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Wei CC, Razzak AA, Ghasemi H, Khedri R, Fraase A. Ca 2+ binding shifts dimeric dual oxidase's truncated EF-hand domain to monomer. Biophys Chem 2024; 312:107271. [PMID: 38852484 DOI: 10.1016/j.bpc.2024.107271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 04/17/2024] [Accepted: 05/22/2024] [Indexed: 06/11/2024]
Abstract
Hydrogen peroxide, produced by Dual Oxidase (Duox), is essential for thyroid hormone synthesis. Duox activation involves Ca2+ binding to its EF-hand Domain (EFD), which contains two EF-hands (EFs). In this study, we characterized a truncated EFD using spectrometry, calorimetry, electrophoretic mobility, and gel filtration to obtain its Ca2+ binding thermodynamic and kinetics, as well as to assess the associated conformational changes. Our results revealed that its 2nd EF-hand (EF2) exhibits a strong exothermic Ca2+ binding (Ka = 107 M-1) while EF1 shows a weaker binding (Ka = 105 M-1), resulting in the burial of its negatively charged residues. The Ca2+ binding to EFD results in a stable structure with a melting temperature shifting from 67 to 99 °C and induces a structural transition from a dimeric to monomeric form. EF2 appears to play a role in dimer formation in its apo form, while the hydrophobic exposure of Ca2+-bound-EF1 is crucial for dimer formation in its holo form. The result is consistent with structures obtained from Cryo-EM, indicating that a stable structure of EFD with hydrophobic patches upon Ca2+ binding is vital for its Duox's domain-domain interaction for electron transfer.
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Affiliation(s)
- Chin-Chuan Wei
- Department of Chemistry, College of Arts and Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA; Department of Pharmaceutical Sciences, College of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA.
| | - Amena Abdul Razzak
- Department of Chemistry, College of Arts and Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA
| | - Hadis Ghasemi
- Department of Chemistry, College of Arts and Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA
| | - Rahil Khedri
- Department of Chemistry, College of Arts and Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA
| | - Alexandria Fraase
- Department of Chemistry, College of Arts and Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA
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2
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Nguyen TA, Lee C. Thr-to-Ala Mutation Leads to a Larger Aromatic Pair and Reduced Packing Density in α1,α3-Helices during Thioredoxin Cold Adaptation. ACS OMEGA 2024; 9:10812-10824. [PMID: 38463323 PMCID: PMC10918799 DOI: 10.1021/acsomega.3c09806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 01/18/2024] [Accepted: 02/08/2024] [Indexed: 03/12/2024]
Abstract
This study investigates the impact of aromatic-aromatic interactions on the cold adaptation of thioredoxin (Trx), a small redox protein with a conserved Trx-fold structure. Two Trx orthologs, one from the psychrophilic Arctic bacterium Sphingomonas sp. (SpTrx) and the other from the mesophilic Escherichia coli (EcTrx), display distinct aromatic interactions in their α1,α3-helices. SpTrx features a larger Trp11-Phe69 pair, while EcTrx employs a smaller Phe12-Tyr70 pair along with an additional Asp9-Thr66 hydrogen bond. Smaller aromatic residues in SpTrx (Phe-Phe or Phe-Tyr pair) lead to decreased thermal and thermodynamic stabilities, increased conformational flexibility, and reduced enzyme activity. In contrast, EcTrx's thermal stability is primarily influenced by the larger Trp residue, especially in the more hydrophobic Trp-Phe pair compared to the Trp-Tyr pair. Both SpTrx and EcTrx exhibit a strengthening of the Asp-Thr hydrogen bond by a Phe-Tyr pair and a weakening by a Trp-Phe pair. Additionally, the Asp8-Thr65 hydrogen bond in SpTrx contributes to the destabilization of the Phe-Phe pair. Molecular dynamics simulations of SpTrx indicate that a smaller aromatic pair or the Asp-Thr hydrogen bond in the α1,α3-helices further destabilizes the α2-helix across the central β-sheet. Our results suggest that the Thr-to-Ala mutation destabilizes the α1,α3-helices, resulting in a larger aromatic pair and reduced packing density in psychrophilic Trxs during cold adaptation. These findings enhance our understanding of Trx's adaptation to colder temperatures.
