Characterization of the Polymyxin D Synthetase Biosynthetic Cluster and Product Profile of Paenibacillus polymyxa ATCC 10401

The increasing prevalence of polymyxin-resistant bacteria has stimulated the search for improved polymyxin lipopeptides. Here we describe the sequence and product profile for polymyxin D nonribosomal peptide synthetase from Paenibacillus polymyxa ATCC 10401. The polymyxin D synthase gene cluster com...

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Bibliographic Details
Published in:Journal of natural products (Washington, D.C.) D.C.), 2017-05, Vol.80 (5), p.1264-1274
Main Authors: Galea, Charles A, Han, Meiling, Zhu, Yan, Roberts, Kade, Wang, Jiping, Thompson, Philip E, L, Jian, Velkov, Tony
Format: Article
Language:English
Subjects:
Animals
Anti-Bacterial Agents - chemistry
Anti-Bacterial Agents - pharmacology
Ligases - biosynthesis
Ligases - chemistry
Ligases - metabolism
Lipopeptides - chemistry
Lipopeptides - metabolism
Mice
Molecular Structure
Multigene Family
Paenibacillus polymyxa - chemistry
Polymyxins - biosynthesis
Polymyxins - chemistry
Polymyxins - metabolism
Polymyxins - pharmacology
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Summary:The increasing prevalence of polymyxin-resistant bacteria has stimulated the search for improved polymyxin lipopeptides. Here we describe the sequence and product profile for polymyxin D nonribosomal peptide synthetase from Paenibacillus polymyxa ATCC 10401. The polymyxin D synthase gene cluster comprised five genes that encoded ABC transporters (pmxC and pmxD) and enzymes responsible for the biosynthesis of polymyxin D (pmxA, pmxB, and pmxE). Unlike polymyxins B and E, polymyxin D contains d-Ser at position 3 as opposed to l-α,γ-diaminobutyric acid and has an l-Thr at position 7 rather than l-Leu. Module 3 of pmxE harbored an auxiliary epimerization domain that catalyzes the conversion of l-Ser to the d-form. Structural modeling suggested that the adenylation domains of module 3 in PmxE and modules 6 and 7 in PmxA could bind amino acids with larger side chains than their preferred substrate. Feeding individual amino acids into the culture media not only affected production of polymyxins D1 and D2 but also led to the incorporation of different amino acids at positions 3, 6, and 7 of polymyxin D. Interestingly, the unnatural polymyxin analogues did not show antibiotic activity against a panel of Gram-negative clinical isolates, while the natural polymyxins D1 and D2 exhibited excellent in vitro antibacterial activity and were efficacious against Klebsiella pneumoniae and Acinetobacter baumannii in a mouse blood infection model. The results demonstrate the excellent antibacterial activity of these unusual d-Ser3 polymxyins and underscore the possibility of incorporating alternate amino acids at positions 3, 6, and 7 of polymyxin D via manipulation of the polymyxin nonribosomal biosynthetic machinery.
ISSN:0163-3864
1520-6025
DOI:10.1021/acs.jnatprod.6b00807