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González-Delgado JM, Thompson PM, Andrałojć W, Gdaniec Z, Ghiladi RA, Franzen S. Comparison of the Backbone Dynamics of Dehaloperoxidase-Hemoglobin Isoenzymes. J Phys Chem B 2024; 128:3383-3397. [PMID: 38563384 DOI: 10.1021/acs.jpcb.3c07176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Dehaloperoxidase (DHP) is a multifunctional hemeprotein with a functional switch generally regulated by the chemical class of the substrate. Its two isoforms, DHP-A and DHP-B, differ by only five amino acids and have an almost identical protein fold. However, the catalytic efficiency of DHP-B for oxidation by a peroxidase mechanism ranges from 2- to 6-fold greater than that of DHP-A depending on the conditions. X-ray crystallography has shown that many substrates and ligands have nearly identical binding in the two isoenzymes, suggesting that the difference in catalytic efficiency could be due to differences in the conformational dynamics. We compared the backbone dynamics of the DHP isoenzymes at pH 7 through heteronuclear relaxation dynamics at 11.75, 16.45, and 19.97 T in combination with four 300 ns MD simulations. While the overall dynamics of the isoenzymes are similar, there are specific local differences in functional regions of each protein. In DHP-A, Phe35 undergoes a slow chemical exchange between two conformational states likely coupled to a swinging motion of Tyr34. Moreover, Asn37 undergoes fast chemical exchange in DHP-A. Given that Phe35 and Asn37 are adjacent to Tyr34 and Tyr38, it is possible that their dynamics modulate the formation and migration of the active tyrosyl radicals in DHP-A at pH 7. Another significant difference is that both distal and proximal histidines have a 15-18% smaller S2 value in DHP-B, thus their greater flexibility could account for the higher catalytic activity. The distal histidine grants substrate access to the distal pocket. The greater flexibility of the proximal histidine could also accelerate H2O2 activation at the heme Fe by increased coupling of an amino acid charge relay to stabilize the ferryl Fe(IV) oxidation state in a Poulos-Kraut "push-pull"-type peroxidase mechanism.
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Affiliation(s)
| | - Peter M Thompson
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
- Molecular Education, Technology and Research Innovation Center (METRIC), North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Witold Andrałojć
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznań, Poland
| | - Zofia Gdaniec
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznań, Poland
| | - Reza A Ghiladi
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Stefan Franzen
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
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Malewschik T, Carey LM, de Serrano V, Ghiladi RA. Bridging the functional gap between reactivity and inhibition in dehaloperoxidase B from Amphitrite ornata: Mechanistic and structural studies with 2,4- and 2,6-dihalophenols. J Inorg Biochem 2022; 236:111944. [PMID: 35969974 DOI: 10.1016/j.jinorgbio.2022.111944] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 06/29/2022] [Accepted: 07/20/2022] [Indexed: 12/15/2022]
Abstract
The multifunctional catalytic globin dehaloperoxidase (DHP) from the marine worm Amphitrite ornata was shown to catalyze the H2O2-dependent oxidation of 2,4- and 2,6-dihalophenols (DXP; X = F, Cl, Br). Product identification by LC-MS revealed multiple monomeric products with varying degrees of oxidation and/or dehalogenation, as well as oligomers with n up to 6. Mechanistic and 18O-labeling studies demonstrated sequential dihalophenol oxidation via peroxidase and peroxygenase activities. Binding studies established that 2,4-DXP (X = Cl, Br) have the highest affinities of any known DHP substrate. X-ray crystallography identified different binding positions for 2,4- and 2,6-DXP substrates in the hydrophobic distal pocket of DHP. Correlation between the number of halogens and the substrate binding orientation revealed a halogen-dependent binding motif for mono- (4-halophenol), di- (2,4- and 2,6-dihalophenol) and trihalophenols (2,4,6-trihalopenol). Taken together, the findings here on dihalophenol reactivity with DHP advance our understanding of how these compounds bridge the inhibitory and oxidative functions of their mono- and trihalophenol counterparts, respectively, and provide further insight into the protein structure-function paradigm relevant to multifunctional catalytic globins in comparison to their monofunctional analogs.
