More Like this

1. An interstrand DNA crosslink glycosylase aids Acinetobacter baumannii pathogenesis

   https://doi.org/10.1073/pnas.2402422121  

   Kunkle, Dillon E; Cai, Yujuan; Eichman, Brandt F; Skaar, Eric P (July 2024, Proceedings of the National Academy of Sciences)

   Maintenance of DNA integrity is essential to all forms of life. DNA damage generated by reaction with genotoxic chemicals results in deleterious mutations, genome instability, and cell death. Pathogenic bacteria encounter several genotoxic agents during infection. In keeping with this, the loss of DNA repair networks results in virulence attenuation in several bacterial species. Interstrand DNA crosslinks (ICLs) are a type of DNA lesion formed by covalent linkage of opposing DNA strands and are particularly toxic as they interfere with replication and transcription. Bacteria have evolved specialized DNA glycosylases that unhook ICLs, thereby initiating their repair. In this study, we describe AlkX, a DNA glycosylase encoded by the multidrug resistant pathogenAcinetobacter baumannii. AlkX exhibits ICL unhooking activity similar to that of itsEscherichia colihomolog YcaQ. Interrogation of the in vivo role of AlkX revealed that its loss sensitizes cells to DNA crosslinking and impairsA. baumanniicolonization of the lungs and dissemination to distal tissues during pneumonia. These results suggest that AlkX participates inA. baumanniipathogenesis and protects the bacterium from stress conditions encountered in vivo. Consistent with this, we found that acidic pH, an environment encountered during host colonization, results inA. baumanniiDNA damage and that alkXis induced by, and contributes to, defense against acidic conditions. Collectively, these studies reveal functions for a recently described class of proteins encoded in a broad range of pathogenic bacterial species. 

   more » « less
2. In Vitro Reconstitution of Fimsbactin Biosynthesis from Acinetobacter baumannii

   https://doi.org/10.1021/acschembio.2c00573  

   Yang, Jinping; Wencewicz, Timothy A. (July 2022, ACS Chemical Biology)

   He, Chuan; Seyedsayamdost, Mohammed R. (Ed.)

   Siderophores produced via non-ribosomal peptide synthetase (NRPS) pathways serve as critical virulence factors for many pathogenic bacteria. An improved knowledge of siderophore biosynthesis guides the development of inhibitors, vaccines, and other therapeutic strategies. Fimsbactin A is a mixed ligand siderophore derived from human pathogenic Acinetobacter baumannii that contains phenolate-oxazoline, catechol, and hydroxamate metal chelating groups branching from a central L-Ser tetrahedral unit via amide and ester linkages. Fimsbactin A is derived from two molecules of L-Ser, two molecules of 2,3-dihydroxybenzoic acid (DHB), and one molecule of L-Orn and is a product of the fbs biosynthetic operon. Here, we report the complete in vitro reconstitution of fimsbactin A biosynthesis in a cell-free system using purified enzymes. We demonstrate the conversion of L-Orn to N1-acetyl-N1-hydroxy-putrescine (ahPutr) via ordered action of FbsJ (decarboxylase), FbsI (flavin N-monooxygenase), and FbsK (N-acetyltransferase). We achieve conversion of L-Ser, DHB, and L-Orn to fimsbactin A using FbsIJK in combination with the NRPS modules FbsEFGH. We also demonstrate chemoenzymatic conversion of synthetic ahPutr to fimsbactin A using FbsEFGH and establish the substrate selectivity for the NRPS adenylation domains in FbsH (DHB) and FbsF (L-Ser). We assign a role for the type II thioesterase FbsM in producing the shunt metabolite 2-(2,3-dihydroxyphenyl)-4,5-dihydrooxazole-4-carboxylic acid (DHB-oxa) via cleavage of the corresponding thioester intermediate that is tethered to NRPS peptidyl carrier domains during biosynthetic assembly. We propose a mechanism for branching NRPS-derived peptides via amide and ester linkages via the dynamic equilibration of N-DHB-Ser and O-DHB-Ser thioester intermediates via hydrolysis of DHB-oxa thioester intermediates. We also propose a genetic signature for NRPS ‘branching’ in the presence of a terminating C-T-C motif (FbsG). 

   more » « less
3. Visible light‐induced photodeoxygenation of polycyclic selenophene Se ‐oxides

   https://doi.org/10.1002/poc.4144  

   Chintala, Satyanarayana M.; Throgmorton, John C.; Maness, Peter F.; McCulla, Ryan D. (September 2020, Journal of Physical Organic Chemistry)

