Isolation and structure elucidation of lipopeptide antibiotic taromycin B from the activated taromycin biosynthetic gene cluster

Abstract

In the ongoing effort to unlock the chemical potential of marine bacteria, genetic engineering of biosynthetic gene clusters (BGCs) is increasingly used to awake or improve expression of biosynthetic genes that may lead to discovery of novel bioactive natural products. Previously, we reported the successful capture, engineering and heterologous expression of an orphan BGC from the marine actinomycete Saccharomonospora sp. CNQ-490, which resulted in the isolation of the novel lipopeptide antibiotic taromycin A. Herein we report the isolation and structure elucidation of taromycin B, the second most abundant product of the taromycin biosynthetic series, and show that taromycins A and B exhibit complex chromatographic properties indicative of interconverting conformations. Taromycins A and B display potent activity against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecium clinical isolates, suggestive that the taromycin molecular scaffold is a promising starting point for further derivatization to produce compounds with promising antibiotic characteristics.

A Versatile Boc Solid Phase Synthesis of Daptomycin and Analogues Using Site Specific, On‐Resin Ozonolysis to Install the Kynurenine Residue

“…The preference to use Fmoc SPPS over Boc SPPS is largely due to the need to use hazardous HF,b ut HF-free Boc SPPS protocols have been reported [29] which should aid in preparing difficult peptides equences such as daptomycin.T his approacho pens the door for the rapid preparation of various daptomycin analogues to establish SARs, andm ay be useful for the synthesis of other cyclic lipodepsipeptide naturalp roductsc ontaining aK yn residue such as taromycin Aa nd B. [30] Through biological evaluation of our daptomycin compounds, we have determined that the stereochemistry of the a-carbon and the 3-substitutedm ethyl group in the MeGlu 12 residue of daptomycin (1)m ust be (2S,3R)t o confer activity.T he preparation of other daptomycin analogues to furthere xplore the SAR is currently being carriedo ut and will be reportedi nd ue course. > 128 dapt-lys 6 /glu 12 18 64 dapt-kyn 1 /glu 12 19 > 128 dapt-kyn 1 /lys 6 /glu 12 20 > 128…”

Biosynthesis of l‐4‐Chlorokynurenine, an Antidepressant Prodrug and a Non‐Proteinogenic Amino Acid Found in Lipopeptide Antibiotics

“…Biologically, 1 was recently identified as an amino acid building block in the lipopeptide antibiotics taromycin A ( 2 ) and B ( 3 ; Figure A) and in the putative glycopeptide antibiotic complex INA‐5812 . With the concurrent discovery of the taromycin biosynthetic gene cluster (BGC) from the marine actinomycete Saccharomonospora sp.…”

“…[3] To date,only synthetic routes to 1 have been described. [3,4] Biologically, 1 was recently identified as an amino acid building block in the lipopeptide antibiotics taromycin A(2) and B( 3;F igure 1A) [5,6] and in the putative glycopeptide antibiotic complex INA-5812. [7] With the concurrent discovery of the taromycin biosynthetic gene cluster (BGC) from the marine actinomycete Saccharomonospora sp.C NQ-490, we sought to establish the biosynthetic logic for the bacterial synthesis of l-4-Cl-Kyn.…”

Marine Proteobacteria as a source of natural products: advances in molecular tools and strategies

“…17,[69][70][71] There are several advantages in developing such genetic manipulation tools. First, gene-targeting mutagenesis could link orphan BGCs to identified bioactive compounds, 72,73 which is the foundation and prerequisite for refactoring BGCs in either the native producers or the surrogate hosts. In addition, the native producers encode all structural genes and regulatory elements for the expression of BGCs, such as promoters, genetic regulators, and host cell self-protection genes.…”