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Affiliation(s)
- Tu Anh Nguyen
- Department of Biomedical
Science and Center for Bio-Nanomaterials, Daegu University, Gyeongsan 38453, South Korea
| | - ChangWoo Lee
- Department of Biomedical
Science and Center for Bio-Nanomaterials, Daegu University, Gyeongsan 38453, South Korea
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3
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Sastre S, Manta B, Semelak JA, Estrin D, Trujillo M, Radi R, Zeida A. Catalytic Mechanism of Mycobacterium tuberculosis Methionine Sulfoxide Reductase A. Biochemistry 2024; 63:533-544. [PMID: 38286790 DOI: 10.1021/acs.biochem.3c00504] [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: 01/31/2024]
Abstract
The oxidation of Met to methionine sulfoxide (MetSO) by oxidants such as hydrogen peroxide, hypochlorite, or peroxynitrite has profound effects on protein function. This modification can be reversed by methionine sulfoxide reductases (msr). In the context of pathogen infection, the reduction of oxidized proteins gains significance due to microbial oxidative damage generated by the immune system. For example, Mycobacterium tuberculosis (Mt) utilizes msrs (MtmsrA and MtmsrB) as part of the repair response to the host-induced oxidative stress. The absence of these enzymes makes Mycobacteria prone to increased susceptibility to cell death, pointing them out as potential therapeutic targets. This study provides a detailed characterization of the catalytic mechanism of MtmsrA using a comprehensive approach, including experimental techniques and theoretical methodologies. Confirming a ping-pong type enzymatic mechanism, we elucidate the catalytic parameters for sulfoxide and thioredoxin substrates (kcat/KM = 2656 ± 525 M-1 s-1 and 1.7 ± 0.8 × 106 M-1 s-1, respectively). Notably, the entropic nature of the activation process thermodynamics, representing ∼85% of the activation free energy at room temperature, is underscored. Furthermore, the current study questions the plausibility of a sulfurane intermediate, which may be a transition-state-like structure, suggesting the involvement of a conserved histidine residue as an acid-base catalyst in the MetSO reduction mechanism. This mechanistic insight not only advances our understanding of Mt antioxidant enzymes but also holds implications for future drug discovery and biotechnological applications.
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Affiliation(s)
- Santiago Sastre
- Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Gral Flores 2125, CP 11800 Montevideo, Uruguay
- Departamento de Biofísica, Facultad de Medicina, Universidad de la República, Gral Flores 2125, CP 11800 Montevideo, Uruguay
- Centro de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Gral Flores 2125, CP 11800 Montevideo, Uruguay
- Programa de Doctorado en Química, Facultad de Química, Universidad de la República, Gral Flores 2124, CP 11800 Montevideo, Uruguay
| | - Bruno Manta
- Institut Pasteur de Montevideo, Mataojo 2020, CP 11400 Montevideo, Uruguay
- Cátedra de Fisiopatología, Facultad de Odontología, Universidad de la República, Gral Las Heras 1925, CP 11600 Montevideo, Uruguay
| | - Jonathan A Semelak
- Departamento de Química Inorgánica, Analítica y Química Física, Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET, Ciudad Universitaria, Intendente Güiraldes 2160, CP C1428EGA Buenos Aires, Argentina
| | - Dario Estrin
- Departamento de Química Inorgánica, Analítica y Química Física, Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET, Ciudad Universitaria, Intendente Güiraldes 2160, CP C1428EGA Buenos Aires, Argentina
| | - Madia Trujillo
- Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Gral Flores 2125, CP 11800 Montevideo, Uruguay
- Centro de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Gral Flores 2125, CP 11800 Montevideo, Uruguay
| | - Rafael Radi
- Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Gral Flores 2125, CP 11800 Montevideo, Uruguay
- Centro de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Gral Flores 2125, CP 11800 Montevideo, Uruguay
| | - Ari Zeida
- Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Gral Flores 2125, CP 11800 Montevideo, Uruguay
- Centro de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Gral Flores 2125, CP 11800 Montevideo, Uruguay
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4
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Villar SF, Corrales-González L, Márquez de Los Santos B, Dalla Rizza J, Zeida A, Denicola A, Ferrer-Sueta G. Kinetic and structural assessment of the reduction of human 2-Cys peroxiredoxins by thioredoxins. FEBS J 2024; 291:778-794. [PMID: 37985387 DOI: 10.1111/febs.17006] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2023] [Revised: 10/09/2023] [Accepted: 11/16/2023] [Indexed: 11/22/2023]
Abstract
We have studied the reduction reactions of two cytosolic human peroxiredoxins (Prx) in their disulfide form by three thioredoxins (Trx; two human and one bacterial), with the aim of better understanding the rate and mechanism of those reactions, and their relevance in the context of the catalytic cycle of Prx. We have developed a new methodology based on stopped-flow and intrinsic fluorescence to study the bimolecular reactions, and found rate constants in the range of 105 -106 m-1 s-1 in all cases, showing that there is no marked kinetic preference for the expected Trx partner. By combining experimental findings and molecular dynamics studies, we found that the reactivity of the nucleophilic cysteine (CN ) in the Trx is greatly affected by the formation of the Prx-Trx complex. The protein-protein interaction forces the CN thiolate into an unfavorable hydrophobic microenvironment that reduces its hydration and results in a remarkable acceleration of the thiol-disulfide exchange reactions by more than three orders of magnitude and also produces a measurable shift in the pKa of the CN . This mechanism of activation of the thiol disulfide exchange may help understand the reduction of Prx by alternative reductants involved in redox signaling.
