1
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Illava G, Gillilan R, Ando N. Development of in-line anoxic small-angle X-ray scattering and structural characterization of an oxygen-sensing transcriptional regulator. J Biol Chem 2023; 299:105039. [PMID: 37442238 PMCID: PMC10425943 DOI: 10.1016/j.jbc.2023.105039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2023] [Revised: 07/01/2023] [Accepted: 07/05/2023] [Indexed: 07/15/2023] Open
Abstract
Oxygen-sensitive metalloenzymes are responsible for many of the most fundamental biochemical processes in nature, from the reduction of dinitrogen in nitrogenase to the biosynthesis of photosynthetic pigments. However, biophysical characterization of such proteins under anoxic conditions can be challenging, especially at noncryogenic temperatures. In this study, we introduce the first in-line anoxic small-angle X-ray scattering (anSAXS) system at a major national synchrotron source, featuring both batch-mode and chromatography-mode capabilities. To demonstrate chromatography-coupled anSAXS, we investigated the oligomeric interconversions of the fumarate and nitrate reduction (FNR) transcription factor, which is responsible for the transcriptional response to changing oxygen conditions in the facultative anaerobe Escherichia coli. Previous work has shown that FNR contains a labile [4Fe-4S] cluster that is degraded when oxygen is present and that this change in cluster composition leads to the dissociation of the DNA-binding dimeric form. Using anSAXS, we provide the first direct structural evidence for the oxygen-induced dissociation of the E. coli FNR dimer and its correlation with cluster composition. We further demonstrate how complex FNR-DNA interactions can be studied by investigating the promoter region of the anaerobic ribonucleotide reductase genes, nrdDG, which contains tandem FNR-binding sites. By coupling size-exclusion chromatography-anSAXS with full-spectrum UV-Vis analysis, we show that the [4Fe-4S] cluster-containing dimeric form of FNR can bind to both sites in the nrdDG promoter region. The development of in-line anSAXS greatly expands the toolbox available for the study of complex metalloproteins and provides a foundation for future expansions.
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Affiliation(s)
- Gabrielle Illava
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, USA; Center for High Energy X-ray Sciences (CHEXS), Ithaca, New York, USA
| | - Richard Gillilan
- Center for High Energy X-ray Sciences (CHEXS), Ithaca, New York, USA.
| | - Nozomi Ando
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, USA.
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2
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Carter TD, Outten FW. Ni-NTA Affinity Chromatography to Characterize Protein-Protein Interactions During Fe-S Cluster Biogenesis. Methods Mol Biol 2021; 2353:125-136. [PMID: 34292547 PMCID: PMC8969215 DOI: 10.1007/978-1-0716-1605-5_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Affinity chromatography can be repurposed to provide useful information about the specific partner protein(s) to which a protein of interest may bind as well as the relative binding affinity of that partner protein for the protein of interest. Here, we provide a protocol for an Ni-NTA affinity chromatography assay that may be utilized to uncover insightful information about the nature of protein-protein interactions during iron-sulfur (Fe-S) cluster biogenesis reactions.
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Affiliation(s)
- Terrell D Carter
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, USA
| | - F Wayne Outten
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, USA.
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3
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Silva RMB, Grodick MA, Barton JK. UvrC Coordinates an O 2-Sensitive [4Fe4S] Cofactor. J Am Chem Soc 2020; 142:10964-10977. [PMID: 32470300 DOI: 10.1021/jacs.0c01671] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Recent advances have led to numerous landmark discoveries of [4Fe4S] clusters coordinated by essential enzymes in repair, replication, and transcription across all domains of life. The cofactor has notably been challenging to observe for many nucleic acid processing enzymes due to several factors, including a weak bioinformatic signature of the coordinating cysteines and lability of the metal cofactor. To overcome these challenges, we have used sequence alignments, an anaerobic purification method, iron quantification, and UV-visible and electron paramagnetic resonance spectroscopies to investigate UvrC, the dual-incision endonuclease in the bacterial nucleotide excision repair (NER) pathway. The characteristics of UvrC are consistent with [4Fe4S] coordination with 60-70% cofactor incorporation, and additionally, we show that, bound to UvrC, the [4Fe4S] cofactor is susceptible to oxidative degradation with aggregation of apo species. Importantly, in its holo form with the cofactor bound, UvrC forms high affinity complexes with duplexed DNA substrates; the apparent dissociation constants to well-matched and damaged duplex substrates are 100 ± 20 nM and 80 ± 30 nM, respectively. This high affinity DNA binding contrasts reports made for isolated protein lacking the cofactor. Moreover, using DNA electrochemistry, we find that the cluster coordinated by UvrC is redox-active and participates in DNA-mediated charge transport chemistry with a DNA-bound midpoint potential of 90 mV vs NHE. This work highlights that the [4Fe4S] center is critical to UvrC.