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Affiliation(s)
- Talita Malewschik
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204, United States
| | - Leiah M Carey
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204, United States
| | - Vesna de Serrano
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204, United States
| | - Reza A Ghiladi
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204, United States.
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3
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Popescu C, Dinh T, Chen H, Miller D, Washburn A, McGuire A, Dumarieh R, D'Antonio J, Ghiladi RA. Mössbauer studies of the ferryl, ferrous and ferric states of dehaloperoxidase from A. ornata. J Inorg Biochem 2022; 234:111867. [DOI: 10.1016/j.jinorgbio.2022.111867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2022] [Revised: 04/13/2022] [Accepted: 05/17/2022] [Indexed: 10/18/2022]
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Thompson MK, Shay MR, de Serrano V, Dumarieh R, Ghiladi RA, Franzen S. A new inhibition mechanism in the multifunctional catalytic hemoglobin dehaloperoxidase as revealed by the DHP A(V59W) mutant: A spectroscopic and crystallographic study. J PORPHYR PHTHALOCYA 2021. [DOI: 10.1142/s1088424621500826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
As multifunctional catalytic hemoglobins, dehaloperoxidase isoenzymes A and B (DHP A and B) are among the most versatile hemoproteins in terms of activities displayed. The ability of DHP to bind over twenty different substrates in the distal pocket might appear to resemble the promiscuousness of monooxygenase enzymes, yet there are identifiable substrate-specific interactions that can steer the type of oxidation (O-atom vs. electron transfer) that occurs inside the DHP distal pocket. Here, we have investigated the DHP A(V59W) mutant in order to probe the limits of conformational flexibility in the distal pocket as it relates to the genesis of this substrate-dependent activity differentiation. The X-ray crystal structure of the metaquo DHP A(V59W) mutant (PDB 3K3U) and the V59W mutant in complex with fluoride [denoted as DHP A(V59W-F)] (PDB 7MNH) show significant mobility of the tryptophan in the distal pocket, with two parallel conformations having W59-N[Formula: see text] H-bonded to a heme-bound ligand (H2O or F[Formula: see text], and another conformation [observed only in DHP A(V59W-F)] that brings W59 sufficiently close to the heme as to preclude axial ligand binding. UV-vis and resonance Raman spectroscopic studies show that DHP A(V59W) is 5-coordinate high spin (5cHS) at pH 5 and 6-coordinate high spin (6cHS) at pH 7, whereas DHP A(V59W-F) is 6cHS from pH 5 to 7. Enzyme assays confirm robust peroxidase activity at pH 5, but complete loss of activity at pH 7. We find no evidence that tryptophan plays a role in the oxidation mechanism ([Formula: see text]. radical formation). Instead, the data reveal a new mechanism of DHP inhibition, namely a shift towards a non-reactive form by OH[Formula: see text] ligation to the heme-Fe that is strongly stabilized (presumably through H-bonding interactions) by the presence of W59 in the distal cavity.
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Affiliation(s)
- Matthew K. Thompson
- Department of Chemistry & Biochemistry, University of Alabama, 250 Hackberry Lane, Tuscaloosa, AL 35487, USA
| | - Madeline R. Shay
- Department of Chemistry & Biochemistry, University of Alabama, 250 Hackberry Lane, Tuscaloosa, AL 35487, USA
| | - Vesna de Serrano
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USA
| | - Rania Dumarieh
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USA
| | - Reza A. Ghiladi
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USA
| | - Stefan Franzen
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USA
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Malewschik T, de Serrano V, McGuire AH, Ghiladi RA. The multifunctional globin dehaloperoxidase strikes again: Simultaneous peroxidase and peroxygenase mechanisms in the oxidation of EPA pollutants. Arch Biochem Biophys 2019; 673:108079. [PMID: 31445024 DOI: 10.1016/j.abb.2019.108079] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 08/19/2019] [Accepted: 08/20/2019] [Indexed: 01/25/2023]
Abstract