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Affiliation(s)
- Sebastián F Villar
- Laboratorio de Fisicoquímica Biológica, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
- Centro de Investigaciones Biomédicas (CEINBIO), Universidad de la República, Montevideo, Uruguay
| | - Laura Corrales-González
- Laboratorio de Fisicoquímica Biológica, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
| | - Belén Márquez de Los Santos
- Laboratorio de Fisicoquímica Biológica, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
- Área Inmunología, Departamento de Biociencias, Facultad de Química, Universidad de la República, Montevideo, Uruguay
| | - Joaquín Dalla Rizza
- Laboratorio de Fisicoquímica Biológica, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
| | - Ari Zeida
- Centro de Investigaciones Biomédicas (CEINBIO), Universidad de la República, Montevideo, Uruguay
- Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Ana Denicola
- Laboratorio de Fisicoquímica Biológica, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
- Centro de Investigaciones Biomédicas (CEINBIO), Universidad de la República, Montevideo, Uruguay
| | - Gerardo Ferrer-Sueta
- Laboratorio de Fisicoquímica Biológica, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
- Centro de Investigaciones Biomédicas (CEINBIO), Universidad de la República, Montevideo, Uruguay
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5
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Randall LM, Dalla Rizza J, Parsonage D, Santos J, Mehl RA, Lowther WT, Poole LB, Denicola A. Unraveling the effects of peroxiredoxin 2 nitration; role of C-terminal tyrosine 193. Free Radic Biol Med 2019; 141:492-501. [PMID: 31323313 PMCID: PMC6749834 DOI: 10.1016/j.freeradbiomed.2019.07.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 07/12/2019] [Accepted: 07/15/2019] [Indexed: 12/19/2022]
Abstract
Peroxiredoxins (Prx) are enzymes that efficiently reduce hydroperoxides through active participation of cysteine residues (CP, CR). The first step in catalysis, the reduction of peroxide substrate, is fast, 107 - 108 M-1s-1 for human Prx2. In addition, the high intracellular concentration of Prx positions them not only as good antioxidants but also as central players in redox signaling pathways. These biological functions can be affected by post-translational modifications that could alter the peroxidase activity and/or interaction with other proteins. In particular, inactivation by hyperoxidation of CP, which occurs when a second molecule of peroxide reacts with the CP in the sulfenic acid form, modulates their participation in redox signaling pathways. The higher sensitivity to hyperoxidation of some Prx has been related to the presence of structural motifs that disfavor disulfide formation at the active site, making the CP sulfenic acid more available for hyperoxidation or interaction with a redox protein target. We previously reported that treatment of human Prx2 with peroxynitrite results in tyrosine nitration, a post-translational modification on non-catalytic residues, yielding a more active peroxidase with higher resistance to hyperoxidation. In this work, studies on various mutants of hPrx2 confirm that the presence of the tyrosyl side-chain of Y193, belonging to the C-terminal YF motif of eukaryotic Prx, is necessary to observe the increase in Prx2 resistance to hyperoxidation. Moreover, our results underline the critical role of this structural motif on the rate of disulfide formation that determines the differential participation of Prx in redox signaling pathways.
