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Loi VV, Busche T, Schnaufer F, Kalinowski J, Antelmann H. The neutrophil oxidant hypothiocyanous acid causes a thiol-specific stress response and an oxidative shift of the bacillithiol redox potential in Staphylococcus aureus. Microbiol Spectr 2023; 11:e0325223. [PMID: 37930020 PMCID: PMC10715087 DOI: 10.1128/spectrum.03252-23] [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: 09/01/2023] [Accepted: 10/02/2023] [Indexed: 11/07/2023] Open
Abstract
IMPORTANCE Staphylococcus aureus colonizes the skin and the airways but can also lead to life-threatening systemic and chronic infections. During colonization and phagocytosis by immune cells, S. aureus encounters the thiol-reactive oxidant HOSCN. The understanding of the adaptation mechanisms of S. aureus toward HOSCN stress is important to identify novel drug targets to combat multi-resistant S. aureus isolates. As a defense mechanism, S. aureus uses the flavin disulfide reductase MerA, which functions as HOSCN reductase and protects against HOSCN stress. Moreover, MerA homologs have conserved functions in HOSCN detoxification in other bacteria, including intestinal and respiratory pathogens. In this work, we studied the comprehensive thiol-reactive mode of action of HOSCN and its effect on the reversible shift of the E BSH to discover new defense mechanisms against the neutrophil oxidant. These findings provide new leads for future drug design to fight the pathogen at the sites of colonization and infections.
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Affiliation(s)
- Vu Van Loi
- Institute of Biology-Microbiology, Freie Universität Berlin, Berlin, Germany
| | - Tobias Busche
- Microbial Genomics and Biotechnology, Center for Biotechnology, Bielefeld University, Bielefeld, Germany
| | - Franziska Schnaufer
- Institute of Biology-Microbiology, Freie Universität Berlin, Berlin, Germany
| | - Jörn Kalinowski
- Microbial Genomics and Biotechnology, Center for Biotechnology, Bielefeld University, Bielefeld, Germany
| | - Haike Antelmann
- Institute of Biology-Microbiology, Freie Universität Berlin, Berlin, Germany
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2
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Capdevila DA, Edmonds KA, Campanello GC, Wu H, Gonzalez-Gutierrez G, Giedroc DP. Functional Role of Solvent Entropy and Conformational Entropy of Metal Binding in a Dynamically Driven Allosteric System. J Am Chem Soc 2018; 140:9108-9119. [PMID: 29953213 PMCID: PMC6425489 DOI: 10.1021/jacs.8b02129] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Allostery is a regulatory phenomenon whereby ligand binding to one site influences the binding of the same or a different ligand to another site on a macromolecule. The physical origins of allosteric regulation remain under intense investigation. In general terms, ligand-induced structural changes, perturbations of residue-specific dynamics, and surrounding solvent molecules all potentially contribute to the global energetics of allostery. While the role of solvent is generally well understood in regulatory events associated with major protein structural rearrangements, the degree to which protein dynamics impact solvent degrees of freedom is unclear, particularly in cases of dynamically driven allostery. With the aid of new crystal structures, extensive calorimetric and residue-specific dynamics studies over a range of time scales and temperatures, we dissect for the first time the relative degree to which changes in solvent entropy and residue-specific dynamics impact dynamically driven, allosteric inhibition of DNA binding by Zn in the zinc efflux repressor, CzrA (chromosomal zinc-regulated repressor). We show that non-native residue-specific dynamics in allosterically impaired CzrA mutants are accompanied by significant perturbations in solvent entropy that cannot be predicted from crystal structures. We conclude that functional dynamics are not necessarily restricted to protein residues but involve surface water molecules that may be responding to ligand (Zn)-mediated perturbations in protein internal motions that define the conformational ensemble, rather than major structural rearrangements.
