centre, University of Warwick, Coventry CV4 7AL, UK

^c Biomedicine Discovery Institute, Department of Biochemistry and Molecular Biology, Monash University, Victoria 3800, Australia

^d Organisms and Environment Division, Cardiff School of Biosciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK

^e Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK

^f Department of Chemistry and Biochemistry, University, of North Carolina at Greensboro, Greensboro, NC 27402, USA

^g Mycosynthetix, 4905 Pine Cone Drive, Durham, North Carolina, USA

Abstract

Burkholderia is a multi-talented genus of Gram-negative bacteria, which in recent years has become increasingly recognised as a promising source of bioactive natural products. Metabolite profiling of Burkholderia gladioli BCC0238 showed that it produces the asymmetric lipopeptidiolide antibiotic icosalide A1, originally isolated from a fungus. Comparative bioinformatics analysis of several genome-sequenced B. gladioli isolates identified a gene encoding a nonribosomal peptide synthase (NRPS) with an unusual architecture that was predicted to be responsible for icosalide biosynthesis. Inactivation of this gene in B. gladioli BCC0238 abolished icosalide production. PCR analysis and sequencing of total DNA from the original fungal icosalide A1 producer revealed it has a B. gladioli strain associated with it that harbours an NRPS with an identical architecture to that responsible for icosalide A1 assembly in B. gladioli BCC0238. Sequence analysis of the icosalide NRPS indicated that it contains two chain-initiating condensation (C_I) domains. One of these is appended to the N-terminus of module 1 – a common architecture for NRPSs involved in lipopeptide assembly. The other is embedded in module 3, immediately downstream of a putative chain-elongating condensation domain. Analysis of the reactions catalysed by a tridomain construct from module 3 of the NRPS using intact protein mass spectrometry showed that the embedded C_I domain initiates assembly of a second lipopeptide chain, providing key insights into the mechanism for asymmetric diolide assembly.

Chemical Science

An unusual Burkholderia gladioli double chain-initiating nonribosomal peptide synthetase assembles ‘fungal’ icosalide antibiotics†

Abstract

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An unusual Burkholderia gladioli double chain-initiating nonribosomal peptide synthetase assembles ‘fungal’ icosalide antibiotics

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