The multifunctional catalytic hemoglobin dehaloperoxidase (DHP) from the terebellid polychaete Amphitrite ornata was found to catalyze the H2O2-dependent oxidation of EPA Priority Pollutants (4-Me-o-cresol, 4-Cl-m-cresol and pentachlorophenol) and EPA Toxic Substances Control Act compounds (o-, m-, p-cresol and 4-Cl-o-cresol). Biochemical assays (HPLC/LC-MS) indicated formation of multiple oxidation products, including the corresponding catechol, 2-methylbenzoquinone (2-MeBq), and oligomers with varying degrees of oxidation and/or dehalogenation. Using 4-Br-o-cresol as a representative substrate, labeling studies with 18O confirmed that the O-atom incorporated into the catechol was derived exclusively from H2O2, whereas the O-atom incorporated into 2-MeBq was from H2O, consistent with this single substrate being oxidized by both peroxygenase and peroxidase mechanisms, respectively. Stopped-flow UV-visible spectroscopic studies strongly implicate a role for Compound I in the peroxygenase mechanism leading to catechol formation, and for Compounds I and ES in the peroxidase mechanism that yields the 2-MeBq product. The X-ray crystal structures of DHP bound with 4-F-o-cresol (1.42 Å; PDB 6ONG), 4-Cl-o-cresol (1.50 Å; PDB 6ONK), 4-Br-o-cresol (1.70 Å; PDB 6ONX), 4-NO2-o-cresol (1.80 Å; PDB 6ONZ), o-cresol (1.60 Å; PDB 6OO1), p-cresol (2.10 Å; PDB 6OO6), 4-Me-o-cresol (1.35 Å; PDB 6ONR) and pentachlorophenol (1.80 Å; PDB 6OO8) revealed substrate binding sites in the distal pocket in close proximity to the heme cofactor, consistent with both oxidation mechanisms. The findings establish cresols as a new class of substrate for DHP, demonstrate that multiple oxidation mechanisms may exist for a given substrate, and provide further evidence that different substituents can serve as functional switches between the different activities performed by dehaloperoxidase. More broadly, the results demonstrate the complexities of marine pollution where both microbial and non-microbial systems may play significant roles in the biotransformations of EPA-classified pollutants, and further reinforces that heterocyclic compounds of anthropogenic origin should be considered as environmental stressors of infaunal organisms.
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Affiliation(s)
- Talita Malewschik
- Department of Chemistry, North Carolina State University, Raleigh, NC, 27695-8204, USA
| | - Vesna de Serrano
- Department of Chemistry, North Carolina State University, Raleigh, NC, 27695-8204, USA
| | - Ashlyn H McGuire
- Department of Chemistry, North Carolina State University, Raleigh, NC, 27695-8204, USA
| | - Reza A Ghiladi
- Department of Chemistry, North Carolina State University, Raleigh, NC, 27695-8204, USA.
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7
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Hayashi T, Hilvert D, Green AP. Engineered Metalloenzymes with Non-Canonical Coordination Environments. Chemistry 2018; 24:11821-11830. [PMID: 29786902 DOI: 10.1002/chem.201800975] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Indexed: 11/09/2022]
Abstract
Nature employs a limited number of genetically encoded, metal-coordinating residues to create metalloenzymes with diverse structures and functions. Engineered components of the cellular translation machinery can now be exploited to encode non-canonical ligands with user-defined electronic and structural properties. This ability to install "chemically programmed" ligands into proteins can provide powerful chemical probes of metalloenzyme mechanism and presents excellent opportunities to create metalloprotein catalysts with augmented properties and novel activities. In this Concept article, we provide an overview of several recent studies describing the creation of engineered metalloenzymes with interesting catalytic properties, and reveal how characterization of these systems has advanced our understanding of nature's bioinorganic mechanisms. We also highlight how powerful laboratory evolution protocols can be readily adapted to allow optimization of metalloenzymes with non-canonical ligands. This approach combines beneficial features of small molecule and protein catalysis by allowing the installation of a greater variety of local metal coordination environments into evolvable protein scaffolds, and holds great promise for the future creation of powerful metalloprotein catalysts for a host of synthetically valuable transformations.