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Affiliation(s)
- Rebekah M B Silva
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Michael A Grodick
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Jacqueline K Barton
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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4
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Osorio H, Mettert E, Kiley P, Dopson M, Jedlicki E, Holmes DS. Identification and Unusual Properties of the Master Regulator FNR in the Extreme Acidophile Acidithiobacillus ferrooxidans. Front Microbiol 2019; 10:1642. [PMID: 31379789 PMCID: PMC6659574 DOI: 10.3389/fmicb.2019.01642] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 07/02/2019] [Indexed: 12/28/2022] Open
Abstract
The ability to conserve energy in the presence or absence of oxygen provides a metabolic versatility that confers an advantage in natural ecosystems. The switch between alternative electron transport systems is controlled by the fumarate nitrate reduction transcription factor (FNR) that senses oxygen via an oxygen-sensitive [4Fe-4S]2+ iron-sulfur cluster. Under O2 limiting conditions, FNR plays a key role in allowing bacteria to transition from aerobic to anaerobic lifestyles. This is thought to occur via transcriptional activation of genes involved in anaerobic respiratory pathways and by repression of genes involved in aerobic energy production. The Proteobacterium Acidithiobacillus ferrooxidans is a model species for extremely acidophilic microorganisms that are capable of aerobic and anaerobic growth on elemental sulfur coupled to oxygen and ferric iron reduction, respectively. In this study, an FNR-like protein (FNRAF) was discovered in At. ferrooxidans that exhibits a primary amino acid sequence and major motifs and domains characteristic of the FNR family of proteins, including an effector binding domain with at least three of the four cysteines known to coordinate an [4Fe-4S]2+ center, a dimerization domain, and a DNA binding domain. Western blotting with antibodies against Escherichia coli FNR (FNREC) recognized FNRAF. FNRAF was able to drive expression from the FNR-responsive E. coli promoter PnarG, suggesting that it is functionally active as an FNR-like protein. Upon air exposure, FNRAF demonstrated an unusual lack of sensitivity to oxygen compared to the archetypal FNREC. Comparison of the primary amino acid sequence of FNRAF with that of other natural and mutated FNRs, including FNREC, coupled with an analysis of the predicted tertiary structure of FNRAF using the crystal structure of the related FNR from Aliivibrio fisheri as a template revealed a number of amino acid changes that could potentially stabilize FNRAF in the presence of oxygen. These include a truncated N terminus and amino acid changes both around the putative Fe-S cluster coordinating cysteines and also in the dimer interface. Increased O2 stability could allow At. ferrooxidans to survive in environments with fluctuating O2 concentrations, providing an evolutionary advantage in natural, and engineered environments where oxygen gradients shape the bacterial community.
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Affiliation(s)
- Héctor Osorio
- Center for Bioinformatics and Genome Biology, Fundación Ciencia y Vida, Santiago, Chile
| | - Erin Mettert
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI, United States
| | - Patricia Kiley
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI, United States
| | - Mark Dopson
- Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, Kalmar, Sweden
| | - Eugenia Jedlicki
- Center for Bioinformatics and Genome Biology, Fundación Ciencia y Vida, Santiago, Chile
| | - David S Holmes
- Center for Bioinformatics and Genome Biology, Fundación Ciencia y Vida, Santiago, Chile.,Universidad San Sebastian, Santiago, Chile.,Centro de Genómica y Bioinformática, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
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5
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Grossman JD, Camire EJ, Perlstein DL. Approaches to Interrogate the Role of Nucleotide Hydrolysis by Metal Trafficking NTPases: The Nbp35-Cfd1 Iron-Sulfur Cluster Scaffold as a Case Study. Methods Enzymol 2018; 599:293-325. [PMID: 29746244 DOI: 10.1016/bs.mie.2017.11.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Nucleotide hydrolases play integral yet poorly understood roles in several metallocluster biosynthetic pathways. For example, the cytosolic iron-sulfur cluster assembly (CIA) is initiated by the CIA scaffold, an ATPase which builds new iron-sulfur clusters for proteins localized to the cytosol and the nucleus in eukaryotic organisms. While in vivo studies have demonstrated the scaffold's nucleotide hydrolase domain is vital for its function, in vitro approaches have not revealed tight allosteric coupling between the cluster scaffolding site and the ATPase site. Thus, the role of ATP hydrolysis has been hard to pinpoint. Herein, we describe methods to probe the nucleotide affinity and hydrolysis activity of the CIA scaffold from yeast, which is comprised of two homologous polypeptides called Nbp35 and Cfd1. In particular, we report two different equilibrium binding assays that make use of commercially available fluorescent nucleotide analogs. Importantly, these assays can be applied to probe nucleotide affinity of both the apo- and holo-forms of the CIA scaffold. Generally, these fluorescent nucleotide analogs have been underutilized to probe metal trafficking NTPase because one of the most commonly used probes, mantATP, which is labeled with the methylanthraniloyl probe via the 2' or 3' sugar hydroxyls, has an absorption which overlaps with the UV-Vis features of many metal-binding proteins. However, by exploiting analogs like BODIPY-FL and trinitrophenyl-labeled nucleotides which have better photophysical properties for metalloprotein applications, these approaches have the potential to reveal the mechanistic underpinnings of NTPases required for metallocluster biosynthesis.
