1
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Oda M. Analysis of the Structural Dynamics of Proteins in the Ligand-Unbound and -Bound States by Diffracted X-ray Tracking. Int J Mol Sci 2023; 24:13717. [PMID: 37762021 PMCID: PMC10531450 DOI: 10.3390/ijms241813717] [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: 08/17/2023] [Revised: 09/03/2023] [Accepted: 09/05/2023] [Indexed: 09/29/2023] Open
Abstract
Although many protein structures have been determined at atomic resolution, the majority of them are static and represent only the most stable or averaged structures in solution. When a protein binds to its ligand, it usually undergoes fluctuation and changes its conformation. One attractive method for obtaining an accurate view of proteins in solution, which is required for applications such as the rational design of proteins and structure-based drug design, is diffracted X-ray tracking (DXT). DXT can detect the protein structural dynamics on a timeline via gold nanocrystals attached to the protein. Here, the structure dynamics of single-chain Fv antibodies, helix bundle-forming de novo designed proteins, and DNA-binding proteins in both ligand-unbound and ligand-bound states were analyzed using the DXT method. The resultant mean square angular displacements (MSD) curves in both the tilting and twisting directions clearly demonstrated that structural fluctuations were suppressed upon ligand binding, and the binding energies determined using the angular diffusion coefficients from the MSD agreed well with the binding thermodynamics determined using isothermal titration calorimetry. In addition, the size of gold nanocrystals is discussed, which is one of the technical concerns of DXT.
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Affiliation(s)
- Masayuki Oda
- Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, 1-5 Hangi-cho, Shimogamo, Sakyo-ku, Kyoto 606-8522, Japan
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2
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Pirro F, La Gatta S, Arrigoni F, Famulari A, Maglio O, Del Vecchio P, Chiesa M, De Gioia L, Bertini L, Chino M, Nastri F, Lombardi A. A De Novo-Designed Type 3 Copper Protein Tunes Catechol Substrate Recognition and Reactivity. Angew Chem Int Ed Engl 2023; 62:e202211552. [PMID: 36334012 DOI: 10.1002/anie.202211552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Indexed: 11/07/2022]
Abstract
De novo metalloprotein design is a remarkable approach to shape protein scaffolds toward specific functions. Here, we report the design and characterization of Due Rame 1 (DR1), a de novo designed protein housing a di-copper site and mimicking the Type 3 (T3) copper-containing polyphenol oxidases (PPOs). To achieve this goal, we hierarchically designed the first and the second di-metal coordination spheres to engineer the di-copper site into a simple four-helix bundle scaffold. Spectroscopic, thermodynamic, and functional characterization revealed that DR1 recapitulates the T3 copper site, supporting different copper redox states, and being active in the O2 -dependent oxidation of catechols to o-quinones. Careful design of the residues lining the substrate access site endows DR1 with substrate recognition, as revealed by Hammet analysis and computational studies on substituted catechols. This study represents a premier example in the construction of a functional T3 copper site into a designed four-helix bundle protein.
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Affiliation(s)
- Fabio Pirro
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia, 80126, Naples, Italy
| | - Salvatore La Gatta
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia, 80126, Naples, Italy
| | - Federica Arrigoni
- Department of Biotechnology and Biosciences, University of Milan-Bicocca, Piazza della Scienza 2, 20126, Milan, Italy
| | - Antonino Famulari
- Department of Chemistry, University of Torino, Via Giuria 9, 10125, Torino, Italy.,Department of Condensed Matter Physics, University of of Zaragoza, Calle Pedro Cerbuna 12, 50009, Zaragoza, Spain
| | - Ornella Maglio
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia, 80126, Naples, Italy.,Institute of Biostructures and Bioimaging (IBB), National Research Council (CNR), Via Pietro Castellino 111, 80131, Napoli, Italy
| | - Pompea Del Vecchio
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia, 80126, Naples, Italy
| | - Mario Chiesa
- Department of Chemistry, University of Torino, Via Giuria 9, 10125, Torino, Italy
| | - Luca De Gioia
- Department of Biotechnology and Biosciences, University of Milan-Bicocca, Piazza della Scienza 2, 20126, Milan, Italy
| | - Luca Bertini
- Department of Biotechnology and Biosciences, University of Milan-Bicocca, Piazza della Scienza 2, 20126, Milan, Italy
| | - Marco Chino
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia, 80126, Naples, Italy
| | - Flavia Nastri
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia, 80126, Naples, Italy
| | - Angela Lombardi
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia, 80126, Naples, Italy
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3
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Koebke KJ, Pinter TBJ, Pitts WC, Pecoraro VL. Catalysis and Electron Transfer in De Novo Designed Metalloproteins. Chem Rev 2022; 122:12046-12109. [PMID: 35763791 PMCID: PMC10735231 DOI: 10.1021/acs.chemrev.1c01025] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
One of the hallmark advances in our understanding of metalloprotein function is showcased in our ability to design new, non-native, catalytically active protein scaffolds. This review highlights progress and milestone achievements in the field of de novo metalloprotein design focused on reports from the past decade with special emphasis on de novo designs couched within common subfields of bioinorganic study: heme binding proteins, monometal- and dimetal-containing catalytic sites, and metal-containing electron transfer sites. Within each subfield, we highlight several of what we have identified as significant and important contributions to either our understanding of that subfield or de novo metalloprotein design as a discipline. These reports are placed in context both historically and scientifically. General suggestions for future directions that we feel will be important to advance our understanding or accelerate discovery are discussed.