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Affiliation(s)
- Takahiro Hayashi
- Laboratory of Organic Chemistry, ETH Zurich, 8093, Zurich, Switzerland
| | - Donald Hilvert
- Laboratory of Organic Chemistry, ETH Zurich, 8093, Zurich, Switzerland
| | - Anthony P Green
- School of Chemistry & Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
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8
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Carey LM, Gavenko R, Svistunenko DA, Ghiladi RA. How nature tunes isoenzyme activity in the multifunctional catalytic globin dehaloperoxidase from Amphitrite ornata. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2018; 1866:230-241. [DOI: 10.1016/j.bbapap.2017.11.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 11/05/2017] [Accepted: 11/07/2017] [Indexed: 01/29/2023]
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Selective tuning of activity in a multifunctional enzyme as revealed in the F21W mutant of dehaloperoxidase B from Amphitrite ornata. J Biol Inorg Chem 2017; 23:209-219. [DOI: 10.1007/s00775-017-1520-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 11/17/2017] [Indexed: 11/25/2022]
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10
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McCombs NL, Moreno-Chicano T, Carey LM, Franzen S, Hough MA, Ghiladi RA. Interaction of Azole-Based Environmental Pollutants with the Coelomic Hemoglobin from Amphitrite ornata: A Molecular Basis for Toxicity. Biochemistry 2017; 56:2294-2303. [PMID: 28387506 DOI: 10.1021/acs.biochem.7b00041] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The toxicities of azole pollutants that have widespread agricultural and industrial uses are either poorly understood or unknown, particularly with respect to how infaunal organisms are impacted by this class of persistent organic pollutant. To identify a molecular basis by which azole compounds may have unforeseen toxicity on marine annelids, we examine here their impact on the multifunctional dehaloperoxidase (DHP) hemoglobin from the terebellid polychaete Amphitrite ornata. Ultraviolet-visible and resonance Raman spectroscopic studies showed an increase in the six-coordinate low-spin heme population in DHP isoenzyme B upon binding of imidazole, benzotriazole, and benzimidazole (Kd values of 52, 82, and 110 μM, respectively), suggestive of their direct binding to the heme-Fe. Accordingly, atomic-resolution X-ray crystal structures, supported by computational studies, of the DHP B complexes of benzotriazole (1.14 Å), benzimidazole (1.08 Å), imidazole (1.08 Å), and indazole (1.12 Å) revealed two ligand binding motifs, one with direct ligand binding to the heme-Fe, and another in which the ligand binds in the hydrophobic distal pocket without coordinating the heme-Fe. Taken together, the results demonstrate a new mechanism by which azole pollutants can potentially disrupt hemoglobin function, thereby improving our understanding of their impact on infaunal organisms in marine and aquatic environments.
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Affiliation(s)
- Nikolette L McCombs
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695-8204, United States
| | - Tadeo Moreno-Chicano
- School of Biological Sciences, University of Essex , Wivenhoe Park, Colchester, Essex CO4 3SQ, U.K
| | - Leiah M Carey
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695-8204, United States
| | - Stefan Franzen
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695-8204, United States
| | - Michael A Hough
- School of Biological Sciences, University of Essex , Wivenhoe Park, Colchester, Essex CO4 3SQ, U.K
| | - Reza A Ghiladi
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695-8204, United States
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11
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McCombs NL, D’Antonio J, Barrios DA, Carey LM, Ghiladi RA. Nonmicrobial Nitrophenol Degradation via Peroxygenase Activity of Dehaloperoxidase-Hemoglobin from Amphitrite ornata. Biochemistry 2016; 55:2465-78. [DOI: 10.1021/acs.biochem.6b00143] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nikolette L. McCombs
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina, 27695-8204
| | - Jennifer D’Antonio
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina, 27695-8204
| | - David A. Barrios
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina, 27695-8204
| | - Leiah M. Carey
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina, 27695-8204
| | - Reza A. Ghiladi
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina, 27695-8204
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12
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Barrios DA, D'Antonio J, McCombs NL, Zhao J, Franzen S, Schmidt AC, Sombers LA, Ghiladi RA. Peroxygenase and oxidase activities of dehaloperoxidase-hemoglobin from Amphitrite ornata. J Am Chem Soc 2014; 136:7914-25. [PMID: 24791647 PMCID: PMC4063182 DOI: 10.1021/ja500293c] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
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The marine globin dehaloperoxidase-hemoglobin
(DHP) from Amphitrite ornata was found to catalyze
the H2O2-dependent oxidation of monohaloindoles,
a previously
unknown class of substrate for DHP. Using 5-Br-indole as a representative
substrate, the major monooxygenated products were found to be 5-Br-2-oxindole
and 5-Br-3-oxindolenine. Isotope labeling studies confirmed that the
oxygen atom incorporated was derived exclusively from H2O2, indicative of a previously unreported peroxygenase
activity for DHP. Peroxygenase activity could be initiated from either
the ferric or oxyferrous states with equivalent substrate conversion
and product distribution. It was found that 5-Br-3-oxindole, a precursor
of the product 5-Br-3-oxindolenine, readily reduced the ferric enzyme
to the oxyferrous state, demonstrating an unusual product-driven reduction
of the enzyme. As such, DHP returns to the globin-active oxyferrous
form after peroxygenase activity ceases. Reactivity with 5-Br-3-oxindole
in the absence of H2O2 also yielded 5,5′-Br2-indigo above the expected reaction stoichiometry under aerobic
conditions, and O2-concentration studies demonstrated dioxygen
consumption. Nonenzymatic and anaerobic controls both confirmed the
requirements for DHP and molecular oxygen in the catalytic generation
of 5,5′-Br2-indigo, and together suggest a newly
identified oxidase activity for DHP.
