Acta Crystallographica Section D

Biological Crystallography

Volume 69, Part 8 (August 2013)

research papers

Acta Cryst. (2013). D69, 1403-1413    [ doi:10.1107/S0907444913008354 ]

Trapped intermediates in crystals of the FMN-dependent oxidase PhzG provide insight into the final steps of phenazine biosynthesis

N. Xu, E. G. Ahuja, P. Janning, D. V. Mavrodi, L. S. Thomashow and W. Blankenfeldt

Abstract: Phenazines are redox-active secondary metabolites that many bacteria produce and secrete into the environment. They are broad-specificity antibiotics, but also act as virulence and survival factors in infectious diseases. Phenazines are derived from chorismic acid, but important details of their biosynthesis are still unclear. For example, three two-electron oxidations seem to be necessary in the final steps of the pathway, while only one oxidase, the FMN-dependent PhzG, is conserved in the phenazine-biosynthesis phz operon. Here, crystal structures of PhzG from Pseudomonas fluorescens 2-79 and from Burkholderia lata 383 in complex with excess FMN and with the phenazine-biosynthesis intermediates hexahydrophen­azine-1,6-dicarboxylate and tetrahydrophenazine-1-carboxyl­ate generated in situ are reported. Corroborated with biochemical data, these complexes demonstrate that PhzG is the terminal enzyme in phenazine biosynthesis and that its relaxed substrate specificity lets it participate in the generation of both phenazine-1,6-dicarboxylic acid (PDC) and phen­azine-1-carboxylic acid (PCA). This suggests that competition between flavin-dependent oxidations through PhzG and spontaneous oxidative decarboxylations determines the ratio of PDC, PCA and unsubstituted phenazine as the products of phenazine biosynthesis. Further, the results indicate that PhzG synthesizes phenazines in their reduced form. These reduced molecules, and not the fully aromatized derivatives, are the likely end products in vivo, explaining why only one oxidase is required in the phenazine-biosynthesis pathway.

PDB references: 4hms, 4hmt, 4hmu, 4hmw, 4hmx and 4hmv

Keywords: antibiotics; hydride transfer; reaction mechanism; flavins; PdxH.

pdfdisplay filedownload file

Portable Document Format (PDF) file (775.3 kbytes)
[ doi:10.1107/S0907444913008354/cb5027sup1.pdf ]
Supplementary Material.


To open or display or play some files, you may need to set your browser up to use the appropriate software. See the full list of file types for an explanation of the different file types and their related mime types and, where available links to sites from where the appropriate software may be obtained.

The download button will force most browsers to prompt for a file name to store the data on your hard disk.

Where possible, images are represented by thumbnails.

 bibliographic record in  format

  Find reference:   Volume   Page   
  Search:     From   to      Advanced search

Copyright © International Union of Crystallography
IUCr Webmaster