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Affiliation(s)
- Lía M Randall
- Laboratorio I+D de Moléculas Bioactivas, CENUR Litoral Norte, Universidad de la República, Paysandú, Uruguay; Laboratorio de Fisicoquímica Biológica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay; Centro de Investigaciones Biomédicas, Universidad de la República, Uruguay
| | - Joaquín Dalla Rizza
- Laboratorio de Fisicoquímica Biológica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay; Centro de Investigaciones Biomédicas, Universidad de la República, Uruguay
| | - Derek Parsonage
- Department of Biochemistry and Center for Redox Biology and Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Javier Santos
- Departamento de Fisiología y Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina; Instituto de Química y Fisicoquímica Biológicas (UBA-CONICET), Buenos Aires, Argentina
| | - Ryan A Mehl
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR, USA
| | - W Todd Lowther
- Department of Biochemistry and Center for Redox Biology and Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Leslie B Poole
- Department of Biochemistry and Center for Redox Biology and Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA.
| | - Ana Denicola
- Laboratorio de Fisicoquímica Biológica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay; Centro de Investigaciones Biomédicas, Universidad de la República, Uruguay.
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6
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Dalla Rizza J, Randall LM, Santos J, Ferrer-Sueta G, Denicola A. Differential parameters between cytosolic 2-Cys peroxiredoxins, PRDX1 and PRDX2. Protein Sci 2018; 28:191-201. [PMID: 30284335 DOI: 10.1002/pro.3520] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 09/21/2018] [Accepted: 09/24/2018] [Indexed: 01/06/2023]
Abstract
Peroxiredoxins are thiol-dependent peroxidases that function in peroxide detoxification and H2 O2 induced signaling. Among the six isoforms expressed in humans, PRDX1 and PRDX2 share 97% sequence similarity, 77% sequence identity including the active site, subcellular localization (cytosolic) but they hold different biological functions albeit associated with their peroxidase activity. Using recombinant human PRDX1 and PRDX2, the kinetics of oxidation and hyperoxidation with H2 O2 and peroxynitrite were followed by intrinsic fluorescence. At pH 7.4, the peroxidatic cysteine of both isoforms reacts nearly tenfold faster with H2 O2 than with peroxynitrite, and both reactions are orders of magnitude faster than with most protein thiols. For both isoforms, the sulfenic acids formed are in turn oxidized by H2 O2 with rate constants of ca 2 × 103 M-1 s-1 and by peroxynitrous acid significantly faster. As previously observed, a crucial difference between PRDX1 and PRDX2 is on the resolution step of the catalytic cycle, the rate of disulfide formation (11 s-1 for PRDX1, 0.2 s-1 for PRDX2, independent of the oxidant) which correlates with their different sensitivity to hyperoxidation. This kinetic pause opens different pathways on redox signaling for these isoforms. The longer lifetime of PRDX2 sulfenic acid allows it to react with other protein thiols to translate the signal via an intermediate mixed disulfide (involving its peroxidatic cysteine), whereas PRDX1 continues the cycle forming disulfide involving its resolving cysteine to function as a redox relay. In addition, the presence of C83 on PRDX1 imparts a difference on peroxidase activity upon peroxynitrite exposure that needs further study.