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Affiliation(s)
- David A Barrios
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695-8204, United States
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Zhao J, de Serrano V, Franzen S. A model for the flexibility of the distal histidine in dehaloperoxidase-hemoglobin A based on X-ray crystal structures of the carbon monoxide adduct. Biochemistry 2014; 53:2474-82. [PMID: 24670063 PMCID: PMC4203366 DOI: 10.1021/bi5001905] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Dehaloperoxidase
hemoglobin A (DHP A) is a multifunctional hemoglobin
that appears to have evolved oxidative pathways for the degradation
of xenobiotics as a protective function that complements the oxygen
transport function. DHP A possesses at least two internal binding
sites, one for substrates and one for inhibitors, which include various
halogenated phenols and indoles. Herein, we report the X-ray crystallographic
structure of the carbonmonoxy complex (DHPCO). Unlike other DHP structures
with 6-coordinated heme, the conformation of the distal histidine
(H55) in DHPCO is primarily external or solvent exposed, despite the
fact that the heme Fe is 6-coordinated. As observed generally in globins,
DHP exhibits two distal histidine conformations (one internal and
one external). In previous structural studies, we have shown that
the distribution of H55 conformations is weighted strongly toward
the external position when the DHP heme Fe is 5-coordinated. The large
population of the external conformation of the distal histidine observed
in DHPCO crystals at pH 6.0 indicates that some structural factor
in DHP must account for the difference from other globins, which exhibit
a significant external conformation only when pH < 4.5. While the
original hypothesis suggested that interaction with a heme-Fe-bound
ligand was the determinant of H55 conformation, the current study
forces a refinement of that hypothesis. The external or open conformation
of H55 is observed to have interactions with two propionate groups
in heme, at distances of 3.82 and 2.73 Å, respectively. A relatively
weak hydrogen bonding interaction between H55 and CO, combined with
strong interactions with heme propionate (position 6), is hypothesized
to strengthen the external conformation of H55. Density function theory
(DFT) calculations were conducted to test whether there is a weaker
hydrogen bond interaction between H55 and heme bonded CO or O2. Molecular dynamics simulations were conducted to examine
how the tautomeric forms of H55 affect the dynamic motions of the
distal histidine that govern the switching between open and closed
conformations. The calculations support the modified hypothesis suggesting
a competition between the strength of interactions with heme ligand
and the heme propionates as the factors that determine the conformation
of the distal histidine.