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6
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Sun J, Deng Z, Fung DKC, Yan A. Study of the Expression of Bacterial Multidrug Efflux Pumps in Anaerobic Conditions. Methods Mol Biol 2018; 1700:253-268. [PMID: 29177835 DOI: 10.1007/978-1-4939-7454-2_14] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Bacterial multidrug efflux pumps belong to a class of membrane transporter proteins that dedicate to the extrusion of a diverse range of substances out of cells including all classes of currently available antibiotics. They constitute an important mechanism of bacterial antibiotic and multidrug resistance. Since many ecological niches of bacteria and the infection foci in animal host display low oxygen tension under which condition bacterial pathogens undergo fundamental changes on their metabolic modes, it is necessary to study the expression profiles of drug efflux pumps under these physiologically and clinically relevant conditions. In this chapter, we first introduce procedures to culture bacteria under anaerobic conditions, which is achieved using screw-capped Pyrex culture tubes without agitation. We then introduce β-galactosidase activity assay using promoter-lacZ (encoding the β-galactosidase enzyme) fusion to measure the expression of efflux pumps at transcriptional level, and Western blot using chromosomal FLAG-tagged construct to examine the expression of these proteins at translational level. Applications of these gene expression studies to reveal the regulatory mechanisms of efflux genes expression as well as their physiological functions are also discussed.
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Affiliation(s)
- Jingjing Sun
- School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong SAR
| | - Ziqing Deng
- School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong SAR
| | - Danny Ka Chun Fung
- School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong SAR
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA
| | - Aixin Yan
- School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong SAR.
- Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka, Japan.
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7
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Tsai CL, Tainer JA. Robust Production, Crystallization, Structure Determination, and Analysis of [Fe-S] Proteins: Uncovering Control of Electron Shuttling and Gating in the Respiratory Metabolism of Molybdopterin Guanine Dinucleotide Enzymes. Methods Enzymol 2017; 599:157-196. [PMID: 29746239 DOI: 10.1016/bs.mie.2017.11.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
[Fe-S] clusters are essential cofactors in all domains of life. They play many biological roles due to their unique abilities for electron transfer and conformational control. Yet, producing and analyzing Fe-S proteins can be difficult and even misleading if not done anaerobically. Due to unique redox properties of [Fe-S] clusters and their oxygen sensitivity, they pose multiple challenges and can lose enzymatic activity or cause their component proteins to be structurally disordered due to [Fe-S] cluster oxidation and loss in air. Here we highlight tested protocols and strategies enabling efficient and stable [Fe-S] protein production, purification, crystallization, X-ray diffraction data collection, and structure determination. From multiple high-resolution anaerobic crystal structures, we furthermore analyze exemplary data defining [Fe-S] clusters, substrate entry, and product exit for the functional oxidation states of type II molybdo-bis(molybdopterin guanine dinucleotide) (Mo-bisMGD) enzymes. Notably, these enzymes perform electron shuttling between quinone pools and specific substrates to catalyze respiratory metabolism. The identified structure-activity relationships for this enzyme class have broad implications germane to perchlorate environments on Earth and Mars extending to an alternative mechanism underlying metabolic origins for the evolution of the oxygen atmosphere. Integrated structural analyses of type II Mo-bisMGD enzymes unveil novel distinctive shared molecular mechanisms for dynamic control of substrate entry and product release gated by hydrophobic residues. Collective findings support a prototypic model for type II Mo-bisMGD enzymes including insights for a fundamental molecular mechanistic understanding of selectivity and regulation by a conformationally gated channel with general implications for [Fe-S] cluster respiratory enzymes.
