A Francisella virulence factor catalyses an essential reaction of biotin synthesis

• Type of Material: Article
• Authors: Youjun Feng, University of Illinois; Brooke A. Napier, Emory University; Miglena Manandhar, University of Illinois; Sarah K Henke, University of Illinois; David S Weiss, Emory University; John E. Cronan, University of Illinois
• Language: English
• Date: 2014-01-01
• Publisher: Wiley: 12 months
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2013 John Wiley & Sons Ltd.
• Final Published Version (URL): http://dx.doi.org/10.1111/mmi.12460
• Title of Journal or Parent Work: Molecular Microbiology
• ISSN: 0950-382X
• Volume: 91
• Issue: 2
• Start Page: 300
• End Page: 314
• Grant/Funding Information: D.S.W. was supported by NIH/NIAID grant U54-AI057157 from the Southeastern Regional Center of Excellence for Emerging Infections; and Biodefense and a Burroughs Wellcome Fund Investigator in the Pathogenesis of Infectious Disease award.; This work was supported by National Institutes of Health (NIH) grant AI15650 to J.E.C.; from National Institute of Allergy and Infectious Diseases (NIAID).
• Keywords: COMPLETE GENOME SEQUENCE; RECEPTORS; BINDING; Microbiology; Science & Technology; ACYL CARRIER PROTEIN; REPRESSOR; PROLIFERATION; TULARENSIS; Biochemistry & Molecular Biology; Life Sciences & Biomedicine; RECOGNITION; MECHANISMS; PHAGOSOMAL ESCAPE
• Research Categories: Biology, Microbiology; Chemistry, Biochemistry

Abstract

We recently identified a gene (FTN_0818) required for Francisella virulence that seemed likely involved in biotin metabolism. However, the molecular function of this virulence determinant was unclear. Here we show that this protein named BioJ is the enzyme of the biotin biosynthesis pathway that determines the chain length of the biotin valeryl side-chain. Expression of bioJ allows growth of an Escherichia colibioH strain on biotin-free medium, indicating functional equivalence of BioJ to the paradigm pimeloyl-ACP methyl ester carboxyl-esterase, BioH. BioJ was purified to homogeneity, shown to be monomeric and capable of hydrolysis of its physiological substrate methyl pimeloyl-ACP to pimeloyl-ACP, the precursor required to begin formation of the fused heterocyclic rings of biotin. Phylogenetic analyses confirmed that distinct from BioH, BioJ represents a novel subclade of the α/β-hydrolase family. Structure-guided mapping combined with site-directed mutagenesis revealed that the BioJ catalytic triad consists of Ser151, Asp248 and His278, all of which are essential for activity and virulence. The biotin synthesis pathway was reconstituted reaction in vitro and the physiological role of BioJ directly assayed. To the best of our knowledge, these data represent further evidence linking biotin synthesis to bacterial virulence.