title: Pseudomonas aeruginosa D-arabinofuranose biosynthetic pathway and its role in type IV pilus assembly.
abstract: Pseudomonas aeruginosa strains PA7 and Pa5196 glycosylate their type IVa pilins with α1,5-linked D-arabinofuranose (d-Araf), a rare sugar configuration identical to that found in cell wall polymers of the Corynebacterineae. Despite this chemical identity, the pathway for biosynthesis of α1,5-D-Araf in Gram-negative bacteria is unknown. Bioinformatics analyses pointed to a cluster of seven P. aeruginosa genes, including homologues of the Mycobacterium tuberculosis genes Rv3806c, Rv3790, and Rv3791, required for synthesis of a polyprenyl-linked d-ribose precursor and its epimerization to D-Araf. Pa5196 mutants lacking the orthologues of those genes had non-arabinosylated pilins, poor twitching motility, and significantly fewer surface pili than the wild type even in a retraction-deficient (pilT) background. The Pa5196 pilus system assembled heterologous non-glycosylated pilins efficiently, demonstrating that it does not require post-translationally modified subunits. Together the data suggest that pilins of group IV strains need to be glycosylated for productive subunit-subunit interactions. A recombinant P. aeruginosa PAO1 strain co-expressing the genes for d-Araf biosynthesis, the pilin modification enzyme TfpW, and the acceptor PilA(IV) produced arabinosylated pili, confirming that the Pa5196 genes identified are both necessary and sufficient. A P. aeruginosa epimerase knock-out could be complemented with the corresponding Mycobacterium smegmatis gene, demonstrating conservation between the systems of the Corynebacterineae and Pseudomonas. This work describes a novel Gram-negative pathway for biosynthesis of d-Araf, a key therapeutic target in Corynebacterineae.
authors.affiliation: Michael G DeGroote Institute for Infectious Diseases Research and the Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8N 3Z5, Canada.
authors.forename: Hanjeong
authors.initials: H
authors.lastname: Harvey
authors.forename: Julianne V
authors.initials: JV
authors.lastname: Kus
authors.forename: Luc
authors.initials: L
authors.lastname: Tessier
authors.forename: John
authors.initials: J
authors.lastname: Kelly
authors.forename: Lori L
authors.initials: LL
authors.lastname: Burrows
mesh_terms: D001089:Arabinose / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000235:genetics; D002238:Carbohydrate Epimerases / Q000235:genetics / Q000378:metabolism*; D036781:Fimbriae Proteins / Q000235:genetics / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism*
chemical_list: C431714:arabinofuranose; D036781:Fimbriae Proteins; D001089:Arabinose; D002238:Carbohydrate Epimerases