title: AccD6, a key carboxyltransferase essential for mycolic acid synthesis in Mycobacterium tuberculosis, is dispensable in a nonpathogenic strain.
abstract: Acetyl coenzyme A carboxylase (ACC) is a key enzyme providing a substrate for mycolic acid biosynthesis. Although in vitro studies have demonstrated that the protein encoded by accD6 (Rv2247) may be a functional carboxyltransferase subunit of ACC in Mycobacterium tuberculosis, the in vivo function and regulation of accD6 in slow- and fast-growing mycobacteria remain elusive. Here, directed mutagenesis demonstrated that although accD6 is essential for M. tuberculosis, it can be deleted in Mycobacterium smegmatis without affecting its cell envelope integrity. Moreover, we showed that although it is part of the type II fatty acid synthase operon, the accD6 gene of M. tuberculosis, but not that of M. smegmatis, possesses its own additional promoter (P(acc)). The expression level of accD6(Mtb) placed only under the control of P(acc) is 10-fold lower than that in wild-type M. tuberculosis but is sufficient to sustain cell viability. Importantly, this limited expression level affects growth, mycolic acid content, and cell morphology. These results provide the first in vivo evidence for AccD6 as a key player in the mycolate biosynthesis of M. tuberculosis, implicating AccD6 as the essential ACC subunit in pathogenic mycobacteria and an excellent target for new antitubercular compounds. Our findings also highlight important differences in the mechanism of acetyl carboxylation between pathogenic and nonpathogenic mycobacterial species.
authors: Institute for Medical Biology, Polish Academy of Sciences, Lodowa 106, 93-232 Lodz, Poland.
authors: Jakub
authors: J
authors: Pawelczyk
authors: Anna
authors: A
authors: Brzostek
authors: Laurent
authors: L
authors: Kremer
authors: Bozena
authors: B
authors: Dziadek
authors: Anna
authors: A
authors: Rumijowska-Galewicz
authors: Marta
authors: M
authors: Fiolka
authors: Jaroslaw
authors: J
authors: Dziadek
mesh_terms: D000103:Acetyl-CoA Carboxylase / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D053898:Biosynthetic Pathways; D017353:Gene Deletion; D020102:Mycobacterium smegmatis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D009171:Mycolic Acids / Q000378:metabolism*; D014376:Tuberculosis / Q000382:microbiology*
chemical_list: D001426:Bacterial Proteins; D009171:Mycolic Acids; D000103:Acetyl-CoA Carboxylase