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Affiliation(s)
- Karl J. Koebke
- Department of Chemistry, University of Michigan Ann Arbor, MI 48109 USA
| | | | - Winston C. Pitts
- Department of Chemistry, University of Michigan Ann Arbor, MI 48109 USA
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4
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Van Stappen C, Deng Y, Liu Y, Heidari H, Wang JX, Zhou Y, Ledray AP, Lu Y. Designing Artificial Metalloenzymes by Tuning of the Environment beyond the Primary Coordination Sphere. Chem Rev 2022; 122:11974-12045. [PMID: 35816578 DOI: 10.1021/acs.chemrev.2c00106] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Metalloenzymes catalyze a variety of reactions using a limited number of natural amino acids and metallocofactors. Therefore, the environment beyond the primary coordination sphere must play an important role in both conferring and tuning their phenomenal catalytic properties, enabling active sites with otherwise similar primary coordination environments to perform a diverse array of biological functions. However, since the interactions beyond the primary coordination sphere are numerous and weak, it has been difficult to pinpoint structural features responsible for the tuning of activities of native enzymes. Designing artificial metalloenzymes (ArMs) offers an excellent basis to elucidate the roles of these interactions and to further develop practical biological catalysts. In this review, we highlight how the secondary coordination spheres of ArMs influence metal binding and catalysis, with particular focus on the use of native protein scaffolds as templates for the design of ArMs by either rational design aided by computational modeling, directed evolution, or a combination of both approaches. In describing successes in designing heme, nonheme Fe, and Cu metalloenzymes, heteronuclear metalloenzymes containing heme, and those ArMs containing other metal centers (including those with non-native metal ions and metallocofactors), we have summarized insights gained on how careful controls of the interactions in the secondary coordination sphere, including hydrophobic and hydrogen bonding interactions, allow the generation and tuning of these respective systems to approach, rival, and, in a few cases, exceed those of native enzymes. We have also provided an outlook on the remaining challenges in the field and future directions that will allow for a deeper understanding of the secondary coordination sphere a deeper understanding of the secondary coordintion sphere to be gained, and in turn to guide the design of a broader and more efficient variety of ArMs.
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Affiliation(s)
- Casey Van Stappen
- Department of Chemistry, University of Texas at Austin, 105 East 24th Street, Austin, Texas 78712, United States
| | - Yunling Deng
- Department of Chemistry, University of Texas at Austin, 105 East 24th Street, Austin, Texas 78712, United States
| | - Yiwei Liu
- Department of Chemistry, University of Illinois, Urbana-Champaign, 505 South Mathews Avenue, Urbana, Illinois 61801, United States
| | - Hirbod Heidari
- Department of Chemistry, University of Texas at Austin, 105 East 24th Street, Austin, Texas 78712, United States
| | - Jing-Xiang Wang
- Department of Chemistry, University of Texas at Austin, 105 East 24th Street, Austin, Texas 78712, United States
| | - Yu Zhou
- Department of Chemistry, University of Texas at Austin, 105 East 24th Street, Austin, Texas 78712, United States
| | - Aaron P Ledray
- Department of Chemistry, University of Texas at Austin, 105 East 24th Street, Austin, Texas 78712, United States
| | - Yi Lu
- Department of Chemistry, University of Texas at Austin, 105 East 24th Street, Austin, Texas 78712, United States.,Department of Chemistry, University of Illinois, Urbana-Champaign, 505 South Mathews Avenue, Urbana, Illinois 61801, United States
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5
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Abstract
Natural metalloproteins perform many functions - ranging from sensing to electron transfer and catalysis - in which the position and property of each ligand and metal, is dictated by protein structure. De novo protein design aims to define an amino acid sequence that encodes a specific structure and function, providing a critical test of the hypothetical inner workings of (metallo)proteins. To date, de novo metalloproteins have used simple, symmetric tertiary structures - uncomplicated by the large size and evolutionary marks of natural proteins - to interrogate structure-function hypotheses. In this Review, we discuss de novo design applications, such as proteins that induce complex, increasingly asymmetric ligand geometries to achieve function, as well as the use of more canonical ligand geometries to achieve stability. De novo design has been used to explore how proteins fine-tune redox potentials and catalyse both oxidative and hydrolytic reactions. With an increased understanding of structure-function relationships, functional proteins including O2-dependent oxidases, fast hydrolases, and multi-proton/multi-electron reductases, have been created. In addition, proteins can now be designed using xeno-biological metals or cofactors and principles from inorganic chemistry to derive new-to-nature functions. These results and the advances in computational protein design suggest a bright future for the de novo design of diverse, functional metalloproteins.