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Affiliation(s)
- Daiana A. Capdevila
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102 United States
| | - Katherine A. Edmonds
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102 United States
| | - Gregory C. Campanello
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102 United States
| | - Hongwei Wu
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102 United States
| | - Giovanni Gonzalez-Gutierrez
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405 United States
| | - David P. Giedroc
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102 United States
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405 United States
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3
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Chung HS, Lee S, Park SJ. Oxidation Protection in Metal-Binding Peptide Motif and Its Application to Antibody for Site-Selective Conjugation. PLoS One 2016; 11:e0159451. [PMID: 27420328 PMCID: PMC4946781 DOI: 10.1371/journal.pone.0159451] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 07/01/2016] [Indexed: 11/18/2022] Open
Abstract
Here, we demonstrate that a metal ion binding motif could serve as an efficient and robust tool for site-specific conjugation strategy. Cysteine-containing metal binding motifs were constructed as single repeat or tandem repeat peptides and their metal binding characteristics were investigated. The tandem repeats of the Cysteine-Glycine-Histidine (CGH) metal ion binding motif exhibited concerted binding to Co(II) ions, suggesting that conformational transition of peptide was triggered by the sequential metal ion binding. Evaluation of the free thiol content after reduction by reducing reagent showed that metal-ion binding elicited strong retardation of cysteine oxidation in the order of Zn(II)>Ni(II)>Co(II). The CGH metal ion binding motif was then introduced to the C-terminus of antibody heavy chain and the metal ion-dependent characteristics of oxidation kinetics were investigated. As in the case of peptides, CGH-motif-introduced antibody exhibited strong dependence on metal ion binding to protect against oxidation. Zn(II)-saturated antibody with tandem repeat of CGH motif retains the cysteine reactivity as long as 22 hour even with saturating O2 condition. Metal-ion dependent fluorophore labeling clearly indicated that metal binding motifs could be employed as an efficient tool for site-specific conjugation. Whereas Trastuzumab without a metal ion binding site exhibited site-nonspecific dye conjugation, Zn(II) ion binding to antibody with a tandem repeat of CGH motif showed that fluorophores were site-specifically conjugated to the heavy chain of antibody. We believe that this strong metal ion dependence on oxidation protection and the resulting site-selective conjugation could be exploited further to develop a highly site-specific conjugation strategy for proteins that contain multiple intrinsic cysteine residues, including monoclonal antibodies.
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Affiliation(s)
- Hye-Shin Chung
- Department of Biological Sciences and Biotechnology, College of Life Science and Nano Technology, Hannam University, 1646, Yuseong-daero, Yuseong-gu, Daejeon, Korea
- Alteogen Inc., Yuseong-daero 62, Jeon-min Dong, Yuseong-gu, Daejeon, Korea
| | - Sunbae Lee
- Alteogen Inc., Yuseong-daero 62, Jeon-min Dong, Yuseong-gu, Daejeon, Korea
| | - Soon Jae Park
- Alteogen Inc., Yuseong-daero 62, Jeon-min Dong, Yuseong-gu, Daejeon, Korea
- * E-mail:
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4
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Campanello GC, Ma Z, Grossoehme NE, Guerra AJ, Ward BP, Dimarchi RD, Ye Y, Dann CE, Giedroc DP. Allosteric inhibition of a zinc-sensing transcriptional repressor: insights into the arsenic repressor (ArsR) family. J Mol Biol 2013; 425:1143-57. [PMID: 23353829 DOI: 10.1016/j.jmb.2013.01.018] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Revised: 01/13/2013] [Accepted: 01/16/2013] [Indexed: 11/18/2022]
Abstract
The molecular basis of allosteric regulation remains a subject of intense interest. Staphylococcus aureus CzrA is a member of the ubiquitous arsenic repressor (ArsR) family of bacterial homodimeric metal-sensing proteins and has emerged as a model system for understanding allosteric regulation of operator DNA binding by transition metal ions. Using unnatural amino acid substitution and a standard linkage analysis, we show that a His97' NH(ε2)...O=C His67 quaternary structural hydrogen bond is an energetically significant contributor to the magnitude of the allosteric coupling free energy, ∆Gc. A "cavity" introduced just beneath this hydrogen bond in V66A/L68V CzrA results in a significant reduction in regulation by Zn(II) despite adopting a wild-type global structure and Zn(II) binding and DNA binding affinities only minimally affected from wild type. The energetics of Zn(II) binding and heterotropic coupling free energies (∆Hc, -T∆Sc) of the double mutant are also radically altered and suggest that increased internal dynamics leads to poorer allosteric negative regulation in V66A/L68V CzrA. A statistical coupling analysis of 3000 ArsR proteins reveals a sector that links the DNA-binding determinants and the α5 Zn(II)-sensing sites through V66/L68 in CzrA. We propose that distinct regulatory sites uniquely characteristic of individual ArsR proteins result from evolution of distinct connectivities to this sector, each capable of driving the same biological outcome, transcriptional derepression.