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Affiliation(s)
- Junjie Zhao
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States
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Sun S, Sono M, Wang C, Du J, Lebioda L, Dawson JH. Influence of heme environment structure on dioxygen affinity for the dual function Amphitrite ornata hemoglobin/dehaloperoxidase. Insights into the evolutional structure-function adaptations. Arch Biochem Biophys 2014; 545:108-15. [PMID: 24440609 DOI: 10.1016/j.abb.2014.01.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Revised: 01/08/2014] [Accepted: 01/10/2014] [Indexed: 11/28/2022]
Abstract
Sea worm, Amphitrite ornata, has evolved its globin (an O(2) carrier) also to serves as a dehaloperoxidase (DHP) to detoxify haloaromatic pollutants generated by competing species. A previous mutagenesis study by our groups on both DHP and sperm whale myoglobin (SW Mb) revealed some structural factors that influence the dehaloperoxidase activities (significantly lower for Mb) of both proteins. Using an isocyanide/O(2) partition constant measurement method in this study, we have examined the effects of these structural factors on the O(2) equilibrium constants (KO2) of DHP, SW Mb, and their mutants. A clear trend of decreasing O(2) affinity and increasing catalytic activity along with the increase in the distal His N(ε)-heme iron distance is observed. An H93K/T95H Mb double mutant mimicking the DHP proximal His positioning exhibited markedly enhanced O(2) affinity, confirming the essential effect of proximal His rotation on the globin function of DHP. For DHP, the L100F, T56G and M86E variants showed the effects of distal volume, distal His flexibility and proximal electronic push, respectively, on the O(2) affinity. This study provides insights into how DHP has evolved its heme environment to gain significantly enhanced peroxidase capability without compromising its primary function as an O(2) carrier.
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Affiliation(s)
- Shengfang Sun
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, United States
| | - Masanori Sono
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, United States.
| | - Chunxue Wang
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, United States
| | - Jing Du
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, United States
| | - Lukasz Lebioda
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, United States.
| | - John H Dawson
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, United States; School of Medicine, University of South Carolina, United States.
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Khoshtariya DE, Dolidze TD, Shushanyan M, van Eldik R. Long-range electron transfer with myoglobin immobilized at Au/mixed-SAM junctions: mechanistic impact of the strong protein confinement. J Phys Chem B 2014; 118:692-706. [PMID: 24369906 DOI: 10.1021/jp4101569] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Horse muscle myoglobin (Mb) was tightly immobilized at Au-deposited ~15-Å-thick mixed-type (1:1) alkanethiol SAMs, HS-(CH₂)₁₁-COOH/HS-(CH₂)₁₁-OH, and placed in contact with buffered H₂O or D₂O solutions. Fast-scan cyclic voltammetry (CV) and a Marcus-equation-based analysis were applied to determine unimolecular standard rate constants and reorganization free energies for electron transfer (ET), under variable-temperature (15-55 °C) and -pressure (0.01-150 MPa) conditions. The CV signal was surprisingly stable and reproducible even after multiple temperature and pressure cycles. The data analysis revealed the following values: standard rate constant, 33 s⁻¹ (25 °C, 0.01 MPa, H₂O); reorganization free energy, 0.5 ± 0.1 eV (throughout); activation enthalpy, 12 ± 3 kJ mol⁻¹; activation volume, -3.1 ± 0.2 cm³ mol⁻¹; and pH-dependent solvent kinetic isotope effect (k(H)⁰/k(D)⁰), 0.7-1.4. Furthermore, the values for the rate constant and reorganization free energy are very similar to those previously found for cytochrome c electrostatically immobilized at the monocomponent Au/HS-(CH₂)₁₁-COOH junction. In vivo, Mb apparently forms a natural electrostatic complex with cytochrome b₅ (cyt-b₅) through the "dynamic" (loose) docking pattern, allowing for a slow ET that is intrinsically coupled to the water's removal from the "defective" heme iron (altogether shaping the biological repair mechanism for Mb's "met" form). In contrary, our experiments rather mimic the case of a "simple" (tight) docking of the redesigned (mutant) Mb with cyt-b₅ (Nocek et al. J. Am. Chem. Soc. 2010, 132, 6165-6175). According to our analysis, in this configuration, Mb's distal pocket (linked to the "ligand channel") seems to be arrested within the restricted configuration, allowing the rate-determining reversible ET process to be coupled only to the inner-sphere reorganization (minimal elongation/shortening of an Fe-OH₂ bond) rather than the pronounced detachment (rebinding) of water and, hence, to be much faster.
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Affiliation(s)
- Dimitri E Khoshtariya
- Department of Chemistry and Pharmacy, University of Erlangen-Nürnberg , 91058 Erlangen, Germany
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Study of the electrostatic effects of mutations on the surface of dehaloperoxidase-hemoglobin A. Biochem Biophys Res Commun 2012; 420:733-7. [DOI: 10.1016/j.bbrc.2012.03.053] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Accepted: 03/12/2012] [Indexed: 11/17/2022]
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