CONICET | Buscador de Institutos y Recursos Humanos

Background and objectives: Mycobacteria have two fatty acid synthases which work in concert to synthesize fatty acids and mycolic acids. We identified two transcriptional regulators essential for mycobacterial viability: MabR, which controls the expression of fasII operon genes, and FasR, which specifically binds to fas promoter region and controls the de novo fatty acid biosynthesis. The main purpose of our studies is to understand at the molecular level how mycobacteria exert a fine control over the biosynthesis of their membranes. Methods: The characterization of the effector molecule that modulates the affinity of FasR for its target DNA was studied using EMSA, lacZ transcriptional fusions, SPR and in vitro transcription. In order to deeply understand the molecular bases of FasR activity, we performed experiments based on sitting drop vapor diffusion, to obtain the crystal structures of FasR, FasR-DNA and FasR-effector. Results and discussion: In this work, we show that long-chain acyl-CoAs are key effector molecules that coordinate the expression of the two FAS systems by binding to FasR. Furthermore, thin needles crystals of FasR were obtained in crystallization experiments in the presence of C20-CoA. Currently, we are optimizing the crystallization conditions in order to obtain diffraction data. Conclusion: We present conclusive evidences that long-chain acyl-CoAs are key effector molecules that coordinate the expression of the two FAS systems at the transcriptional level, by directly binding to FasR. A better understanding of this complex process of regulation of lipid homeostasis in mycobacteria, together with the structural characterization of this novel transcriptional regulator will greatly contribute to the development of new strategies to control this disease.