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Affiliation(s)
- Matthew J. Chalkley
- Department of Pharmaceutical Chemistry and the Cardiovascular Research Institute, University of California at San Francisco, San Francisco, (CA), USA
| | - Samuel I. Mann
- Department of Pharmaceutical Chemistry and the Cardiovascular Research Institute, University of California at San Francisco, San Francisco, (CA), USA
| | - William F. DeGrado
- Department of Pharmaceutical Chemistry and the Cardiovascular Research Institute, University of California at San Francisco, San Francisco, (CA), USA
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6
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Vilbert AC, Liu Y, Dai H, Lu Y. Recent advances in tuning redox properties of electron transfer centers in metalloenzymes catalyzing oxygen reduction reaction and H 2 oxidation important for fuel cells design. CURRENT OPINION IN ELECTROCHEMISTRY 2021; 30:100780. [PMID: 34435160 PMCID: PMC8382256 DOI: 10.1016/j.coelec.2021.100780] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Current fuel-cell catalysts for oxygen reduction reaction (ORR) and H2 oxidation use precious metals and, for ORR, require high overpotentials. In contrast, metalloenzymes perform their respective reaction at low overpotentials using earth-abundant metals, making metalloenzymes ideal candidates for inspiring electrocatalytic design. Critical to the success of these enzymes are redox-active metal centers surrounding the enzyme active sites that ensure fast electron transfer (ET) to or away from the active site, by tuning the catalytic potential of the reaction as observed in multicopper oxidases but also in dictating the catalytic bias of the reaction as realized in hydrogenases. This review summarizes recent advances in studying these ET centers in multicopper oxidases and heme-copper oxidases that perform ORR and hydrogenases in carrying out H2 oxidation. Insights gained from understanding how the reduction potential of the ET centers effects reactivity at the active site in both the enzymes and their models are provided.
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Affiliation(s)
| | - Yiwei Liu
- Department of Chemistry and Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Huiguang Dai
- Department of Chemistry and Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Yi Lu
- Pacific Northwest National Laboratory, Richland, WA 99352, USA
- Department of Chemistry and Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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7
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Jung SM, Lee J, Song WJ. Design of artificial metalloenzymes with multiple inorganic elements: The more the merrier. J Inorg Biochem 2021; 223:111552. [PMID: 34332336 DOI: 10.1016/j.jinorgbio.2021.111552] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Revised: 06/21/2021] [Accepted: 07/15/2021] [Indexed: 11/27/2022]
Abstract
A large fraction of metalloenzymes harbors multiple metal-centers that are electronically and/or functionally arranged within their proteinaceous environments. To explore the orchestration of inorganic and biochemical components and to develop bioinorganic catalysts and materials, we have described selected examples of artificial metalloproteins having multiple metallocofactors that were grouped depending on their initial protein scaffolds, the nature of introduced inorganic moieties, and the method used to propagate the number of metal ions within a protein. They demonstrated that diverse inorganic moieties can be selectively grafted and modulated in protein environments, providing a retrosynthetic bottom-up approach in the design of versatile and proficient biocatalysts and biomimetic model systems to explore fundamental questions in bioinorganic chemistry.
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Affiliation(s)
- Se-Min Jung
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Jaehee Lee
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Woon Ju Song
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 08826, Republic of Korea.
