Discovery and characterization of a unique mycobacterial heme acquisition system

Departments of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 03/2011; 108(12):5051-6. DOI: 10.1073/pnas.1009516108
Source: PubMed


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.

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    • " mycobacteria ( Warrier et al . , 2012 ) . Moreover , antigen 85A and 85B have been demonstrated as promising vaccine candidates for pathogenic M . tuberculosis and MAP ( Huygen et al . , 2010 ) . Many Mycobacterial membrane protein Large ( MmpL ) genes are also associated with the mycolic acid biosynthesis of cell wall ( Varela et al . , 2012 ) . Tullius et al . ( 2011 ) have demonstrated that MmpL3 in M . tuberculosis plays a pivotal role in pathogenesis and is involved in the essential iron transport across the cell wall and membrane . MAP3641c ( probable MmpL3 ) protein is therefore also an interesting antigen for further evaluation . In addition , selected MAP1239c , MAP1240c , MAP2239 and MAP3890"

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    • "Many Mycobacterial membrane protein Large (MmpL) genes are also associated with the mycolic acid biosynthesis of cell wall (Varela et al., 2012). Tullius et al. (2011) have demonstrated that MmpL3 in M. tuberculosis plays a pivotal role in pathogenesis and is involved in the essential iron transport across the cell wall and membrane. MAP3641c (probable MmpL3) protein is therefore also an interesting antigen for further evaluation. "
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    ABSTRACT: Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of paratuberculosis disease affecting ruminants worldwide. The aim of this study was to identify potential candidate antigens and epitopes by bio and immuno-informatic tools which could be later evaluated as vaccines and/or diagnosis. 110 protein sequences were selected from MAP K-10 genome database: 48 classified as putative enzymes involved in surface polysaccharide and lipopolysaccharide synthesis, as membrane associated and secreted proteins, 32as conserved membrane proteins, and 30as absent from other mycobacterial genomes. These 110 proteins were preliminary screened for Major Histocompatibility Complex (MHC) class II affinity and promiscuity using ProPred program. In addition, subcellular localization and host protein homology was analyzed. From these analyses, 23 MAP proteins were selected for a more accurate inmunoinformatic analysis (i.e. T cell and B cell epitopes analysis) and for homology with mycobacterial proteins. Finally, eleven MAP proteins were identified as potential candidates for further immunogenic evaluation: six proteins (MAP0228c, MAP1239c, MAP2232, MAP3080, MAP3131 and MAP3890) were identified as presenting potential T cell epitopes, while 5 selected proteins (MAP0232c, MAP1240c, MAP1738, MAP2239 and MAP3641c) harbored a large numbers of epitopes predicted to induce both cell- and antibody-mediated immune responses. Moreover, immunogenicity of selected epitopes from MAP1239c were evaluated in IFN-γ release assay. In summary, eleven M. avium subsp. paratuberculosis proteins were identified by in silico analysis and need to be further evaluated for their immunodiagnostic and vaccine potential in field and mice model. Copyright © 2015. Published by Elsevier Ltd.
    Journal of Theoretical Biology 08/2015; 384. DOI:10.1016/j.jtbi.2015.08.003
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    • "MmpL3 and MmpL11 have a variety of proposed substrates: heme (616 Da; Tullius et al., 2011), TMM ($1,500 Da; Fujita et al., 2005), and MMDAG and mycolate ester wax ($1,300 and $1,600 Da, respectively; Pacheco et al., 2013); analogous to the RND transporters , they may bind these substrates primarily via their respective D1 domains. It is of interest to note that MmpL3/11 D1 domains are able to bind heme while the D2 domains do not exhibit any heme-binding abilities (Tullius et al., 2011). In addition, it was shown that MmpL3 and MmpL11 D1 domains are able to accept heme from a proposed secreted heme transporter , Rv0203 (Owens et al., 2013b), further supporting the hypothesis that the MmpL3/11 D1 domains are mainly responsible for substrate binding. "
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    ABSTRACT: Mycobacterium tuberculosis mycobacterial membrane protein large (MmpL) proteins are important in substrate transport across the inner membrane. Here, we show that MmpL proteins are classified into two phylogenetic clusters, where MmpL cluster II contains three soluble domains (D1, D2, and D3) and has two full-length members, MmpL3 and MmpL11. Significantly, MmpL3 is currently the most druggable M. tuberculosis target. We have solved the 2.4-Å MmpL11-D2 crystal structure, revealing structural homology to periplasmic porter subdomains of RND (multidrug) transporters. The resulting predicted cluster II MmpL membrane topology has D1 and D2 residing, and possibly interacting, within the periplasm. Crosslinking and biolayer interferometry experiments confirm that cluster II D1 and D2 bind with weak affinities, and guided D1-D2 heterodimeric model assemblies. The predicted full-length MmpL3 and MmpL11 structural models reveal key substrate binding and transport residues, and may serve as templates to set the stage for in silico anti-tuberculosis drug development. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Chemistry & biology 08/2015; 22(8). DOI:10.1016/j.chembiol.2015.07.013
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