The Two-Domain LysX Protein of Mycobacterium tuberculosis Is Required for Production of Lysinylated Phosphatidylglycerol and Resistance to Cationic Antimicrobial Peptides

Department of Biochemistry, The University of Texas Health Center at Tyler, Tyler, TX, USA.
PLoS Pathogens (Impact Factor: 8.06). 08/2009; 5(7):e1000534. DOI: 10.1371/journal.ppat.1000534
Source: PubMed

ABSTRACT Author Summary
The human pathogen Mycobacterium tuberculosis (Mtb) survives in the hostile intracellular environment, in part, by withstanding the actions of host-induced cationic antimicrobial peptides (CAMPs). Membrane phospholipid composition and the resultant charge could play an important role in Mtb survival within the host. Acidic phospholipids such as cardiolipin, phosphatidylinositol and its mannoside derivatives, phosphatidylglycerol, and a single basic species, phosphatidylethanolamine, are constituents of the Mtb membrane bilayer. We demonstrate that lysinylated phosphatidylglycerol (L-PG) represents another basic phospholipid and that the lysX gene, which encodes a two-domain protein with lysyl transferase and lysyl-tRNA synthase activities, is necessary for L-PG production. We show that L-PG is required for maintenance of an optimal membrane potential and resistance towards CAMPs. Phagosomes containing the lysX mutant showed an increased association with lysosomes, and the lysX mutant showed growth defects in mouse and guinea pig lungs, indicating that LysX activity is required for full virulence. Collectively, our results suggest that LysX activity, which is responsible for the production of L-PG, is necessary for maintenance of an optimal membrane potential such that the pathogen can grow optimally upon infection, presumably by withstanding the actions of CAMPs.

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Available from: Murty V Madiraju, Aug 03, 2015
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    • "The negatively charged phospholipid, 1,2-dimyristoyl-sn-glycero-3-phospho-rac- (1-glycerol) (DMPG) was selected because the bacterial cell membranes are predominantly negatively charged, being the phosphatidylglycerols one of the main components of the prokaryotic membranes (Pinheiro et al., 2013a). In addition, a mixture of DPPE:DPPG 8:2 (molar ratio) was chosen as a more complex bacterial membrane model, being the phosphatidylethanolamines in addition to the phosphatidylglycerols one of the main constituents of the bacterial membranes (Maloney et al., 2009). Moreover, this lipid mixture permits to study if the antimycobacterial compounds induce non-lamellar phases, one of the mechanisms of action of some antibiotics (Oszlanczi et al., 2010a). "
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    • "A M. tuberculosis mutant strain with a mutation that knocks out lysX is sensitive to cationic antibiotics and CAMPs. is mutant also shows an increased association with lysosome-associated membrane protein–positive vesicles and exhibits altered membrane potential compared to the wild-type strain. e complementation of the lysX gene but not mprF restored the production of Lys-PG (Maloney et al., 2009). mprF was discovered in S. aureus by screening transposon insertion libraries in mutants sensitive to gallidermin. "
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    • "Sensitivity to positively charged antibiotics and a specific CAMP of neutrophils was increased in an Mtb lysX loss-of-function mutant. Virulence of this mutant was lowered in mice and guinea pigs demonstrating a critical role of LysX in vivo (Maloney et al., 2009). The unique impermeable cell envelope of Mtb represents a physical barrier for CAMPs. "
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