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8
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Mirts EN, Dikanov SA, Jose A, Solomon EI, Lu Y. A Binuclear Cu A Center Designed in an All α-Helical Protein Scaffold. J Am Chem Soc 2020; 142:13779-13794. [PMID: 32662996 DOI: 10.1021/jacs.0c04226] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The primary and secondary coordination spheres of metal binding sites in metalloproteins have been investigated extensively, leading to the creation of high-performing functional metalloproteins; however, the impact of the overall structure of the protein scaffold on the unique properties of metalloproteins has rarely been studied. A primary example is the binuclear CuA center, an electron transfer cupredoxin domain of photosynthetic and respiratory complexes and, recently, a protein coregulated with particulate methane and ammonia monooxygenases. The redox potential, Cu-Cu spectroscopic features, and a valence delocalized state of CuA are difficult to reproduce in synthetic models, and every artificial protein CuA center to-date has used a modified cupredoxin. Here, we present a fully functional CuA center designed in a structurally nonhomologous protein, cytochrome c peroxidase (CcP), by only two mutations (CuACcP). We demonstrate with UV-visible absorption, resonance Raman, and magnetic circular dichroism spectroscopy that CuACcP is valence delocalized. Continuous wave and pulsed (HYSCORE) X-band EPR show it has a highly compact gz area and small Az hyperfine principal value with g and A tensors that resemble axially perturbed CuA. Stopped-flow kinetics found that CuA formation proceeds through a single T2Cu intermediate. The reduction potential of CuACcP is comparable to native CuA and can transfer electrons to a physiological redox partner. We built a structural model of the designed Cu binding site from extended X-ray absorption fine structure spectroscopy and validated it by mutation of coordinating Cys and His residues, revealing that a triad of residues (R48C, W51C, and His52) rigidly arranged on one α-helix is responsible for chelating the first Cu(II) and that His175 stabilizes the binuclear complex by rearrangement of the CcP heme-coordinating helix. This design is a demonstration that a highly conserved protein fold is not uniquely necessary to induce certain characteristic physical and chemical properties in a metal redox center.
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Affiliation(s)
- Evan N Mirts
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Sergei A Dikanov
- Department of Veterinary Clinical Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Anex Jose
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Edward I Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Yi Lu
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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9
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Jeong WJ, Yu J, Song WJ. Proteins as diverse, efficient, and evolvable scaffolds for artificial metalloenzymes. Chem Commun (Camb) 2020; 56:9586-9599. [DOI: 10.1039/d0cc03137b] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
We have extracted and categorized the desirable properties of proteins that are adapted as the scaffolds for artificial metalloenzymes.
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Affiliation(s)
- Woo Jae Jeong
- Department of Chemistry
- Seoul National University
- Seoul 08826
- Republic of Korea
| | - Jaeseung Yu
- Department of Chemistry
- Seoul National University
- Seoul 08826
- Republic of Korea
| | - Woon Ju Song
- Department of Chemistry
- Seoul National University
- Seoul 08826
- Republic of Korea
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10
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Engineering Metalloprotein Functions in Designed and Native Scaffolds. Trends Biochem Sci 2019; 44:1022-1040. [DOI: 10.1016/j.tibs.2019.06.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 06/05/2019] [Accepted: 06/11/2019] [Indexed: 12/15/2022]
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11
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Boyle AL, Rabe M, Crone NSA, Rhys GG, Soler N, Voskamp P, Pannu NS, Kros A. Selective coordination of three transition metal ions within a coiled-coil peptide scaffold. Chem Sci 2019; 10:7456-7465. [PMID: 31489168 PMCID: PMC6713864 DOI: 10.1039/c9sc01165j] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Accepted: 06/19/2019] [Indexed: 12/13/2022] Open
Abstract
Designing peptides that fold and assemble in response to metal ions tests our understanding of how peptide folding and metal binding influence one another. Here, histidine residues are introduced into the hydrophobic core of a coiled-coil trimer, generating a peptide that self-assembles upon the addition of metal ions. HisAD, the resulting peptide, is unstructured in the absence of metal and folds selectively to form an α-helical construct upon complexation with Cu(ii) and Ni(ii) but not Co(ii) or Zn(ii). The structure, and metal-binding ability, of HisAD is probed using a combination of circular dichroism (CD) spectroscopy, analytical ultracentrifugation (AUC), nuclear magnetic resonance (NMR) spectroscopy and X-ray crystallography. These show the peptide is trimeric and binds to both Cu(ii) and Ni(ii) in a 1 : 1 ratio with the histidine residues involved in the metal coordination, as designed. The X-ray crystal structure of the HisAD-Cu(ii) complex reveals the trimeric HisAD peptide coordinates three Cu(ii) ions; this is the first example of such a structure. Additionally, HisAD demonstrates an unprecedented discrimination between transition metal ions, the basis of which is likely to be related to the stability of the peptide-metal complexes formed.
