Publications

• Flying under the radar: The non-canonical biochemistry and molecular biology of petrobactin from Bacillus anthracis.

  Hagan A.K., Carlson P.E. Jr., Hanna P.C.

  The dramatic, rapid growth of Bacillus anthracis that occurs during systemic anthrax implies a crucial requirement for the efficient acquisition of iron. While recent advances in our understanding of B. anthracis iron acquisition systems indicate the use of strategies similar to other pathogens, t ... >> More

  The dramatic, rapid growth of Bacillus anthracis that occurs during systemic anthrax implies a crucial requirement for the efficient acquisition of iron. While recent advances in our understanding of B. anthracis iron acquisition systems indicate the use of strategies similar to other pathogens, this review focuses on unique features of the major siderophore system, petrobactin. Ways that petrobactin differs from other siderophores include: A. unique ferric iron binding moieties that allow petrobactin to evade host immune proteins; B. a biosynthetic operon that encodes enzymes from both major siderophore biosynthesis classes; C. redundancy in membrane transport systems for acquisition of Fe-petrobactin holo-complexes; and, D. regulation that appears to be controlled predominately by sensing the host-like environmental signals of temperature, CO₂ levels and oxidative stress, as opposed to canonical sensing of intracellular iron levels. We argue that these differences contribute in meaningful ways to B. anthracis pathogenesis. This review will also outline current major gaps in our understanding of the petrobactin iron acquisition system, some projected means for exploiting current knowledge, and potential future research directions. << Less

  Mol. Microbiol. 102:196-206(2016) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Siderophore-mediated iron acquisition in Bacillus anthracis and related strains.

  Hotta K., Kim C.Y., Fox D.T., Koppisch A.T.

  Recent observations have shed light on some of the endogenous iron-acquisition mechanisms of members of the Bacillus cereus sensu lato group. In particular, pathogens in the B. cereus group use siderophores with both unique chemical structures and biological roles. This review will focus on recent ... >> More

  Recent observations have shed light on some of the endogenous iron-acquisition mechanisms of members of the Bacillus cereus sensu lato group. In particular, pathogens in the B. cereus group use siderophores with both unique chemical structures and biological roles. This review will focus on recent discoveries in siderophore biosynthesis and biology in this group, which contains numerous human pathogens, most notably the causative agent of anthrax, Bacillus anthracis. << Less

  Microbiology (Reading) 156:1918-1925(2010) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Functional and structural analysis of the siderophore synthetase AsbB through reconstitution of the petrobactin biosynthetic pathway from Bacillus anthracis.

  Nusca T.D., Kim Y., Maltseva N., Lee J.Y., Eschenfeldt W., Stols L., Schofield M.M., Scaglione J.B., Dixon S.D., Oves-Costales D., Challis G.L., Hanna P.C., Pfleger B.F., Joachimiak A., Sherman D.H.

  Petrobactin, a mixed catechol-carboxylate siderophore, is required for full virulence of Bacillus anthracis, the causative agent of anthrax. The asbABCDEF operon encodes the biosynthetic machinery for this secondary metabolite. Here, we show that the function of five gene products encoded by the a ... >> More

  Petrobactin, a mixed catechol-carboxylate siderophore, is required for full virulence of Bacillus anthracis, the causative agent of anthrax. The asbABCDEF operon encodes the biosynthetic machinery for this secondary metabolite. Here, we show that the function of five gene products encoded by the asb operon is necessary and sufficient for conversion of endogenous precursors to petrobactin using an in vitro system. In this pathway, the siderophore synthetase AsbB catalyzes formation of amide bonds crucial for petrobactin assembly through use of biosynthetic intermediates, as opposed to primary metabolites, as carboxylate donors. In solving the crystal structure of the B. anthracis siderophore biosynthesis protein B (AsbB), we disclose a three-dimensional model of a nonribosomal peptide synthetase-independent siderophore (NIS) synthetase. Structural characteristics provide new insight into how this bifunctional condensing enzyme can bind and adenylate multiple citrate-containing substrates followed by incorporation of both natural and unnatural polyamine nucleophiles. This activity enables formation of multiple end-stage products leading to final assembly of petrobactin. Subsequent enzymatic assays with the nonribosomal peptide synthetase-like AsbC, AsbD, and AsbE polypeptides show that the alternative products of AsbB are further converted to petrobactin, verifying previously proposed convergent routes to formation of this siderophore. These studies identify potential therapeutic targets to halt deadly infections caused by B. anthracis and other pathogenic bacteria and suggest new avenues for the chemoenzymatic synthesis of novel compounds. << Less

  J. Biol. Chem. 287:16058-16072(2012) [PubMed] [EuropePMC]

  This publication is cited by 4 other entries.

• Characterization and analysis of early enzymes for petrobactin biosynthesis in Bacillus anthracis.

  Pfleger B.F., Lee J.Y., Somu R.V., Aldrich C.C., Hanna P.C., Sherman D.H.

  Recently, iron acquisition and, more specifically, enzymes involved in siderophore biosynthesis have become attractive targets for discovery of new antibiotics. Accordingly, targeted inhibition of the biosynthesis of petrobactin, a virulence-associated siderophore encoded by the asb locus in Bacil ... >> More

  Recently, iron acquisition and, more specifically, enzymes involved in siderophore biosynthesis have become attractive targets for discovery of new antibiotics. Accordingly, targeted inhibition of the biosynthesis of petrobactin, a virulence-associated siderophore encoded by the asb locus in Bacillus anthracis, may hold promise as a potential therapy against anthrax. This study describes the biochemical characterization of AsbC, the first reported 3,4-dihydroxybenzoic acid-AMP ligase, and a key component in the biosynthesis of DHB-spermidine (DHB-SP), the first isolable intermediate in petrobactin biosynthesis. AsbC catalyzes adenylation to the corresponding AMP ester of the unusual precursor 3,4-dihydroxybenzoate, in addition to benzoate substrates bearing hydrogen bond-donating substituents at the para and meta positions on the phenyl ring. In a second reaction, AsbC catalyzes transfer of the activated starter unit to AsbD, an aryl carrier protein similar to acyl and peptidyl carrier proteins that function in fatty acid, polyketide, and nonribosomal peptide biosynthesis. A third protein, AsbE, is shown to be responsible for condensation of 3,4-dihydroxybenzoyl-AsbD with spermidine, providing the DHB-spermidine arms that are linked to citrate for assembly of petrobactin. On the basis of the selective substrate profile of AsbC, a nonhydrolyzable analogue of 3,4-DHB-AMP was synthesized and shown to effectively inhibit AsbC function in vitro. << Less

  Biochemistry 46:4147-4157(2007) [PubMed] [EuropePMC]

  This publication is cited by 6 other entries.