Rv2477c is an antibiotic-sensitive manganese-dependent ABC-F ATPase in Mycobacterium tuberculosis

The Rv2477c protein of Mycobacterium tuberculosis (Mtb) belongs to the ATP-binding cassette (ABC) subfamily F that contains proteins with tandem nucleotide-binding domains but lacking transmembrane domains. ABC-F subfamily proteins have been implicated in diverse cellular processes such as translation, antibiotic resistance, cell growth and nutrient sensing. In order to investigate the biochemical characteristics of Rv2477c, we expressed it in Escherichia coli, purified it and characterized its enzymatic functions. We show that Rv2477c displays strong ATPase activity (V_max = 45.5 nmol/mg/min; K_m = 90.5 μM) that is sensitive to orthovanadate. The ATPase activity was maximal in the presence of Mn²⁺ at pH 5.2. The Rv2477c protein was also able to hydrolyze GTP, TTP and CTP but at lower rates. Glutamate to glutamine substitutions at amino acid residues 185 and 468 in the two Walker B motifs of Rv2477c severely inhibited its ATPase activity. The antibiotics tetracycline and erythromycin, which target protein translation, were able to inhibit the ATPase activity of Rv2477c. We postulate that Rv2477c could be involved in mycobacterial protein translation and in resistance to tetracyclines and macrolides. This is the first report of the biochemical characterization of an ABC-F subfamily protein in Mtb.