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Affiliation(s)
- Joaquín Dalla Rizza
- Laboratorio de Fisicoquímica Biológica, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay.,Center for Free Radical and Biomedical Research, Universidad de la República, Montevideo, Uruguay
| | - Lía M Randall
- Laboratorio de Fisicoquímica Biológica, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay.,Center for Free Radical and Biomedical Research, Universidad de la República, Montevideo, Uruguay.,Laboratorio de I+D de Moléculas Bioactivas, CENUR Litoral Norte, Universidad de la República, Paysandú, Uruguay
| | - Javier Santos
- IQUIFIB (UBA-CONICET) and Departamento de Química Biológica, Facultad de Farmacia y Bioquímica, and Department of Physiology, Molecular and Cellular Biology, Universidad de Buenos Aires, Ciudad Autónoma de Buenos Aires, Argentina
| | - Gerardo Ferrer-Sueta
- Laboratorio de Fisicoquímica Biológica, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay.,Center for Free Radical and Biomedical Research, Universidad de la República, Montevideo, Uruguay
| | - Ana Denicola
- Laboratorio de Fisicoquímica Biológica, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay.,Center for Free Radical and Biomedical Research, Universidad de la República, Montevideo, Uruguay
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7
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Vazquez DS, Sánchez IE, Garrote A, Sica MP, Santos J. The E. coli thioredoxin folding mechanism: The key role of the C-terminal helix. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:127-37. [DOI: 10.1016/j.bbapap.2014.11.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2014] [Revised: 10/23/2014] [Accepted: 11/10/2014] [Indexed: 10/24/2022]
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9
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Binolfi A, Fernández CO, Sica MP, Delfino JM, Santos J. Recognition between a short unstructured peptide and a partially folded fragment leads to the thioredoxin fold sharing native-like dynamics. Proteins 2012; 80:1448-64. [DOI: 10.1002/prot.24043] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 12/27/2011] [Accepted: 01/11/2012] [Indexed: 11/09/2022]
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10
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Manta B, Obal G, Ricciardi A, Pritsch O, Denicola A. Tools to evaluate the conformation of protein products. Biotechnol J 2011; 6:731-41. [DOI: 10.1002/biot.201100107] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Revised: 03/31/2011] [Accepted: 04/04/2011] [Indexed: 11/10/2022]
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11
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Roman EA, Rosi P, González Lebrero MC, Wuilloud R, González Flecha FL, Delfino JM, Santos J. Gain of local structure in an amphipathic peptide does not require a specific tertiary framework. Proteins 2011; 78:2757-68. [PMID: 20607854 DOI: 10.1002/prot.22789] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
In this work, we studied how an amphipathic peptide of the surface of the globular protein thioredoxin, TRX94-108, acquires a native-like structure when it becomes involved in an apolar interaction network. We designed peptide variants where the tendency to form alpha-helical conformation is modulated by replacing each of the leucine amino acid residues by an alanine. The induction of structure caused by sodium dodecyl sulfate (SDS) binding was studied by capillary zone electrophoresis, circular dichroism, DOSY-NMR, and molecular dynamics simulations (MDS). In addition, we analyzed the strength of the interaction between a C18 RP-HPLC matrix and the peptides. The results presented here reveal that (a) critical elements in the sequence of the wild-type peptide stabilize a SDS/peptide supramolecular cluster; (b) the hydrophobic nature of the interaction between SDS molecules and the peptide constrains the ensemble of conformations; (c) nonspecific apolar surfaces are sufficient to stabilize peptide secondary structure. Remarkably, MDS shed light on a contact network formed by a limited number of SDS molecules that serves as a structural scaffold preserving the helical conformation of this module. This mechanism might prevail when a peptide with low helical propensity is involved in structure consolidation. We suggest that folding of peptides sharing this feature does not require a preformed tightly-packed protein core. Thus, the formation of specific tertiary interactions would be the consequence of peptide folding and not its cause. In this scenario, folding might be thought of as a process that includes unspecific rounds of structure stabilization guiding the protein to the native state.
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Affiliation(s)
- Ernesto A Roman
- Department of Biological Chemistry and Institute of Biochemistry and Biophysics (IQUIFIB), School of Pharmacy and Biochemistry, University of Buenos Aires, Junín 956, C1113AAD, Buenos Aires, Argentina
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12
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Santos J, Sica MP, Buslje CM, Garrote AM, Ermácora MR, Delfino JM. Structural selection of a native fold by peptide recognition. Insights into the thioredoxin folding mechanism. Biochemistry 2009; 48:595-607. [PMID: 19119857 DOI: 10.1021/bi801969w] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Thioredoxins (TRXs) are monomeric alpha/beta proteins with a fold characterized by a central twisted beta-sheet surrounded by alpha-helical elements. The interaction of the C-terminal alpha-helix 5 of TRX against the remainder of the protein involves a close packing of hydrophobic surfaces, offering the opportunity of studying a fine-tuned molecular recognition phenomenon with long-range consequences on the acquisition of tertiary structure. In this work, we focus on the significance of interactions involving residues L94, L99, E101, F102, L103 and L107 on the formation of the noncovalent complex between reduced TRX1-93 and TRX94-108. The conformational status of the system was assessed experimentally by circular dichroism, intrinsic fluorescence emission and enzymic activity; and theoretically by molecular dynamics simulations (MDS). Alterations in tertiary structure of the complexes, resulting as a consequence of site specific mutation, were also examined. To distinguish the effect of alanine scanning mutagenesis on secondary structure stability, the intrinsic helix-forming ability of the mutant peptides was monitored experimentally by far-UV CD spectroscopy upon the addition of 2,2,2-trifluoroethanol, and also theoretically by Monte Carlo conformational search and MDS. This evidence suggests a key role of residues L99, F102 and L103 on the stabilization of the secondary structure of alpha-helix 5, and on the acquisition of tertiary structure upon complex formation. We hypothesize that the transition between a partially folded and a native-like conformation of reduced TRX1-93 would fundamentally depend on the consolidation of a cooperative tertiary unit based on the interaction between alpha-helix 3 and alpha-helix 5.
