Abstract
One of the dominant features of the biology of
Mycobacterium tuberculosis
, and other mycobacteria, is the mycobacterial cell envelope with its exceptional complex composition. Mycolic acids are major and very specific components of the cell envelope and play a key role in its architecture and impermeability. Biosynthesis of mycolic acid (MA) precursors requires two types of fatty acid synthases, FAS I and FAS II, which should work in concert in order to keep lipid homeostasis tightly regulated. Both FAS systems are regulated at their transcriptional level by specific regulatory proteins. FasR regulates components of the FAS I system, whereas MabR and FadR regulate components of the FAS II system. In this article, by constructing a tight
mabR
conditional mutant in
Mycobacterium smegmatis
mc
2
155, we demonstrated that sub-physiological levels of MabR lead to a downregulation of the
fasII
genes, inferring that this protein is a transcriptional activator of the FAS II system.
In vivo
labelling experiments and lipidomic studies carried out in the wild-type and the
mabR
conditional mutant demonstrated that under conditions of reduced levels of MabR, there is a clear inhibition of biosynthesis of MAs, with a concomitant change in their relative composition, and of other MA-containing molecules. These studies also demonstrated a change in the phospholipid composition of the membrane of the mutant strain, with a significant increase of phosphatidylinositol. Gel shift assays carried out with MabR and P
fasII
as a probe in the presence of different chain-length acyl-CoAs strongly suggest that molecules longer than C
18
can be sensed by MabR to modulate its affinity for the operator sequences that it recognizes, and in that way switch on or off the MabR-dependent promoter. Finally, we demonstrated the direct role of MabR in the upregulation of the
fasII
operon genes after isoniazid treatment.
Funder
National Institute of Allergy and Infectious Diseases
Fondo para la Investigación Científica y Tecnológica
Subject
General Biochemistry, Genetics and Molecular Biology,Immunology,General Neuroscience
Cited by
14 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献