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Affiliation(s)
- Aimee L Boyle
- Leiden Institute of Chemistry , Leiden University , Einsteinweg 55 , 2333 CC Leiden , The Netherlands .
| | - Martin Rabe
- Max-Planck-Institut für Eisenforschung GmbH , Max-Planck-Straße 1 , 40237 Düsseldorf , Germany
| | - Niek S A Crone
- Leiden Institute of Chemistry , Leiden University , Einsteinweg 55 , 2333 CC Leiden , The Netherlands .
| | - Guto G Rhys
- School of Chemistry , University of Bristol , Cantock's Close , Bristol , BS8 1TS , UK
| | - Nicolas Soler
- Structural Biology Unit , Institute of Molecular Biology of Barcelona (IBMB-CSIC) , Baldiri Reixac 15 , 08028 Barcelona , Spain
| | - Patrick Voskamp
- Leiden Institute of Chemistry , Leiden University , Einsteinweg 55 , 2333 CC Leiden , The Netherlands .
| | - Navraj S Pannu
- Leiden Institute of Chemistry , Leiden University , Einsteinweg 55 , 2333 CC Leiden , The Netherlands .
| | - Alexander Kros
- Leiden Institute of Chemistry , Leiden University , Einsteinweg 55 , 2333 CC Leiden , The Netherlands .
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12
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Ross MO, Fisher OS, Morgada MN, Krzyaniak MD, Wasielewski MR, Vila AJ, Hoffman BM, Rosenzweig AC. Formation and Electronic Structure of an Atypical Cu A Site. J Am Chem Soc 2019; 141:4678-4686. [PMID: 30807125 PMCID: PMC6953997 DOI: 10.1021/jacs.8b13610] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PmoD, a recently discovered protein from methane-oxidizing bacteria, forms a homodimer with a dicopper CuA center at the dimer interface. Although the optical and electron paramagnetic resonance (EPR) spectroscopic signatures of the PmoD CuA bear similarities to those of canonical CuA sites, there are also some puzzling differences. Here we have characterized the rapid formation (seconds) and slow decay (hours) of this homodimeric CuA site to two mononuclear Cu2+ sites, as well as its electronic and geometric structure, using stopped-flow optical and advanced paramagnetic resonance spectroscopies. PmoD CuA formation occurs rapidly and involves a short-lived intermediate with a λmax of 360 nm. Unlike other CuA sites, the PmoD CuA is unstable, decaying to two type 2 Cu2+ centers. Surprisingly, NMR data indicate that the PmoD CuA has a pure σu* ground state rather than the typical equilibrium between σu* and πu of all other CuA proteins. EPR, ENDOR, ESEEM, and HYSCORE data indicate the presence of two histidine and two cysteine ligands coordinating the CuA core in a highly symmetrical fashion. This report significantly expands the diversity and understanding of known CuA sites.
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Affiliation(s)
- Matthew O. Ross
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
- Department of Chemistry, Northwestern University, Evanston, IL, USA
| | - Oriana S. Fisher
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
- Department of Chemistry, Northwestern University, Evanston, IL, USA
| | - Marcos N. Morgada
- Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET-UNR), Ocampo y Esmeralda, S2002LRK Rosario, Argentina
- Área Biofísica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, S2002LRK Rosario, Argentina
| | - Matthew D. Krzyaniak
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA
| | - Michael R. Wasielewski
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA
| | - Alejandro J. Vila
- Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET-UNR), Ocampo y Esmeralda, S2002LRK Rosario, Argentina
| | - Brian M. Hoffman
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
- Department of Chemistry, Northwestern University, Evanston, IL, USA
| | - Amy C. Rosenzweig
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
- Department of Chemistry, Northwestern University, Evanston, IL, USA
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13
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Koebke KJ, Ruckthong L, Meagher JL, Mathieu E, Harland J, Deb A, Lehnert N, Policar C, Tard C, Penner-Hahn JE, Stuckey JA, Pecoraro VL. Clarifying the Copper Coordination Environment in a de Novo Designed Red Copper Protein. Inorg Chem 2018; 57:12291-12302. [PMID: 30226758 PMCID: PMC6183058 DOI: 10.1021/acs.inorgchem.8b01989] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cupredoxins are copper-dependent electron-transfer proteins that can be categorized as blue, purple, green, and red depending on the spectroscopic properties of the Cu(II) bound forms. Interestingly, despite significantly different first coordination spheres and nuclearity, all cupredoxins share a common Greek Key β-sheet fold. We have previously reported the design of a red copper protein within a completely distinct three-helical bundle protein, α3DChC2. (1) While this design demonstrated that a β-barrel fold was not requisite to recapitulate the properties of a native cupredoxin center, the parent peptide α3D was not sufficiently stable to allow further study through additional mutations. Here we present the design of an elongated protein GRANDα3D (GRα3D) with Δ Gu = -11.4 kcal/mol compared to the original design's -5.1 kcal/mol. Diffraction quality crystals were grown of GRα3D (a first for an α3D peptide) and solved to a resolution of 1.34 Å. Examination of this structure suggested that Glu41 might interact with the Cu in our previously reported red copper protein. The previous bis(histidine)(cysteine) site (GRα3DChC2) was designed into this new scaffold and a series of variant constructs were made to explore this hypothesis. Mutation studies around Glu41 not only prove the proposed interaction, but also enabled tuning of the constructs' hyperfine coupling constant from 160 to 127 × 10-4 cm-1. X-ray absorption spectroscopy analysis is consistent with these hyperfine coupling differences being the result of variant 4p mixing related to coordination geometry changes. These studies not only prove that an Glu41-Cu interaction leads to the α3DChC2 construct's red copper protein like spectral properties, but also exemplify the exact control one can have in a de novo construct to tune the properties of an electron-transfer Cu site.