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Affiliation(s)
- Chi-Lin Tsai
- The University of Texas M. D. Anderson Cancer Center, Houston, TX, United States
| | - John A Tainer
- The University of Texas M. D. Anderson Cancer Center, Houston, TX, United States; Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA, United States.
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8
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Tanner AW, Carabetta VJ, Martinie RJ, Mashruwala AA, Boyd JM, Krebs C, Dubnau D. The RicAFT (YmcA-YlbF-YaaT) complex carries two [4Fe-4S] 2+ clusters and may respond to redox changes. Mol Microbiol 2017; 104:837-850. [PMID: 28295778 DOI: 10.1111/mmi.13667] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/11/2017] [Indexed: 01/10/2023]
Abstract
During times of environmental insult, Bacillus subtilis undergoes developmental changes leading to biofilm formation, sporulation and competence. Each of these states is regulated in part by the phosphorylated form of the master response regulator Spo0A (Spo0A∼P). The phosphorylation state of Spo0A is controlled by a multi-component phosphorelay. RicA, RicF and RicT (previously YmcA, YlbF and YaaT) have been shown to be important regulatory proteins for multiple developmental fates. These proteins directly interact and form a stable complex, which has been proposed to accelerate the phosphorelay. Indeed, this complex is sufficient to stimulate the rate of phosphotransfer amongst the phosphorelay proteins in vitro. In this study, we demonstrate that two [4Fe-4S]2+ clusters can be assembled on the complex. As with other iron-sulfur cluster-binding proteins, the complex was also found to bind FAD, hinting that these cofactors may be involved in sensing the cellular redox state. This work provides the first comprehensive characterization of an iron-sulfur protein complex that regulates Spo0A∼P levels. Phylogenetic and genetic evidence suggests that the complex plays a broader role beyond stimulation of the phosphorelay.
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Affiliation(s)
- Andrew W Tanner
- Department of Microbiology, Biochemistry and Molecular Genetics, New Jersey Medical School, Rutgers University, Newark, NJ, 07103, USA
| | - Valerie J Carabetta
- Department of Microbiology, Biochemistry and Molecular Genetics, New Jersey Medical School, Rutgers University, Newark, NJ, 07103, USA.,Public Health Research Institute Center, New Jersey Medical School, Rutgers University, Newark, NJ, 07103, USA
| | - Ryan J Martinie
- Department of Chemistry, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Ameya A Mashruwala
- Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, NJ, 08901, USA
| | - Jeffrey M Boyd
- Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, NJ, 08901, USA
| | - Carsten Krebs
- Department of Chemistry, The Pennsylvania State University, University Park, PA, 16802, USA.,Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, 16802, USA
| | - David Dubnau
- Department of Microbiology, Biochemistry and Molecular Genetics, New Jersey Medical School, Rutgers University, Newark, NJ, 07103, USA.,Public Health Research Institute Center, New Jersey Medical School, Rutgers University, Newark, NJ, 07103, USA
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9
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Youngblut MD, Tsai CL, Clark IC, Carlson HK, Maglaqui AP, Gau-Pan PS, Redford SA, Wong A, Tainer JA, Coates JD. Perchlorate Reductase Is Distinguished by Active Site Aromatic Gate Residues. J Biol Chem 2016; 291:9190-202. [PMID: 26940877 DOI: 10.1074/jbc.m116.714618] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Indexed: 11/06/2022] Open
Abstract
Perchlorate is an important ion on both Earth and Mars. Perchlorate reductase (PcrAB), a specialized member of the dimethylsulfoxide reductase superfamily, catalyzes the first step of microbial perchlorate respiration, but little is known about the biochemistry, specificity, structure, and mechanism of PcrAB. Here we characterize the biophysics and phylogeny of this enzyme and report the 1.86-Å resolution PcrAB complex crystal structure. Biochemical analysis revealed a relatively high perchlorate affinity (Km = 6 μm) and a characteristic substrate inhibition compared with the highly similar respiratory nitrate reductase NarGHI, which has a relatively much lower affinity for perchlorate (Km = 1.1 mm) and no substrate inhibition. Structural analysis of oxidized and reduced PcrAB with and without the substrate analog SeO3 (2-) bound to the active site identified key residues in the positively charged and funnel-shaped substrate access tunnel that gated substrate entrance and product release while trapping transiently produced chlorate. The structures suggest gating was associated with shifts of a Phe residue between open and closed conformations plus an Asp residue carboxylate shift between monodentate and bidentate coordination to the active site molybdenum atom. Taken together, structural and mutational analyses of gate residues suggest key roles of these gate residues for substrate entrance and product release. Our combined results provide the first detailed structural insight into the mechanism of biological perchlorate reduction, a critical component of the chlorine redox cycle on Earth.
