MmpL Genes Are Associated with Mycolic Acid Metabolism in Mycobacteria and Corynebacteria

Abstract

SummaryMycolic acids are vital components of the cell wall of the tubercle bacillus Mycobacterium tuberculosis and are required for viability and virulence. While mycolic acid biosynthesis is studied extensively, components involved in mycolate transport remain unidentified. We investigated the role of large membrane proteins encoded by mmpL genes in mycolic acid transport in mycobacteria and the related corynebacteria. MmpL3 was found to be essential in mycobacteria and conditional depletion of MmpL3 in Mycobacterium smegmatis resulted in loss of cell wall mycolylation, and of the cell wall-associated glycolipid, trehalose dimycolate. In parallel, an accumulation of trehalose monomycolate (TMM) was observed, suggesting that mycolic acids were transported as TMM. In contrast to mycobacteria, we found redundancy in the role of two mmpL genes, in Corynebacterium glutamicum; a complete loss of trehalose-associated and cell wall bound corynomycolates was observed in an NCgl0228-NCgl2769 double mutant, but not in individual single mutants. Our studies highlight the role of mmpL genes in mycolic acid metabolism and identify potential new targets for anti-TB drug development.

The Mycobacterium tuberculosis MmpL11 Cell Wall Lipid Transporter Is Important for Biofilm Formation, Intracellular Growth, and Nonreplicating Persistence

“…Both MmpL3 and MmpL11 have been implicated in heme transport (44). Although import of heme or heme complexes may be one function of these transporters, our data and those of others suggest that MmpL3 and MmpL11 are lipid exporters with a primary function in cell wall biosynthesis (10,19,45). We do not think that the mmpL11 mutant bacteria are experiencing iron starvation in our studies.…”

Mutations in mmpL and in the Cell Wall Stress Stimulon Contribute to Resistance to Oxadiazole Antibiotics in Methicillin-Resistant Staphylococcus aureus

“…The S. aureus MmpL is a putative member of the resistance, nodulation, and cell division family of proteins (11,12). This protein displays a high degree of sequence similarity to the MmpL proteins of Mycobacterium tuberculosis (25% to 30% identity, 43% to 45% similarity), which are proposed to function as scaffolds for the biosynthetic machinery of cell wall-associated lipids or to function in lipid secretion (13,22,23). The observation that MmpL was mutated in the strain COL R but not in strain COL I prompted us to examine the effect of mmpL deletion on the oxadiazole resistance of S. aureus COL. We constructed a markerless in-frame mmpL deletion mutant of strain COL and determined the MICs of a variety of antibiotics against it.…”

Crystal structure of the Mycobacterium tuberculosis transcriptional regulator Rv0302

“…3). The helices of Rv0302 are designated numerically from the N-terminus as a1 (residues [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29], a2 (residues 37-44), a3 (residues 48-55), a4 (residues 58-76), a5 (residues 88-104), ). The red circles corresponding to the Rv0302 transcription factor are placed at the putative binding sites.…”

“…9 Instead, there is strong evidence that these MmpL transporters and their MmpS accessory proteins are responsible for shuttling fatty acid and lipid components of the cell wall, such as trehalose monomycolate, sulfolipids, phthiocerol dimycocerosate, diacyltrehalose, monomeromycolyl diacylglycerol, and mycolate wax ester. 3,9,11,12,[19][20][21][22][23] The regulation of MmpL protein expression and the role of MmpLs in cell wall remodeling in different environmental conditions has not been explored. Thus we capitalized on data made available by the TB Systems Biology Consortium to begin an in-depth analysis of how mmpL and mmpS genes are regulated.…”