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Affiliation(s)
- Karl J. Koebke
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Leela Ruckthong
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Jennifer L. Meagher
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Emilie Mathieu
- Laboratoire des biomolécules, LBM, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - Jill Harland
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Aniruddha Deb
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Nicolai Lehnert
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Clotilde Policar
- Laboratoire des biomolécules, LBM, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - Cédric Tard
- LCM, CNRS, Ecole Polytechnique, Université Paris-Saclay, 91128 Palaiseau Cedex, France
| | - James E. Penner-Hahn
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Jeanne A. Stuckey
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Vincent L. Pecoraro
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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Chino M, Zhang SQ, Pirro F, Leone L, Maglio O, Lombardi A, DeGrado WF. Spectroscopic and metal binding properties of a de novo metalloprotein binding a tetrazinc cluster. Biopolymers 2018; 109:e23339. [PMID: 30203532 PMCID: PMC6218314 DOI: 10.1002/bip.23229] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 05/18/2018] [Accepted: 05/22/2018] [Indexed: 12/27/2022]
Abstract
De novo design provides an attractive approach, which allows one to test and refine the principles guiding metalloproteins in defining the geometry and reactivity of their metal ion cofactors. Although impressive progress has been made in designing proteins that bind transition metal ions including iron-sulfur clusters, the design of tetranuclear clusters with oxygen-rich environments remains in its infancy. In previous work, we described the design of homotetrameric four-helix bundles that bind tetra-Zn2+ clusters. The crystal structures of the helical proteins were in good agreement with the overall design, and the metal-binding and conformational properties of the helical bundles in solution were consistent with the crystal structures. However, the corresponding apo-proteins were not fully folded in solution. In this work, we design three peptides, based on the crystal structure of the original bundles. One of the peptides forms tetramers in aqueous solution in the absence of metal ions as assessed by CD and NMR. It also binds Zn2+ in the intended stoichiometry. These studies strongly suggest that the desired structure has been achieved in the apo state, providing evidence that the peptide is able to actively impart the designed geometry to the metal cluster.
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Affiliation(s)
- Marco Chino
- Department of Chemical Sciences, University of Napoli “Federico II”, Via Cintia, 46, 80126 Napoli, Italy
| | - Shao-Qing Zhang
- Department of Pharmaceutical Chemistry and the Cardiovascular Research Institute, University of California at San Francisco, San Francisco, CA 94158-9001, United States
- Department of Chemistry, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104-6396, United States
| | - Fabio Pirro
- Department of Chemical Sciences, University of Napoli “Federico II”, Via Cintia, 46, 80126 Napoli, Italy
| | - Linda Leone
- Department of Chemical Sciences, University of Napoli “Federico II”, Via Cintia, 46, 80126 Napoli, Italy
| | - Ornella Maglio
- Department of Chemical Sciences, University of Napoli “Federico II”, Via Cintia, 46, 80126 Napoli, Italy
- Institute of Biostructure and Bioimaging, National Research Council, via Mezzocannone, 16, 80134, Napoli, Italy
| | - Angela Lombardi
- Department of Chemical Sciences, University of Napoli “Federico II”, Via Cintia, 46, 80126 Napoli, Italy
| | - William F. DeGrado
- Department of Pharmaceutical Chemistry and the Cardiovascular Research Institute, University of California at San Francisco, San Francisco, CA 94158-9001, United States
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15
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Zhang SQ, Chino M, Liu L, Tang Y, Hu X, DeGrado WF, Lombardi A. De Novo Design of Tetranuclear Transition Metal Clusters Stabilized by Hydrogen-Bonded Networks in Helical Bundles. J Am Chem Soc 2018; 140:1294-1304. [PMID: 29249157 PMCID: PMC5860638 DOI: 10.1021/jacs.7b08261] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
De novo design provides an attractive approach to test the mechanism by which metalloproteins define the geometry and reactivity of their metal ion cofactors. While there has been considerable progress in designing proteins that bind transition metal ions including iron-sulfur clusters, the design of tetranuclear clusters with oxygen-rich environments has not been accomplished. Here, we describe the design of tetranuclear clusters, consisting of four Zn2+ and four carboxylate oxygens situated at the vertices of a distorted cube-like structure. The tetra-Zn2+ clusters are bound at a buried site within a four-helix bundle, with each helix donating a single carboxylate (Glu or Asp) and imidazole (His) ligand, as well as second- and third-shell ligands. Overall, the designed site consists of four Zn2+ and 16 polar side chains in a fully connected hydrogen-bonded network. The designed proteins have apolar cores at the top and bottom of the bundle, which drive the assembly of the liganding residues near the center of the bundle. The steric bulk of the apolar residues surrounding the binding site was varied to determine how subtle changes in helix-helix packing affect the binding site. The crystal structures of two of four proteins synthesized were in good agreement with the overall design; both formed a distorted cuboidal site stabilized by flanking second- and third-shell interactions that stabilize the primary ligands. A third structure bound a single Zn2+ in an unanticipated geometry, and the fourth bound multiple Zn2+ at multiple sites at partial occupancy. The metal-binding and conformational properties of the helical bundles in solution, probed by circular dichroism spectroscopy, analytical ultracentrifugation, and NMR, were consistent with the crystal structures.