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5
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Liu M, Crosa JH. The regulator HlyU, the repeat-in-toxin gene rtxA1, and their roles in the pathogenesis of Vibrio vulnificus infections. Microbiologyopen 2012; 1:502-13. [PMID: 23233275 PMCID: PMC3535394 DOI: 10.1002/mbo3.48] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 07/27/2012] [Accepted: 08/06/2012] [Indexed: 12/19/2022] Open
Abstract
HlyU is a master regulator that plays an essential role in the virulence of the human pathogen Vibrio vulnificus. One of the most noteworthy characteristics of HlyU regulation in this organism is its positive control of the expression of the repeat-in-toxin (RtxA1) gene, one of the most important virulence factors accounting for the fulminating and damaging nature of V. vulnificus infections. In this work, we reviewed the latest studies of RtxA1 in this bacterium and highlight the mechanism of gene regulation of rtxA1 expression by HlyU under a broader gene regulatory network.
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Affiliation(s)
- Moqing Liu
- Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, Oregon 97239, USA.
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6
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Guerra AJ, Giedroc DP. Metal site occupancy and allosteric switching in bacterial metal sensor proteins. Arch Biochem Biophys 2012; 519:210-22. [PMID: 22178748 PMCID: PMC3312040 DOI: 10.1016/j.abb.2011.11.021] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 11/23/2011] [Accepted: 11/29/2011] [Indexed: 12/22/2022]
Abstract
All prokaryotes encode a panel of metal sensor or metalloregulatory proteins that govern the expression of genes that allows an organism to quickly adapt to toxicity or deprivation of both biologically essential transition metal ions, e.g., Zn, Cu, Fe, and heavy metal pollutants. As such, metal sensor proteins can be considered arbiters of intracellular transition metal bioavailability and thus potentially control the metallation state of the metalloproteins in the cell. Metal sensor proteins are specialized allosteric proteins that regulate transcription as a result direct binding of one or two cognate metal ions, to the exclusion of all others. In most cases, the binding of the cognate metal ion induces a structural change in a protein oligomer that either activates or inhibits operator DNA binding. A quantitative measure of the degree to which a particular metal drives metalloregulation of operator DNA-binding is the allosteric coupling free energy, ΔGc. In this review, we summarize recent work directed toward understanding metal occupancy and metal selectivity of these allosteric switches in selected families of metal sensor proteins and examine the structural origins of ΔGc in the functional context a thermodynamic "set-point" model of intracellular metal homeostasis.
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Affiliation(s)
- Alfredo J. Guerra
- Department of Chemistry, Indiana University, 212 S. Hawthorne Drive, Bloomington, IN USA 47405-7102
| | - David P. Giedroc
- Department of Chemistry, Indiana University, 212 S. Hawthorne Drive, Bloomington, IN USA 47405-7102
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7
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Chakravorty DK, Wang B, Lee CW, Giedroc DP, Merz KM. Simulations of allosteric motions in the zinc sensor CzrA. J Am Chem Soc 2012; 134:3367-76. [PMID: 22007899 PMCID: PMC3288340 DOI: 10.1021/ja208047b] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The zinc sensing transcriptional repressor Staphylococcus aureus CzrA represents an excellent model system to understand how metal sensor proteins maintain cellular metal homeostasis. Zn(II) binding induces a quaternary structural switch from a "closed" conformation to a more "open" conformation, reducing the DNA binding affinity by 4 orders of magnitude. In this study, we use classical molecular dynamics and quantum mechanical/molecular mechanical molecular dynamics simulations to investigate the molecular basis for the large conformational motions and allosteric coupling free energy (~6 kcal/mol) associated with Zn(II) binding. Our simulations successfully capture the closed to open allosteric switching in DNA bound CzrA on Zn(II) binding. They reveal that zinc binding quenches global conformational sampling by CzrA, whereas DNA binding enhances the mobility of residues in the allosteric metal binding sites. These findings are in close agreement with experiments. We also identify networks of residues involved in correlated and anticorrelated motions that connect the metal binding and DNA binding sites. Our analysis of the essential dynamics shows metal ion binding to be the primary driving force for the quaternary structural change in CzrA. We also show that Zn(II) binding limits the conformational space sampled by CzrA and causes the electrostatic surface potential at the DNA binding interface to become less favorable toward DNA binding. Finally, our simulations provide strong support for a proposed hydrogen-bonding pathway that physically connects the metal binding residue, His97, to the DNA binding interface through the αR helix that is present only in the Zn(II)-bound state. Overall, our simulations provide molecular-level insights into the mechanism of allosteric regulation by CzrA and demonstrate the importance of protein motion in its biological activity.
