title: HemZ is essential for heme biosynthesis in Mycobacterium tuberculosis.
abstract: The complete sequence and subsequent annotation of the Mycobacterium tuberculosis genome has allowed the prediction of many genes and gene functions by homology. HemZ is a predicted ferrochelatase which lies in an apparent operon with two genes involved in mycolic acid biosynthesis, mabA and inhA. We tried to construct hemZ deletion mutants in M. tuberculosis using a two-step recombination strategy, but could only delete the chromosomal copy when we provided a second functional copy on an integrating plasmid. We further confirmed that hemZ is essential under normal culture conditions by demonstrating that the integrated copy of hemZ could not be removed if it was the only wild-type allele in the cell. We were able to obtain hemZ mutants by supplementation with hemin but not with protoporphyrin IX or hemoglobin confirming that this gene does have a role in heme biosynthesis and that M. tuberculosis can transport hemin intracelullarly. The hemin auxotroph required 2 mug/ml hemin for growth and rapid loss of viability occurred after withdrawal of hemin. These data confirm the role of hemZ in heme biosynthesis and indicate that heme is an essential requirement for M. tuberculosis.
authors.affiliation: Centre for Infectious Disease, Institute of Cell and Molecular Science, Barts and the London, Queen Mary's School of Medicine and Dentistry, Turner Street, London E1 2AD, UK. t.parish@qmul.ac.uk
authors.forename: Tanya
authors.initials: T
authors.lastname: Parish
authors.forename: Merrill
authors.initials: M
authors.lastname: Schaeffer
authors.forename: Gretta
authors.initials: G
authors.lastname: Roberts
authors.forename: Ken
authors.initials: K
authors.lastname: Duncan
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D004254:DNA Nucleotidyltransferases; D017353:Gene Deletion; D005798:Genes, Bacterial; D005822:Genetic Vectors; D023281:Genomics; D006418:Heme / Q000096:biosynthesis*; D006427:Hemin / Q000494:pharmacology; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics; D011995:Recombination, Genetic; D014764:Viral Proteins
chemical_list: D001426:Bacterial Proteins; C121787:HemZ protein, Bacteria; D014764:Viral Proteins; D006418:Heme; D006427:Hemin; D004254:DNA Nucleotidyltransferases; C063911:excisionase