Bioactivity-guided mass spectral net working reveals a new set of allbicidin derivatives from Xanthomonas albilineans

Dang Tam, Petras Daniel, Pesic Alexander, Cociancich Stéphane, Royer Monique, Dorrestein Pieter C., Süssmuth Roderich. 2016. Bioactivity-guided mass spectral net working reveals a new set of allbicidin derivatives from Xanthomonas albilineans. Journal of Peptide Science, 22, n.spéc. S2 : S159-S160. European Peptide Symposium, Leipzig, Allemagne, 4 September 2016/9 September 2016.

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Abstract : Albicidin is produced by the sugarcane pathogenic bacterium Xanthomonas albilineans and is a potent antibiotic specifically targeting the bacterial DNA gyrase with an IC50 value in the nanomolar range. The structure of albicidin, which has remained unsolved for more than three decades since its first description, has been solved by a combination of extensive NMR and HR-MS/MS experiments. An inherent problem for the structure elucidation was the low amount of the albicidin production in cell culture. The low production forced us to cultivate several hundred liters in order to purify a few milligrams required for NMR experiments. In comparison, LC-HR-MS/MS has the great advantage of several orders of magnitude and high sensitivity. Thus, this approach requires much less material. But more importantly, purification of compounds is not necessary for structural analysis. Due to the application of targeted LC-MS/MS experiments, we were able to propose the structure of N-terminal carba- S158 moylated and b-methoxylated albicidin derivatives. Both of them are currently chemically synthesized and studied in a medicinal chemistry campaign. In order to search for more pharmaceutically relevant albicidin derivatives, we applied non-targeted LC-HR-MS/MS approaches combined with mass spectral networking, a recently introduced approach for non-targeted MS/MS data-analysis. However, as for the structural elucidation of albicidin, the even lower concentrated derivatives resulted in difficulties to obtain useful MS/ MS spectra. Since we typically operate the mass spectrometer in data-dependent acquisition mode (DDA), it inherently selects high abundant compounds of cell extracts for MS/ MS scans and possibly ignore low abundant compounds. The same goes for the network analysis which is based on similarity of MS/MS spectra and may not take potential ion species into account. To overcome this problem, we implemented a bioactivity-guided fractionation by solid phase extraction and semi-preparative HPLC. Fractions with antibacterial activity were subsequently submitted to several LC-MS/MS runs in DDA mode with shifted survey scan windows (stitched DDA). Besides the increased amount of MS/MS events per mass range, narrowing down the m/z range of the survey scan also increased the dynamic range of the orbitrap analyzer, which enabled us to significantly increase the method's sensitivity. Finally, we were able to detect a whole series of new albicidin derivatives and to propose their structures based on exact mass determination and MS/MS fragmentation patterns. These new compounds provide great opportunities in lead optimization of albicidin as a new anti-infective drug. Apart from the pharmaceutical relevance, some of the identified by-products give us important insights into the formation of albicidin and its intriguing biosynthetic machinery. (Résumé d'auteur)

Mots-clés Agrovoc : Phytotoxine, Antibiotique, Xanthomonas albilineans, Saccharum officinarum, Métabolite secondaire, Structure chimique, Biosynthèse, Utilisation

Mots-clés complémentaires : Albicidine

Classification Agris : H20 - Plant diseases
000 - Autres thèmes
L73 - Animal diseases

Champ stratégique Cirad : Axe 4 (2014-2018) - Santé des animaux et des plantes

Auteurs et affiliations

  • Dang Tam, Technische Universitaet Berlin (DEU)
  • Petras Daniel, Technische Universitaet Berlin (DEU)
  • Pesic Alexander, Technische Universitaet Berlin (DEU)
  • Cociancich Stéphane, CIRAD-BIOS-UMR BGPI (FRA)
  • Royer Monique, CIRAD-BIOS-UMR BGPI (FRA)
  • Dorrestein Pieter C., Skaggs School of Pharmacy and Pharmaceutical Sciences (USA)
  • Süssmuth Roderich, Technische Universitaet Berlin (DEU)

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