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Affiliation(s)
- Dhruva K. Chakravorty
- Department of Chemistry and the Quantum Theory Project, 2328 New Physics Building, P.O. Box 118435, University of Florida, Gainesville, FL 32611-8435
| | - Bing Wang
- Department of Chemistry and the Quantum Theory Project, 2328 New Physics Building, P.O. Box 118435, University of Florida, Gainesville, FL 32611-8435
| | - Chul Won Lee
- Department of Chemistry, University of Indiana, Bloomington, IN 47405-7102
| | - David P. Giedroc
- Department of Chemistry, University of Indiana, Bloomington, IN 47405-7102
| | - Kenneth M. Merz
- Department of Chemistry and the Quantum Theory Project, 2328 New Physics Building, P.O. Box 118435, University of Florida, Gainesville, FL 32611-8435
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8
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Grossoehme NE, Giedroc DP. Allosteric coupling between transition metal-binding sites in homooligomeric metal sensor proteins. Methods Mol Biol 2012; 796:31-51. [PMID: 22052484 DOI: 10.1007/978-1-61779-334-9_3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Intracellular concentrations of transition metal ions are controlled at the transcriptional level by a panel of metalloregulatory proteins that collectively allow the cell to respond to changes in bioavailable metal concentration to elicit the appropriate cellular response, e.g., upregulation of genes coding for metal export or detoxification proteins in the event of metal excess. These proteins represent a specialized class of allosteric regulators that are ideal for studying ligand-mediated allostery in a comprehensive way due to the size, stability, reactivity, and the spectroscopic properties of transition metal ions as allosteric ligands. In addition to the commonly studied heterotropic regulation of metal binding and DNA binding, many of these proteins exhibit homotropic allostery, i.e., communication between two or more identical metal (ligand) binding sites on an oligomer. This chapter aims to guide the reader through the design and execution of experiments that allow quantification of the thermodynamic driving forces (ΔG (C), ΔH (C), and ΔS (C)) that govern both homotropic and heterotropic allosteric interactions in metal sensor proteins as well as the steps required to remove the influence of complex speciation from the measured parameter values.
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9
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Abstract
The intracellular availability of all biologically required transition metal ions in bacteria, e.g., Zn, Cu, Fe, as well as the detoxification of nonbiological heavy metal pollutants, is controlled at the molecular level by a panel of metalloregulatory or "metal sensor" proteins. Metal sensor proteins are specialized allosteric proteins that regulate the transcription of genes linked to transition metal homeostasis as a result of direct binding of a single metal ion or two closely related metal ions, to the exclusion of all others. In many cases, the binding of the cognate metal ion induces a structural change in a metal sensor oligomer that either activates or inhibits operator DNA binding. A quantitative measure of the degree to which a particular metal drives metalloregulation of transcription is the allosteric coupling-free energy, ΔG(c). In this chapter, we outline detailed spectroscopically derived methods for measuring metal binding affinity, K(Me), as well as ΔG(c) independent of K(Me), presented in the context of a simple coupled equilibrium scheme. Studies carried out in this way provide quantitative insights into the degree to which a particular metal ion is capable of driving allosteric switching, and via ligand substitution, the extent to which individual coordination bonds establish structural linkage of allosteric metal and operator DNA-binding sites.
