The Mycobacterium tuberculosis Secreted Protein Rv0203 Transfers Heme to Membrane Proteins MmpL3 and MmpL11

• Published in: The Journal of biological chemistry 2013-07, Vol.288 (30), p.21714-21728
• Main Authors: Owens, Cedric P., Chim, Nicholas, Graves, Amanda B., Harmston, Christine A., Iniguez, Angelina, Contreras, Heidi, Liptak, Matthew D., Goulding, Celia W.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Binding Sites - genetics; Biological Transport; Carrier Proteins - genetics; Carrier Proteins - metabolism; Circular Dichroism; Electron Spin Resonance Spectroscopy; Electrophoresis, Polyacrylamide Gel; Enzymology; Heme; Heme - metabolism; Heme Uptake Pathway; Hemeproteins - metabolism; Humans; Iron; Iron Acquisition; Kinetics; Membrane Proteins - genetics; Membrane Proteins - metabolism; Membrane Transport Proteins - genetics; Membrane Transport Proteins - metabolism; Metalloporphyrins - metabolism; Models, Biological; Molecular Sequence Data; Mycobacterium tuberculosis; Mycobacterium tuberculosis - genetics; Mycobacterium tuberculosis - metabolism; Protein Binding; Protein Domains; Recombinant Proteins - metabolism; Sequence Homology, Amino Acid; Transport; Tuberculosis - microbiology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M113.453076

Mycobacterium tuberculosis is the causative agent of tuberculosis, which is becoming an increasingly global public health problem due to the rise of drug-resistant strains. While residing in the human host, M. tuberculosis needs to acquire iron for its survival. M. tuberculosis has two iron uptake mechanisms, one that utilizes non-heme iron and another that taps into the vast host heme-iron pool. To date, proteins known to be involved in mycobacterial heme uptake are Rv0203, MmpL3, and MmpL11. Whereas Rv0203 transports heme across the bacterial periplasm or scavenges heme from host heme proteins, MmpL3 and MmpL11 are thought to transport heme across the membrane. In this work, we characterize the heme-binding properties of the predicted extracellular soluble E1 domains of both MmpL3 and MmpL11 utilizing absorption, electron paramagnetic resonance, and magnetic circular dichroism spectroscopic methods. Furthermore, we demonstrate that Rv0203 transfers heme to both MmpL3-E1 and MmpL11-E1 domains at a rate faster than passive heme dissociation from Rv0203. This work elucidates a key step in the mycobacterial uptake of heme, and it may be useful in the development of anti-tuberculosis drugs targeting this pathway. Background: A novel Mycobacterium tuberculosis heme acquisition has recently been discovered. Results: The membrane protein MmpL11 is required for efficient heme uptake, and secreted Rv0203 may transfer heme to extracellular domains of both MmpL3 and MmpL11. Conclusion: MmpL3 and MmpL11 are potential heme transporters, whereby heme is transported into the cytosol. Significance: This work enhances our understanding of Mycobacterium tuberculosis heme uptake.