Decorating with Amino Acids: Biosynthetic Investigation of a Unique Polyphenol Antibiotic

As bacteria become increasingly resistant to current antibiotics, the need for research to create new antibiotics is crucial. The natural antibiotic molecule TLN‐05220 is biosynthesized by Micromonospora echinospora ssp. challisensis NRRL 12255 and exhibits bioactivity against antibiotic‐resistant bacteria in the same range as vancomycin. It is a hexacyclic aromatic polyketide that also contains a unique nitrogen‐containing piperazinone ring, which is found in only a few other natural products. The original report of TLN‐05220 includes a draft genome sequence of the producing strain, and a potential gene cluster for construction of the polyphenol core. It is also hypothesized that a non‐ribosomal peptide synthase (NRPS) is responsible for the production of the piperazinone ring. Here we propose an alternate M. echinospora strain that produces TLN‐05220 as demonstrated through investigation of its genome and mass spectrometry analysis of its secondary metabolites. Through bioinformatic analysis of this strain's genome, we found a strikingly similar biosynthetic gene cluster for production of a hexacyclic polyphenol to that proposed in the original report. However, there are no NRPS genes within or nearby this cluster. Instead, we have identified two asparagine synthetases that lack a highly conserved N ‐terminal cysteine residue ‐– suggesting instead that they act as amino acid ligases, incorporating an entire amino acid entity instead of the transfer of a nitrogen atom. Therefore, we hypothesize that alanine, glycine, and diaminoproprionic acid are incorporated into the structure by these amino acid ligases and other tailoring enzymes. We will confirm their incorporation by feeding 13 C‐labeled amino acids to cultures of M. echinospora on semi‐solid agar plates and analyzing the culture by Matrix Assisted Laser Desorption Ionization (MALDI) Mass Spectrometry. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .