Discovery and characterization of a unique mycobacterial heme acquisition system

Abstract

Mycobacterium tuberculosis must import iron from its host for survival, and its siderophore-dependent iron acquisition pathways are well established. Here we demonstrate a newly characterized pathway, whereby M. tuberculosis can use free heme and heme from hemoglobin as an iron source. Significantly, we identified the genomic region, Rv0202c – Rv0207c , responsible for the passage of heme iron across the mycobacterial membrane. Key players of this heme uptake system were characterized including a secreted protein and two transmembrane proteins, all three specific to mycobacteria. Furthermore, the crystal structure of the key heme carrier protein Rv0203 was found to have a unique fold. The discovery of a unique mycobacterial heme acquisition pathway opens new avenues of exploration into mycobacterial therapeutics.

Self-poisoning of Mycobacterium tuberculosis by interrupting siderophore recycling

“…S1]. One possible explanation is that Mtb cannot use iron salts without siderophores, as observed previously with some siderophore biosynthesis mutants (15,16) but not with others (17). Even 100 mM ferric citrate failed to stimulate the growth of Mtb siderophore biosynthesis mutant ΔmbtD::hyg, whereas the Mycobacterium smegmatis siderophore biosynthesis mutant ΔfxbA::hygΔmbtD::kan (18) was rescued by 50 μM ferric citrate (SI Appendix, Fig.…”

Characterization of a Mycobacterium tuberculosis Nanocompartment and Its Potential Cargo Proteins

“…To generate the Mtb⌬mbtB⌬mhuD mutant, we constructed an allelic exchange substrate by cloning a 1.9-kb PCR product, including the entire mhuD gene and flanking regions, and then replacing 222 nucleotides of the mhuD gene (encoding amino acids 10 -85 of the 105-amino acid MhuD protein) with an apramycin resistance cassette, using essentially the same strategy described previously for construction of Mtb⌬mbtB⌬mmpL11 and Mtb⌬mbtB⌬Rv0203 (20). To generate the ⌬dyP mutants, Mtb⌬mbtB⌬dyP and Mtb⌬mbtB⌬mhuD⌬dyP, we first inserted an 849-nucleotide in-frame, unmarked deletion of dyP (encoding amino acids 21-303 of the 335-amino acid DyP protein) flanked by a hygromycin resistance gene and sacB cassette (hygsacB) into the dyP region of the chromosome by specialized transduction.…”

“…Mtb⌬mbtB, a mycobactin-deficient mutant of M. tuberculosis, was used as the parental strain to construct the double and triple mutants Mtb⌬mbtB⌬dyP, Mtb⌬mbtB⌬mhuD, and Mtb⌬mbtB⌬mhuD⌬dyP via specialized transduction as described previously (20). To generate the Mtb⌬mbtB⌬mhuD mutant, we constructed an allelic exchange substrate by cloning a 1.9-kb PCR product, including the entire mhuD gene and flanking regions, and then replacing 222 nucleotides of the mhuD gene (encoding amino acids 10 -85 of the 105-amino acid MhuD protein) with an apramycin resistance cassette, using essentially the same strategy described previously for construction of Mtb⌬mbtB⌬mmpL11 and Mtb⌬mbtB⌬Rv0203 (20).…”

Mycobacterium tuberculosis acquires iron by cell-surface sequestration and internalization of human holo-transferrin

“…M.tb utilizes both membrane-associated mycobactins and secreted carboxymycobactins to sequester host iron [1][2][3] . In addition, this pathogen also acquires iron from haem 4 ; intracellular M.tb are known to actively recruit host iron carrier proteins transferrin and lactoferrin to the phagosomal compartment [5][6][7][8] . It is reported that carboxymycobactins remove iron from transferrin in the phagosome, while mycobactins present in the bacterial membrane transport this iron into the bacterial cytoplasm 9,10 .…”