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Affiliation(s)
| | - Chi-Lin Tsai
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and
| | | | | | | | | | | | - Alan Wong
- From the Energy Biosciences Institute and
| | - John A Tainer
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Department of Molecular and Cellular Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - John D Coates
- From the Energy Biosciences Institute and Department of Plant and Microbial Biology, University of California, Berkeley, California 94720,
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10
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Crack JC, Hutchings MI, Thomson AJ, Le Brun NE. Biochemical properties of Paracoccus denitrificans FnrP: reactions with molecular oxygen and nitric oxide. J Biol Inorg Chem 2016; 21:71-82. [PMID: 26790880 PMCID: PMC4771820 DOI: 10.1007/s00775-015-1326-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Accepted: 12/23/2015] [Indexed: 02/04/2023]
Abstract
In Paracoccus denitrificans, three CRP/FNR family regulatory proteins, NarR, NnrR and FnrP, control the switch between aerobic and anaerobic (denitrification) respiration. FnrP is a [4Fe–4S] cluster-containing homologue of the archetypal O2 sensor FNR from E. coli and accordingly regulates genes encoding aerobic and anaerobic respiratory enzymes in response to O2, and also NO, availability. Here we show that FnrP undergoes O2-driven [4Fe–4S] to [2Fe–2S] cluster conversion that involves up to 2 O2 per cluster, with significant oxidation of released cluster sulfide to sulfane observed at higher O2 concentrations. The rate of the cluster reaction was found to be ~sixfold lower than that of E. coli FNR, suggesting that FnrP can remain transcriptionally active under microaerobic conditions. This is consistent with a role for FnrP in activating expression of the high O2 affinity cytochrome c oxidase under microaerobic conditions. Cluster conversion resulted in dissociation of the transcriptionally active FnrP dimer into monomers. Therefore, along with E. coli FNR, FnrP belongs to the subset of FNR proteins in which cluster type is correlated with association state. Interestingly, two key charged residues, Arg140 and Asp154, that have been shown to play key roles in the monomer–dimer equilibrium in E. coli FNR are not conserved in FnrP, indicating that different protomer interactions are important for this equilibrium. Finally, the FnrP [4Fe–4S] cluster is shown to undergo reaction with multiple NO molecules, resulting in iron nitrosyl species and dissociation into monomers.
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Affiliation(s)
- Jason C Crack
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK.
| | - Matthew I Hutchings
- School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
| | - Andrew J Thomson
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK
| | - Nick E Le Brun
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK.
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11
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Clark IC, Youngblut M, Jacobsen G, Wetmore KM, Deutschbauer A, Lucas L, Coates JD. Genetic dissection of chlorate respiration in Pseudomonas stutzeri PDA reveals syntrophic (per)chlorate reduction. Environ Microbiol 2015; 18:3342-3354. [PMID: 26411776 DOI: 10.1111/1462-2920.13068] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 09/02/2015] [Accepted: 09/23/2015] [Indexed: 12/22/2022]
Abstract
Genes important for growth of Pseudomonas stutzeri PDA on chlorate were identified using a randomly DNA bar-coded transposon mutant library. During chlorate reduction, mutations in genes encoding the chlorate reductase clrABC, predicted molybdopterin cofactor chaperon clrD, molybdopterin biosynthesis and two genes of unknown function (clrE, clrF) had fitness defects in pooled mutant assays (Bar-seq). Markerless in-frame deletions confirmed that clrA, clrB and clrC were essential for chlorate reduction, while clrD, clrE and clrF had less severe growth defects. Interestingly, the key detoxification gene cld was essential for chlorate reduction in isogenic pure culture experiments, but showed only minor fitness defects in Bar-seq experiments. We hypothesized this was enabled through chlorite dismutation by the community, as most strains in the Bar-seq library contained an intact cld. In support of this, Δcld grew with wild-type PDA or ΔclrA, and purified Cld also restored growth to the Δcld mutant. Expanding on this, wild-type PDA and a Δcld mutant of the perchlorate reducer Azospira suillum PS grew on perchlorate in co-culture, but not individually. These results demonstrate that co-occurrence of cld and a chloroxyanion reductase within a single organism is not necessary and raises the possibility of syntrophic (per)chlorate respiration in the environment.