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Affiliation(s)
- Shao-Qing Zhang
- Department of Chemistry, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104-6396, United States
- Department of Pharmaceutical Chemistry and the Cardiovascular Research Institute, University of California at San Francisco, San Francisco, CA 94158-9001, United States
| | - Marco Chino
- Department of Chemical Sciences, University of Napoli “Federico II”, Via Cintia, 46, I-80126 Napoli, Italy
| | - Lijun Liu
- Department of Pharmaceutical Chemistry and the Cardiovascular Research Institute, University of California at San Francisco, San Francisco, CA 94158-9001, United States
- DLX Scientific, Lawrence, KS 66049, United States
| | - Youzhi Tang
- Department of Pharmaceutical Chemistry and the Cardiovascular Research Institute, University of California at San Francisco, San Francisco, CA 94158-9001, United States
- College of Veterinary Medicine, South China Agricultural University, Guangdong 510642, China
| | - Xiaozhen Hu
- Department of Pharmaceutical Chemistry and the Cardiovascular Research Institute, University of California at San Francisco, San Francisco, CA 94158-9001, United States
| | - William F. DeGrado
- Department of Pharmaceutical Chemistry and the Cardiovascular Research Institute, University of California at San Francisco, San Francisco, CA 94158-9001, United States
| | - Angela Lombardi
- Department of Chemical Sciences, University of Napoli “Federico II”, Via Cintia, 46, I-80126 Napoli, Italy
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17
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Computational approaches for de novo design and redesign of metal-binding sites on proteins. Biosci Rep 2017; 37:BSR20160179. [PMID: 28167677 PMCID: PMC5482196 DOI: 10.1042/bsr20160179] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 02/06/2017] [Accepted: 02/06/2017] [Indexed: 12/25/2022] Open
Abstract
Metal ions play pivotal roles in protein structure, function and stability. The functional and structural diversity of proteins in nature expanded with the incorporation of metal ions or clusters in proteins. Approximately one-third of these proteins in the databases contain metal ions. Many biological and chemical processes in nature involve metal ion-binding proteins, aka metalloproteins. Many cellular reactions that underpin life require metalloproteins. Most of the remarkable, complex chemical transformations are catalysed by metalloenzymes. Realization of the importance of metal-binding sites in a variety of cellular events led to the advancement of various computational methods for their prediction and characterization. Furthermore, as structural and functional knowledgebase about metalloproteins is expanding with advances in computational and experimental fields, the focus of the research is now shifting towards de novo design and redesign of metalloproteins to extend nature’s own diversity beyond its limits. In this review, we will focus on the computational toolbox for prediction of metal ion-binding sites, de novo metalloprotein design and redesign. We will also give examples of tailor-made artificial metalloproteins designed with the computational toolbox.
