Location: Plant Genetics ResearchTitle: In silico biosynthesis of virenose, a methylated deoxy-sugar unique to Coxiella burnetii lipopolysaccharide Author
Submitted to: Proteome Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2012
Publication Date: 11/15/2012
Publication URL: http://handle.nal.usda.gov/10113/56842
Citation: Flores-Ramirez, G., Janecek, S., Miernyk, J.A., Skultety, L. 2012. In silico biosynthesis of virenose, a methylated deoxy-sugar unique to Coxiella burnetii lipopolysaccharide. Proteome Science. 10:67. Interpretive Summary: The manuscript describes a novel approach for predicted metabolic pathways for the generation of specific compounds in a biological system. The coat surrounding the bacterium Coxiella burnetii contains a unique sugar that has been assigned the trivial name virenose. This sugar is thought to be important for identification of the bacteria, and for development of therapeutic agents. The pathway for production of this sugar is unknown. Based on results from analysis of the genome and the proteome, a hypothetical pathway for production was predicted. The pathway includes five steps. The predictions will serve as a scaffold for the design of future biological experiments to directly test the pathway. Definition of the pathway will facilitate the development of therapeutic agents useful for treatment of infection by this bacterium, as well as allowing improvements in the methods for diagnosis. Although this study is specifically aimed at a bacterial pathway it served as a model for the application of this approach to much broader applications and more complex systems. The success of this model, as documented in this report, allows us to move forward to uncover pathway architecture in seed metabolism for soybean improvement strategies.
Technical Abstract: Background: Coxiella burnetii is Gram-negative bacterium responsible for the zoonosis Q-fever. While it has an obligate intracellulargrowth habit, it is able to persist for extended periods outside of a host cell and can resist environmental conditions that would be lethal to most prokaryotes. It is these extracellular bacteria that are the infectious stage encountered by eukaryotic hosts. The intracellular form has evolved to grow and replicate within acidified parasitophorous vacuoles. The outer coat of C. burnetii comprises a complex lipopolysaccharide (LPS) component that includes the unique methylated-6-deoxyhexose, virenose. Although potentially important as a biomarker for C. burnetii, the pathway for its biosynthesis remains obscure. Results: The 6-deoxyhexoses constitute a large family integral to the LPS of many eubacteria. It is believed that precursors of the methylated-deoxyhexoses traverse common early biosynthetic steps as nucleotide-monosaccharides. As a prelude to a full biosynthetic characterization, we present herein the results from bioinformatics-based, proteomics-supported predictions of the pathway for virenose synthesis. Alternative possibilities are considered which include both GDP-mannose and TDP-glucose as precursors. Conclusion: We propose that biosynthesis of the unique C. burnetii biomarker, virenose, involves an early pathway similar to that of other C-3’-methylated deoxysugars which then diverges depending upon the nucleotide-carrier involved. The alternatives yield either the D- or L-enantiomers of virenose. Both pathways require five enzymatic steps, beginning with either glucose-6-phosphate or mannose-6-phosphate. Our in silico results comprise a model for virenose biosynthesis that can be directly tested. Definition of this pathway should facilitate the development of therapeutic agents useful for treatment of Q fever, as well as allowing improvements in the methods for diagnosing this highly infectious disease.