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Affiliation(s)
- Javier Santos
- Department of Biological Chemistry and Institute of Biochemistry and Biophysics (IQUIFIB), School of Pharmacy and Biochemistry, University of Buenos Aires, Junín 956, C1113AAD, Buenos Aires, Argentina
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13
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Bjelić S, Jelesarov I. A survey of the year 2007 literature on applications of isothermal titration calorimetry. J Mol Recognit 2008; 21:289-312. [PMID: 18729242 DOI: 10.1002/jmr.909] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Elucidation of the energetic principles of binding affinity and specificity is a central task in many branches of current sciences: biology, medicine, pharmacology, chemistry, material sciences, etc. In biomedical research, integral approaches combining structural information with in-solution biophysical data have proved to be a powerful way toward understanding the physical basis of vital cellular phenomena. Isothermal titration calorimetry (ITC) is a valuable experimental tool facilitating quantification of the thermodynamic parameters that characterize recognition processes involving biomacromolecules. The method provides access to all relevant thermodynamic information by performing a few experiments. In particular, ITC experiments allow to by-pass tedious and (rarely precise) procedures aimed at determining the changes in enthalpy and entropy upon binding by van't Hoff analysis. Notwithstanding limitations, ITC has now the reputation of being the "gold standard" and ITC data are widely used to validate theoretical predictions of thermodynamic parameters, as well as to benchmark the results of novel binding assays. In this paper, we discuss several publications from 2007 reporting ITC results. The focus is on applications in biologically oriented fields. We do not intend a comprehensive coverage of all newly accumulated information. Rather, we emphasize work which has captured our attention with originality and far-reaching analysis, or else has provided ideas for expanding the potential of the method.
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Affiliation(s)
- Sasa Bjelić
- Biochemisches Institut der Universität Zürich, Winterthurerstrasse 190, Zürich, Switzerland
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14
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Manta B, Hugo M, Ortiz C, Ferrer-Sueta G, Trujillo M, Denicola A. The peroxidase and peroxynitrite reductase activity of human erythrocyte peroxiredoxin 2. Arch Biochem Biophys 2008; 484:146-54. [PMID: 19061854 DOI: 10.1016/j.abb.2008.11.017] [Citation(s) in RCA: 161] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2008] [Revised: 11/14/2008] [Accepted: 11/15/2008] [Indexed: 12/12/2022]
Abstract
Peroxiredoxin 2 (Prx2) is a 2-Cys peroxiredoxin extremely abundant in the erythrocyte. The peroxidase activity was studied in a steady-state approach yielding an apparent K(M) of 2.4 microM for human thioredoxin and a very low K(M) for H2O2 (0.7 microM). Rate constants for the reaction of peroxidatic cysteine with the peroxide substrate, H2O2 or peroxynitrite, were determined by competition kinetics, k(2) = 1.0 x 10(8) and 1.4 x 10(7) M(-1) s(-1) at 25 degrees C and pH 7.4, respectively. Excess of both oxidants inactivated the enzyme by overoxidation and also tyrosine nitration and dityrosine were observed with peroxynitrite treatment. Prx2 associates into decamers (5 homodimers) and we estimated a dissociation constant K(d) < 10(-23) M(4) which confirms the enzyme exists as a decamer in vivo. Our kinetic results indicate Prx2 is a key antioxidant enzyme for the erythrocyte and reveal red blood cells as active oxidant scrubbers in the bloodstream.
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Affiliation(s)
- Bruno Manta
- Laboratorio de Fisicoquímica Biológica, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay
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