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10
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Reyes-Caballero H, Lee CW, Giedroc DP. Mycobacterium tuberculosis NmtR harbors a nickel sensing site with parallels to Escherichia coli RcnR. Biochemistry 2011; 50:7941-52. [PMID: 21819125 DOI: 10.1021/bi200737a] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Mycobacterium tuberculosis NmtR is a Ni(II)/Co(II)-sensing metalloregulatory protein from the extensively studied ArsR/SmtB family. Two Ni(II) ions bind to the NmtR dimer to form octahedral coordination complexes with the following stepwise binding affinities: K(Ni1) = (1.2 ± 0.1) × 10(10) M(-1), and K(Ni2) = (0.7 ± 0.4) × 10(10) M(-1) (pH 7.0). A glutamine scanning mutagenesis approach reveals that Asp91, His93, His104, and His107, all contained within the C-terminal α5 helix, and His3 as part of the conserved α-NH(2)-Gly2-His3-Gly4 motif at the N-terminus make significant contributions to the magnitude of K(Ni). In contrast, substitution of residues from the C-terminal region, His109, Asp114, and His116, previously implicated in Ni(II) binding and metalloregulation in cells, gives rise to wild-type K(Ni) and Ni(II)-dependent allosteric coupling free energies. Interestingly, deletion of residues 112-120 from the C-terminal region (Δ111 NmtR) reduces the Ni(II) binding stoichiometry to one per dimer and greatly reduces Ni(II) responsiveness. H3Q and Δ111 NmtRs also show clear perturbations in the rank order of metal responsiveness to Ni(II), Co(II), and Zn(II) that is distinct from that of wild-type NmtR. (15)N relaxation experiments with apo-NmtR reveal that both N-terminal (residues 2-14) and C- terminal (residues 110-120) regions are unstructured in solution, and this property likely dictates the metal specificity profile characteristic of the Ni(II) sensor NmtR relative to other ArsR family regulators.
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Reyes-Caballero H, Campanello GC, Giedroc DP. Metalloregulatory proteins: metal selectivity and allosteric switching. Biophys Chem 2011; 156:103-14. [PMID: 21511390 DOI: 10.1016/j.bpc.2011.03.010] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Revised: 03/29/2011] [Accepted: 03/29/2011] [Indexed: 01/13/2023]
Abstract
Prokaryotic organisms have evolved the capacity to quickly adapt to a changing and challenging microenvironment in which the availability of both biologically required and non-essential transition metal ions can vary dramatically. In all bacteria, a panel of metalloregulatory proteins controls the expression of genes encoding membrane transporters and metal trafficking proteins that collectively manage metal homeostasis and resistance. These "metal sensors" are specialized allosteric proteins, in which the direct binding of a specific or small number of "cognate" metal ion(s) drives a conformational change in the regulator that allosterically activates or inhibits operator DNA binding, or alternatively, distorts the promoter structure thereby converting a poor promoter to a strong one. In this review, we discuss our current understanding of the features that control metal specificity of the allosteric response in these systems, and the role that structure, thermodynamics and conformational dynamics play in mediating allosteric activation or inhibition of DNA binding.
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12
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Grossoehme NE, Giedroc DP. Energetics of allosteric negative coupling in the zinc sensor S. aureus CzrA. J Am Chem Soc 2010; 131:17860-70. [PMID: 19995076 DOI: 10.1021/ja906131b] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The linked equilibria of an allosterically regulated protein are defined by the structures, residue-specific dynamics and global energetics of interconversion among all relevant allosteric states. Here, we use isothermal titration calorimetry (ITC) to probe the global thermodynamics of allosteric negative regulation of the binding of the paradigm ArsR-family zinc sensing repressor Staphylococcus aureus CzrA to the czr DNA operator (CzrO) by Zn(2+). Zn(2+) binds to the two identical binding sites on the free CzrA homodimer in two discernible steps. A larger entropic driving force Delta(-TDeltaS) of -4.7 kcal mol(-1) and a more negative DeltaC(p) characterize the binding of the first Zn(2+) relative to the second. These features suggest a modest structural transition in forming the Zn(1) state followed by a quenching of the internal dynamics on filling the second zinc site, which collectively drive homotropic negative cooperativity of Zn(2+) binding (Delta(DeltaG) = 1.8 kcal mol(-1)). Negative homotropic cooperativity also characterizes Zn(2+) binding to the CzrA*CzrO complex (Delta(DeltaG) = 1.3 kcal mol(-1)), although the underlying energetics are vastly different, with homotropic Delta(DeltaH) and Delta(-TDeltaS) values both small and slightly positive. In short, Zn(2+) binding to the complex fails to induce a large structural or dynamical change in the CzrA bound to the operator. The strong heterotropic negative linkage in this system (DeltaG(c)(t) = 6.3 kcal mol(-1)) therefore derives from the vastly different structures of the apo-CzrA and CzrA*CzrO reference states (DeltaH(c)(t) = 9.4 kcal mol(-1)) in a way that is reinforced by a global rigidification of the allosterically inhibited Zn(2) state off the DNA (TDeltaS(c)(t) = -3.1 kcal mol(-1), i.e., DeltaS(c)(t) > 0). The implications of these findings for other metalloregulatory proteins are discussed.