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Affiliation(s)
- Iain C Clark
- Department of Civil and Environmental Engineering, University of California, Berkeley, CA, 94720, USA
| | - Matt Youngblut
- Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
| | - Gillian Jacobsen
- Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
| | - Kelly M Wetmore
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Adam Deutschbauer
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Lauren Lucas
- Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
| | - John D Coates
- Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA.
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12
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Fleischhacker AS, Stubna A, Hsueh KL, Guo Y, Teter SJ, Rose JC, Brunold TC, Markley JL, Münck E, Kiley PJ. Characterization of the [2Fe-2S] cluster of Escherichia coli transcription factor IscR. Biochemistry 2012; 51:4453-62. [PMID: 22583201 DOI: 10.1021/bi3003204] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
IscR is an Fe-S cluster-containing transcription factor involved in a homeostatic mechanism that controls Fe-S cluster biogenesis in Escherichia coli. Although IscR has been proposed to act as a sensor of the cellular demands for Fe-S cluster biogenesis, the mechanism by which IscR performs this function is not known. In this study, we investigated the biochemical properties of the Fe-S cluster of IscR to gain insight into the proposed sensing activity. Mössbauer studies revealed that IscR contains predominantly a reduced [2Fe-2S](+) cluster in vivo. However, upon anaerobic isolation of IscR, some clusters became oxidized to the [2Fe-2S](2+) form. Cluster oxidation did not, however, alter the affinity of IscR for its binding site within the iscR promoter in vitro, indicating that the cluster oxidation state is not important for regulation of DNA binding. Furthermore, characterization of anaerobically isolated IscR using resonance Raman, Mössbauer, and nuclear magnetic resonance spectroscopies leads to the proposal that the [2Fe-2S] cluster does not have full cysteinyl ligation. Mutagenesis studies indicate that, in addition to the three previously identified cysteine residues (Cys92, Cys98, and Cys104), the highly conserved His107 residue is essential for cluster ligation. Thus, these data suggest that IscR binds the cluster with an atypical ligation scheme of three cysteines and one histidine, a feature that may be relevant to the proposed function of IscR as a sensor of cellular Fe-S cluster status.
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Affiliation(s)
- Angela S Fleischhacker
- Department of Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin 53706, United States
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13
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Bueno E, Mesa S, Bedmar EJ, Richardson DJ, Delgado MJ. Bacterial adaptation of respiration from oxic to microoxic and anoxic conditions: redox control. Antioxid Redox Signal 2012; 16:819-52. [PMID: 22098259 PMCID: PMC3283443 DOI: 10.1089/ars.2011.4051] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Revised: 11/16/2011] [Accepted: 11/18/2011] [Indexed: 12/22/2022]
Abstract
Under a shortage of oxygen, bacterial growth can be faced mainly by two ATP-generating mechanisms: (i) by synthesis of specific high-affinity terminal oxidases that allow bacteria to use traces of oxygen or (ii) by utilizing other substrates as final electron acceptors such as nitrate, which can be reduced to dinitrogen gas through denitrification or to ammonium. This bacterial respiratory shift from oxic to microoxic and anoxic conditions requires a regulatory strategy which ensures that cells can sense and respond to changes in oxygen tension and to the availability of other electron acceptors. Bacteria can sense oxygen by direct interaction of this molecule with a membrane protein receptor (e.g., FixL) or by interaction with a cytoplasmic transcriptional factor (e.g., Fnr). A third type of oxygen perception is based on sensing changes in redox state of molecules within the cell. Redox-responsive regulatory systems (e.g., ArcBA, RegBA/PrrBA, RoxSR, RegSR, ActSR, ResDE, and Rex) integrate the response to multiple signals (e.g., ubiquinone, menaquinone, redox active cysteine, electron transport to terminal oxidases, and NAD/NADH) and activate or repress target genes to coordinate the adaptation of bacterial respiration from oxic to anoxic conditions. Here, we provide a compilation of the current knowledge about proteins and regulatory networks involved in the redox control of the respiratory adaptation of different bacterial species to microxic and anoxic environments.
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Affiliation(s)
- Emilio Bueno
- Estación Experimental del Zaidín, CSIC, Granada, Spain
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