M. tuberculosis Acyl CoA Carboxylase 5 complex: attractive target for drug discovery

GAGO, G.; BAZET LYONNET, B; CABRUJA, M.; DIACOVICH, L.; GRAMAJO, H

Keystone

Congreso; Keystone Symposia: Novel Therapeutic Approaches to Tuberculosis; 2014

Acyl-CoA carboxylases (ACCases) commit acyl-CoAs to the biosynthesis of all the unique lipids present in Mycobacterium tuberculosis cell envelope. M. tuberculosis has several genes coding for ACCase subunits in its genome: three α subunits (accA1?3), six β subunits (accD1?6) and one ε subunit (accE5). However, the roles of the different complexes are still not well defined. Bioinformatic, biochemical and structural analysis of M. tuberculosis ACCase 5 complex indicated that the main catalytic activity of this enzyme corresponds to that of a propionyl-CoA/acetyl-CoA carboxylase. This complex is formed by the biotynilated α subunit AccA3, the carboxyltransferase β subunit AccD5 and the small ε subunit AccE5. Studies carried out by high-density mutagenesis in M. tuberculosis suggested that the three genes are essential for the viability of this microorganism, inferring that the ACCase 5 complex has an essential activity for this bacterium. To gain insight about the metabolic relevance of this enzyme in mycobacteria, we obtained KO mutants in the genes encoding for the two subunits specifically associated with this complex. In this work, we present the characterization of the ACCase 5 complex of mycobacteria, based on the analysis of an accD5-accE5 conditional mutant generated in M. smegmatis. Altogether, our results demonstrate that, at least in M. smegmatis, AccD5 and AccE5 are part of an essential ACCase involved in lipid biosynthesis and that none of the other ACCases present in this bacterium can compensate for the loss of this complex. The results propose that accD5 and accE5 are both essential for the viability of this bacterium, and this essentiality is directly related to fatty acid and mycolic acid biosynthesis. Our results pave the way towards understanding the biological roles of ACCases, in addition to providing a new target for structure-based development of antituberculosis therapeutics.