   Abstract Photodeoxygenation of dibenzothiopheneS‐oxide (DBTO) is believed to produce ground‐state atomic oxygen [O(³P)] in solution. Compared with other reactive oxygen species (ROS), O(³P) is a unique oxidant as it is potent and selective. Derivatives of DBTO have been used as O(³P)‐precursors to oxidize variety of molecules, including plasmid DNA, proteins, lipids, thiols, and other small organic molecules. Unfortunately, the photodeoxygenation of DBTO requires ultraviolet irradiation, which is not an ideal wavelength range for biological systems, and has a low quantum yield of approximately 0.003. In this work, benzo[b]naphtho[1,2‐d]selenopheneSe‐oxide, benzo[b]naphtho[2,1‐d]selenopheneSe‐oxide, dinaphtho[2,3‐b:2’,3’‐d]selenopheneSe‐oxide, and perylo[1,12‐b,c,d]selenopheneSe‐oxide were synthesized, and their ability to utilize visible light for generating O(³P) was interrogated. Benzo[b]naphtho[1,2‐d]selenopheneSe‐oxide produces O(³P) upon irradiation centered at 420 nm. Additionally, benzo[b]naphtho[1,2‐d]selenopheneSe‐oxide, benzo[b]naphtho[2,1‐d]selenopheneSe‐oxide, and dinaphtho[2,3‐b:2’,3’‐d]selenopheneSe‐oxide produce O(³P) when irradiated with UVA light and have quantum yields of photodeoxygenation ranging from 0.009 to 0.33. This work increases the utility of photodeoxygenation by extending the range of wavelengths that can be used to generate O(³P) in solution. 

   more » « less
4. Magnetic ordering in a vanadium-organic coordination polymer using a pyrrolo[2,3- d :5,4- d ′]bis(thiazole)-based ligand

   https://doi.org/10.1039/C8RA05697H  

   Getmanenko, Yulia A.; Mullins, Christopher S.; Nesterov, Vladimir N.; Lake, Stephanie; Risko, Chad; Johnston-Halperin, Ezekiel (October 2018, RSC Advances)

   Here we present the synthesis and characterization of a hybrid vanadium-organic coordination polymer with robust magnetic order, a Curie temperature T C of ∼110 K, a coercive field of ∼5 Oe at 5 K, and a maximum mass magnetization of about half that of the benchmark ferrimagnetic vanadium(tetracyanoethylene) ∼2 (V·(TCNE) ∼2 ). This material was prepared using a new tetracyano-substituted quinoidal organic small molecule 7 based on a tricyclic heterocycle 4-hexyl-4 H -pyrrolo[2,3- d :5,4- d ′]bis(thiazole) ( C6-PBTz ). Single crystal X-ray diffraction of the 2,6-diiodo derivative of the parent C6-PBTz , showed a disordered hexyl chain and a nearly linear arrangement of the substituents in positions 2 and 6 of the tricyclic core. Density functional theory (DFT) calculations indicate that C6-PBTz -based ligand 7 is a strong acceptor with an electron affinity larger than that of TCNE and several other ligands previously used in molecular magnets. This effect is due in part to the electron-deficient thiazole rings and extended delocalization of the frontier molecular orbitals. The ligand detailed in this study, a representative example of fused heterocycle aromatic cores with extended π conjugation, introduces new opportunities for structure–magnetic-property correlation studies where the chemistry of the tricyclic heterocycles can modulate the electronic properties and the substituent at the central N -position can vary the spatial characteristics of the magnetic polymer. 

   more » « less
5. The electron transport chain of Shewanella oneidensis MR-1 can operate bidirectionally to enable microbial electrosynthesis

   https://doi.org/10.1128/aem.01387-23  

   Ford, Kathryne C.; TerAvest, Michaela A. (January 2024, Applied and Environmental Microbiology)

   Buan, Nicole R. (Ed.)

   ABSTRACT Extracellular electron transfer is a process by which bacterial cells can exchange electrons with a redox-active material located outside of the cell. InShewanella oneidensis, this process is natively used to facilitate respiration using extracellular electron acceptors such as Fe(III) or an anode. Previously, it was demonstrated that this process can be used to drive the microbial electrosynthesis (MES) of 2,3-butanediol (2,3-BDO) inS. oneidensisexogenously expressing butanediol dehydrogenase (BDH). Electrons taken into the cell from a cathode are used to generate NADH, which in turn is used to reduce acetoin to 2,3-BDO via BDH. However, generating NADH via electron uptake from a cathode is energetically unfavorable, so NADH dehydrogenases couple the reaction to proton motive force. We therefore need to maintain the proton gradient across the membrane to sustain NADH production. This work explores accomplishing this task by bidirectional electron transfer, where electrons provided by the cathode go to both NADH formation and oxygen (O₂) reduction by oxidases. We show that oxidases use trace dissolved oxygen in a microaerobic bioelectrical chemical system (BES), and the translocation of protons across the membrane during O₂reduction supports 2,3-BDO generation. Interestingly, this process is inhibited by high levels of dissolved oxygen in this system. In an aerated BES, O₂molecules react with the strong reductant (cathode) to form reactive oxygen species, resulting in cell death. IMPORTANCEMicrobial electrosynthesis (MES) is increasingly employed for the generation of specialty chemicals, such as biofuels, bioplastics, and cancer therapeutics. For these systems to be viable for industrial scale-up, it is important to understand the energetic requirements of the bacteria to mitigate unnecessary costs. This work demonstrates sustained production of an industrially relevant chemical driven by a cathode. Additionally, it optimizes a previously published system by removing any requirement for phototrophic energy, thereby removing the additional cost of providing a light source. We also demonstrate the severe impact of oxygen intrusion into bioelectrochemical systems, offering insight to future researchers aiming to work in an anaerobic environment. These studies provide insight into both the thermodynamics of electrosynthesis and the importance of the bioelectrochemical systems’ design. 

   more » « less