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18
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Dizicheh ZB, Halloran N, Asma W, Ghirlanda G. De Novo Design of Iron–Sulfur Proteins. Methods Enzymol 2017; 595:33-53. [DOI: 10.1016/bs.mie.2017.07.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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19
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Moser CC, Sheehan MM, Ennist NM, Kodali G, Bialas C, Englander MT, Discher BM, Dutton PL. De Novo Construction of Redox Active Proteins. Methods Enzymol 2016; 580:365-88. [PMID: 27586341 DOI: 10.1016/bs.mie.2016.05.048] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Relatively simple principles can be used to plan and construct de novo proteins that bind redox cofactors and participate in a range of electron-transfer reactions analogous to those seen in natural oxidoreductase proteins. These designed redox proteins are called maquettes. Hydrophobic/hydrophilic binary patterning of heptad repeats of amino acids linked together in a single-chain self-assemble into 4-alpha-helix bundles. These bundles form a robust and adaptable frame for uncovering the default properties of protein embedded cofactors independent of the complexities introduced by generations of natural selection and allow us to better understand what factors can be exploited by man or nature to manipulate the physical chemical properties of these cofactors. Anchoring of redox cofactors such as hemes, light active tetrapyrroles, FeS clusters, and flavins by His and Cys residues allow cofactors to be placed at positions in which electron-tunneling rates between cofactors within or between proteins can be predicted in advance. The modularity of heptad repeat designs facilitates the construction of electron-transfer chains and novel combinations of redox cofactors and new redox cofactor assisted functions. Developing de novo designs that can support cofactor incorporation upon expression in a cell is needed to support a synthetic biology advance that integrates with natural bioenergetic pathways.
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Affiliation(s)
- C C Moser
- University of Pennsylvania, Philadelphia, PA, United States
| | - M M Sheehan
- University of Pennsylvania, Philadelphia, PA, United States
| | - N M Ennist
- University of Pennsylvania, Philadelphia, PA, United States
| | - G Kodali
- University of Pennsylvania, Philadelphia, PA, United States
| | - C Bialas
- University of Pennsylvania, Philadelphia, PA, United States
| | - M T Englander
- University of Pennsylvania, Philadelphia, PA, United States
| | - B M Discher
- University of Pennsylvania, Philadelphia, PA, United States
| | - P L Dutton
- University of Pennsylvania, Philadelphia, PA, United States.
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20
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Hosseinzadeh P, Lu Y. Design and fine-tuning redox potentials of metalloproteins involved in electron transfer in bioenergetics. BIOCHIMICA ET BIOPHYSICA ACTA 2016; 1857:557-581. [PMID: 26301482 PMCID: PMC4761536 DOI: 10.1016/j.bbabio.2015.08.006] [Citation(s) in RCA: 114] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Accepted: 08/20/2015] [Indexed: 12/25/2022]
Abstract
Redox potentials are a major contributor in controlling the electron transfer (ET) rates and thus regulating the ET processes in the bioenergetics. To maximize the efficiency of the ET process, one needs to master the art of tuning the redox potential, especially in metalloproteins, as they represent major classes of ET proteins. In this review, we first describe the importance of tuning the redox potential of ET centers and its role in regulating the ET in bioenergetic processes including photosynthesis and respiration. The main focus of this review is to summarize recent work in designing the ET centers, namely cupredoxins, cytochromes, and iron-sulfur proteins, and examples in design of protein networks involved these ET centers. We then discuss the factors that affect redox potentials of these ET centers including metal ion, the ligands to metal center and interactions beyond the primary ligand, especially non-covalent secondary coordination sphere interactions. We provide examples of strategies to fine-tune the redox potential using both natural and unnatural amino acids and native and nonnative cofactors. Several case studies are used to illustrate recent successes in this area. Outlooks for future endeavors are also provided. This article is part of a Special Issue entitled Biodesign for Bioenergetics--the design and engineering of electronic transfer cofactors, proteins and protein networks, edited by Ronald L. Koder and J.L. Ross Anderson.
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Affiliation(s)
- Parisa Hosseinzadeh
- Department of Chemistry and Department of Biochemistry, University of Illinois at Urbana-Champaign, 600 S. Mathews St., Urbana, IL, 61801, USA
| | - Yi Lu
- Department of Chemistry and Department of Biochemistry, University of Illinois at Urbana-Champaign, 600 S. Mathews St., Urbana, IL, 61801, USA.
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21
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Recent advances in designed coiled coils and helical bundles with inorganic prosthetic groups — from structural to functional applications. Curr Opin Chem Biol 2016; 31:160-5. [DOI: 10.1016/j.cbpa.2016.03.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 03/08/2016] [Accepted: 03/08/2016] [Indexed: 11/17/2022]
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22
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Yu F, Cangelosi VM, Zastrow ML, Tegoni M, Plegaria JS, Tebo AG, Mocny CS, Ruckthong L, Qayyum H, Pecoraro VL. Protein design: toward functional metalloenzymes. Chem Rev 2014; 114:3495-578. [PMID: 24661096 PMCID: PMC4300145 DOI: 10.1021/cr400458x] [Citation(s) in RCA: 340] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Fangting Yu
- University of Michigan, Ann Arbor, Michigan 48109, United States
| | | | | | | | | | - Alison G. Tebo
- University of Michigan, Ann Arbor, Michigan 48109, United States
| | | | - Leela Ruckthong
- University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Hira Qayyum
- University of Michigan, