title: A vitamin B₁₂ transporter in Mycobacterium tuberculosis.
abstract: Vitamin B₁₂-dependent enzymes function in core biochemical pathways in Mycobacterium tuberculosis, an obligate pathogen whose metabolism in vivo is poorly understood. Although M. tuberculosis can access vitamin B₁₂ in vitro, it is uncertain whether the organism is able to scavenge B₁₂ during host infection. This question is crucial to predictions of metabolic function, but its resolution is complicated by the absence in the M. tuberculosis genome of a direct homologue of BtuFCD, the only bacterial B₁₂ transport system described to date. We applied genome-wide transposon mutagenesis to identify M. tuberculosis mutants defective in their ability to use exogenous B₁₂. A small proportion of these mapped to Rv1314c, identifying the putative PduO-type ATP : co(I)rrinoid adenosyltransferase as essential for B₁₂ assimilation. Most notably, however, insertions in Rv1819c dominated the mutant pool, revealing an unexpected function in B₁₂ acquisition for an ATP-binding cassette (ABC)-type protein previously investigated as the mycobacterial BacA homologue. Moreover, targeted deletion of Rv1819c eliminated the ability of M. tuberculosis to transport B₁₂ and related corrinoids in vitro. Our results establish an alternative to the canonical BtuCD-type system for B₁₂ uptake in M. tuberculosis, and elucidate a role in B₁₂ metabolism for an ABC protein implicated in chronic mycobacterial infection.
authors: MRC/NHLS/UCT Molecular Mycobacteriology Research Unit and DST/NRF Centre of Excellence for Biomedical Tuberculosis Research, University of Cape Town, Observatory, Cape Town 7925, South Africa.
authors: Krishnamoorthy
authors: K
authors: Gopinath
authors: Ceslovas
authors: C
authors: Venclovas
authors: Thomas R
authors: TR
authors: Ioerger
authors: James C
authors: JC
authors: Sacchettini
authors: John D
authors: JD
authors: McKinney
authors: Valerie
authors: V
authors: Mizrahi
authors: Digby F
authors: DF
authors: Warner
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D004251:DNA Transposable Elements / Q000235:genetics; D016680:Genome, Bacterial / Q000187:drug effects; D054884:Host-Pathogen Interactions / Q000235:genetics*; D006801:Humans; D016296:Mutagenesis; D009154:Mutation; D009164:Mycobacterium Infections / Q000378:metabolism / Q000382:microbiology; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D014805:Vitamin B 12 / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D018528:ATP-Binding Cassette Transporters; D004251:DNA Transposable Elements; D014805:Vitamin B 12