ACCase 5 is an essential acyl-CoA carboxylase in mycobacteria

BAZET LYONNET, B., GAGO, G. AND GRAMAJO H

Potrero de los Funes, San Luis

Congreso; XLVII Reunion anual de la Sociedad Argenitna de insestigacion en bioquimica y biologia molecular; 2011

Sociedad Argenitna de insestigacion en bioquimica y biologia molecular

Mycolic acids are essential for the survival, virulence and antibiotic resistance of the human pathogen Mycobacterium tuberculosis. Two acyl-CoA carboxylases, ACCase 5 and ACCase 6, carboxylate both acetyl- and propionyl-CoA to produce malonyl- and methylmalonyl-CoA, the building blocks for fatty acid, mycolic and mycocerosic acid biosynthesis. ACCase 6 is a dedicated acetyl-CoA carboxylase in vivo, and in vitro experiments showed that ACCase 5 carboxylate propionyl-CoA more efficiently than acetyl-CoA. To find out the physiological role of ACCase 5, we constructed a conditional mutant in the Mycobacterium smegmatis carboxyltransferase gene accD5, in which the addition of anhydrotetracycline (ATc) to the media turns off accD5 expression. This mutant could only be obtained in the presence of wild type copies of AccD5, and stopped growing after ATc addition, showing that AccD5 is an essential carboxyltransferase component of the ACCase 5 enzyme complex. Furthermore, we observed that, in accD5 conditional mutant cell-free extracts, propionyl-CoA carboxylase activity decreases after ATc addition, suggesting that ACCase 5 is a dedicated propionyl-CoA carboxilase in vivo, and that none of the other ACCases present in this bacterium can compensate for the loss of this activity. A more exhaustive characterization of the mutant is in progress.