Publications

• Structures of Mycobacterium tuberculosis FadD10 protein reveal a new type of adenylate-forming enzyme.

  Liu Z., Ioerger T.R., Wang F., Sacchettini J.C.

  Mycobacterium tuberculosis has a group of 34 FadD proteins that belong to the adenylate-forming superfamily. They are classified as either fatty acyl-AMP ligases (FAALs) or fatty acyl-CoA ligases based on sequence analysis. FadD10, involved in the synthesis of a virulence-related lipopeptide, was ... >> More

  Mycobacterium tuberculosis has a group of 34 FadD proteins that belong to the adenylate-forming superfamily. They are classified as either fatty acyl-AMP ligases (FAALs) or fatty acyl-CoA ligases based on sequence analysis. FadD10, involved in the synthesis of a virulence-related lipopeptide, was mis-annotated as a fatty acyl-CoA ligase; however, it is in fact a FAAL that transfers fatty acids to an acyl carrier protein (Rv0100). In this study, we have determined the structures of FadD10 in both the apo-form and the complexed form with dodecanoyl-AMP, where we see for the first time an adenylate-forming enzyme that does not adopt a closed conformation for catalysis. Indeed, this novel conformation of FadD10, facilitated by its unique inter-domain and intermolecular interactions, is critical for the enzyme to carry out the acyl transfer onto Rv0100 rather than coenzyme A. This contradicts the existing model of FAALs that rely on an insertion motif for the acyltransferase specificity and thus makes FadD10 a new type of FAAL. We have also characterized the fatty acid preference of FadD10 through biological and structural analyses, and the data indicate long chain saturated fatty acids as the biological substrates of the enzyme. << Less

  J. Biol. Chem. 288:18473-18483(2013) [PubMed] [EuropePMC]

  This publication is cited by 8 other entries.

• Mechanism and regulation of mycobactin fatty acyl-AMP ligase FadD33.

  Vergnolle O., Xu H., Blanchard J.S.

  Mycobacterial siderophores are critical components for bacterial virulence in the host. Pathogenic mycobacteria synthesize iron chelating siderophores named mycobactin and carboxymycobactin to extract intracellular macrophage iron. The two siderophores differ in structure only by a lipophilic alip ... >> More

  Mycobacterial siderophores are critical components for bacterial virulence in the host. Pathogenic mycobacteria synthesize iron chelating siderophores named mycobactin and carboxymycobactin to extract intracellular macrophage iron. The two siderophores differ in structure only by a lipophilic aliphatic chain attached on the ε-amino group of the lysine mycobactin core, which is transferred by MbtK. Prior to acyl chain transfer, the lipophilic chain requires activation by a specific fatty acyl-AMP ligase FadD33 (also known as MbtM) and is then loaded onto phosphopantetheinylated acyl carrier protein (holo-MbtL) to form covalently acylated MbtL. We demonstrate that FadD33 prefers long chain saturated lipids and initial velocity studies showed that FadD33 proceeds via a Bi Uni Uni Bi ping-pong mechanism. Inhibition experiments suggest that, during the first half-reaction (adenylation), fatty acid binds first to the free enzyme, followed by ATP and the release of pyrophosphate to form the adenylate intermediate. During the second half-reaction (ligation), holo-MbtL binds to the enzyme followed by the release of products AMP and acylated MbtL. In addition, we characterized a post-translational regulation mechanism of FadD33 by the mycobacterial protein lysine acetyltransferase in a cAMP-dependent manner. FadD33 acetylation leads to enzyme inhibition, which can be reversed by the NAD(+)-dependent deacetylase, MSMEG_5175 (DAc1). To the best of our knowledge, this is the first time that bacterial siderophore synthesis has been shown to be regulated via post-translational protein acetylation. << Less

  J. Biol. Chem. 288:28116-28125(2013) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Nonprocessive [2 + 2]e- off-loading reductase domains from mycobacterial nonribosomal peptide synthetases.

  Chhabra A., Haque A.S., Pal R.K., Goyal A., Rai R., Joshi S., Panjikar S., Pasha S., Sankaranarayanan R., Gokhale R.S.

  In mycobacteria, polyketide synthases and nonribosomal peptide synthetases (NRPSs) produce complex lipidic metabolites by using a thio-template mechanism of catalysis. In this study, we demonstrate that off-loading reductase (R) domain of mycobacterial NRPSs performs two consecutive [2 + 2]e(-) re ... >> More

  In mycobacteria, polyketide synthases and nonribosomal peptide synthetases (NRPSs) produce complex lipidic metabolites by using a thio-template mechanism of catalysis. In this study, we demonstrate that off-loading reductase (R) domain of mycobacterial NRPSs performs two consecutive [2 + 2]e(-) reductions to release thioester-bound lipopeptides as corresponding alcohols, using a nonprocessive mechanism of catalysis. The first crystal structure of an R domain from Mycobacterium tuberculosis NRPS provides strong support to this mechanistic model and suggests that the displacement of intermediate would be required for cofactor recycling. We show that 4e(-) reductases produce alcohols through a committed aldehyde intermediate, and the reduction of this intermediate is at least 10 times more efficient than the thioester-substrate. Structural and biochemical studies also provide evidence for the conformational changes associated with the reductive cycle. Further, we show that the large substrate-binding pocket with a hydrophobic platform accounts for the remarkable substrate promiscuity of these domains. Our studies present an elegant example of the recruitment of a canonical short-chain dehydrogenase/reductase family member as an off-loading domain in the context of assembly-line enzymology. << Less

  Proc. Natl. Acad. Sci. U.S.A. 109:5681-5686(2012) [PubMed] [EuropePMC]

  This publication is cited by 11 other entries.

• A genetic locus required for iron acquisition in Mycobacterium tuberculosis.

  Krithika R., Marathe U., Saxena P., Ansari M.Z., Mohanty D., Gokhale R.S.

  Mycobactins are a family of membrane-associated siderophores required for Mycobacterium tuberculosis to adapt to its intracellular habitat. These lipophilic siderophores have been recently shown to directly acquire intracellular iron through lipid trafficking. Despite tremendous progress in unders ... >> More

  Mycobactins are a family of membrane-associated siderophores required for Mycobacterium tuberculosis to adapt to its intracellular habitat. These lipophilic siderophores have been recently shown to directly acquire intracellular iron through lipid trafficking. Despite tremendous progress in understanding the assembly-line enzymology of the siderophore biosynthesis, the genes as well as the mechanistic and biochemical principles involved in producing membrane-associated siderophores have not been investigated. Here, we report a biosynthetic locus that incorporates variety of aliphatic chains on the mycobactin skeleton. Cell-free reconstitution studies demonstrate that these acyl chains are directly transferred from a carrier protein on to the epsilon-amino group of lysine residue by an unidentified Rv1347c gene product. The unsaturation in the lipidic chain is produced by a novel acyl-acyl carrier protein dehydrogenase, which, in contrast to the conventional acyl-CoA dehydrogenases, is involved in the biosynthetic pathway. MbtG protein then performs the final N6-hydroxylation step. Genome-wide analysis revealed homologues of N-acyl transferase and MbtG in other pathogenic bacteria. Because iron plays a key role in the development of infectious diseases, the biosynthetic pathway described here represents an attractive target for developing new antibacterial agents. << Less

  Proc. Natl. Acad. Sci. U.S.A. 103:2069-2074(2006) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.