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Arunkumar AI, Campanello GC, Giedroc DP. Solution structure of a paradigm ArsR family zinc sensor in the DNA-bound state. Proc Natl Acad Sci U S A 2009; 106:18177-82. [PMID: 19822742 PMCID: PMC2775347 DOI: 10.1073/pnas.0905558106] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2009] [Indexed: 11/18/2022] Open
Abstract
Staphylococcus aureus CzrA is a zinc-dependent transcriptional repressor from the ubiquitous ArsR family of metal sensor proteins. Zn(II) binds to a pair of intersubunit C-terminal alpha5-sensing sites, some 15 A distant from the DNA-binding interface, and allosterically inhibits DNA binding. This regulation is characterized by a large allosteric coupling free energy (DeltaGc) of approximately +6 kcal mol(-1), the molecular origin of which is poorly understood. Here, we report the solution quaternary structure of homodimeric CzrA bound to a palindromic 28-bp czr operator, a structure that provides an opportunity to compare the two allosteric "end" states of an ArsR family sensor. Zn(II) binding drives a quaternary structural switch from a "closed" DNA-binding state to a low affinity "open" conformation as a result of a dramatic change in the relative orientations of the winged helical DNA binding domains within the dimer. Zn(II) binding also effectively quenches both rapid and intermediate timescale internal motions of apo-CzrA while stabilizing the native state ensemble. In contrast, DNA binding significantly enhances protein motions in the allosteric sites and reduces the stability of the alpha5 helices as measured by H-D solvent exchange. This study reveals how changes in the global structure and dynamics drive a long-range allosteric response in a large subfamily of bacterial metal sensor proteins, and provides insights on how other structural classes of ArsR sensor proteins may be regulated by metal binding.
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Affiliation(s)
- Alphonse I. Arunkumar
- Department of Chemistry, Indiana University, 212 South Hawthorne Drive, Bloomington, IN 47405-7102
| | - Gregory C. Campanello
- Department of Chemistry, Indiana University, 212 South Hawthorne Drive, Bloomington, IN 47405-7102
| | - David P. Giedroc
- Department of Chemistry, Indiana University, 212 South Hawthorne Drive, Bloomington, IN 47405-7102
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Eiamphungporn W, Soonsanga S, Lee JW, Helmann JD. Oxidation of a single active site suffices for the functional inactivation of the dimeric Bacillus subtilis OhrR repressor in vitro. Nucleic Acids Res 2009; 37:1174-81. [PMID: 19129220 PMCID: PMC2651793 DOI: 10.1093/nar/gkn1052] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Bacillus subtilis OhrR is a dimeric repressor that senses organic peroxides and regulates the expression of the OhrA peroxiredoxin. Derepression results from oxidation of an active site cysteine which ultimately results in formation of a mixed disulfide with a low molecular weight thiol, a cyclic sulfenamide, or overoxidation to the sulfinic or sulfonic acids. We expressed a single-chain OhrR (scOhrR) in which the two monomers were connected by a short amino-acid linker. scOhrR variants containing only one active site cysteine were fully functional as repressors and still responded, albeit with reduced efficacy, to organic peroxides in vivo. Biochemical analyses indicate that oxidation at a single active site is sufficient for derepression regardless of the fate of the active site cysteine. scOhrR with only one active site cysteine in the amino-terminal domain is inactivated at rates comparable to wild-type whereas when the active site is in the carboxyl-terminal domain the protein is inactivated much more slowly. The incomplete derepression noted for single active site variants of scOhrR in vivo is consistent with the hypothesis that protein reduction regenerates active repressor and that, in the cell, oxidation of the second active site may also contribute to derepression.
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15
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Liu T, Chen X, Ma Z, Shokes J, Hemmingsen L, Scott RA, Giedroc DP. A Cu(I)-sensing ArsR family metal sensor protein with a relaxed metal selectivity profile. Biochemistry 2008; 47:10564-75. [PMID: 18795800 DOI: 10.1021/bi801313y] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
ArsR (or ArsR/SmtB) family metalloregulatory homodimeric repressors collectively respond to a wide range of metal ion inducers in regulating homeostasis and resistance of essential and nonessential metal ions in bacteria. BxmR from the cyanobacterium Osciliatoria brevis is the first characterized ArsR protein that senses both Cu (I)/Ag (I) and divalent metals Zn (II)/Cd (II) in cells by regulating the expression of a P-type ATPase efflux pump (Bxa1) and an intracellular metallothionein (BmtA). We show here that both pairs of predicted alpha3N and alpha5 sites bind metal ions, but with distinct physicochemical and functional metal specificities. Inactivation of the thiophilic alpha3N site via mutation (C77S) abolishes regulation by both Cd (II) and Cu (I), while Zn (II) remains a potent allosteric negative effector of operator/promoter binding (Delta G c >or= +3.2 kcal mol (-1)). In contrast, alpha5 site mutant retains regulation by all four metal ions, albeit with a smaller coupling free energy (Delta G c approximately +1.7 (+/-0.1) kcal mol (-1)). Unlike the other metals ions, the BxmR dimer binds 4 mol equiv of Cu (I) to form an alpha3N binuclear Cu (I) 2S 4 cluster by X-ray absorption spectroscopy. BxmR is thus distinguishable from other closely related ArsR family sensors, in having evolved a metalloregulatory alpha3N site that can adopt an expanded range of coordination chemistries while maintaining redundancy in the response to Zn (II). The evolutionary implications of these findings for the ArsR metal sensor family are discussed.
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Affiliation(s)
- Tong Liu
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128, USA
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Arunkumar AI, Pennella MA, Kong X, Giedroc DP. Resonance assignments of the metal sensor CzrA in the apo-, Zn2- and DNA-bound (42 kDa) states. BIOMOLECULAR NMR ASSIGNMENTS 2007; 1:99-101. [PMID: 19636838 DOI: 10.1007/s12104-007-9027-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2007] [Revised: 06/13/2007] [Accepted: 06/15/2007] [Indexed: 05/28/2023]
Abstract
Zn/Co binding to homodimeric CzrA de-represses transcription of the czr (cobalt zinc resistance) operon in Staphylococcus aureus. Essentially complete backbone and stereospecific methyl group resonance assignments for apo-, Zn2 and a 42 kDa apo-CzrA-DNA complex are presented.
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Affiliation(s)
- Alphonse I Arunkumar
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-2128, USA
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Giedroc DP, Arunkumar AI. Metal sensor proteins: nature's metalloregulated allosteric switches. Dalton Trans 2007:3107-20. [PMID: 17637984 DOI: 10.1039/b706769k] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Metalloregulatory proteins control the expression of genes that allow organisms to quickly adapt to chronic toxicity or deprivation of both biologically essential metal ions and heavy metal pollutants found in their microenvironment. Emerging evidence suggests that metal ion homeostasis and resistance defines an important tug-of-war in human host-bacterial pathogen interactions. This adaptive response originates with the formation of "metal receptor" complexes of exquisite selectivity. In this perspective, we summarize consensus structural features of metal sensing coordination complexes and the evolution of distinct metal selectivities within seven characterized metal sensor protein families. In addition, we place recent efforts to understand the structural basis of metal-induced allosteric switching of these metalloregulatory proteins in a thermodynamic framework, and review the degree to which coordination chemistry drives changes in protein structure and dynamics in selected metal sensor systems. New insights into how metal sensor proteins function in the complex intracellular milieu of the cytoplasm of cells will require a more sophisticated understanding of the "metallome" and will benefit greatly from ongoing collaborative efforts in bioinorganic, biophysical and analytical chemistry, structural biology and microbiology.
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Affiliation(s)
- David P Giedroc
- Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, TX 77843-2128, USA.
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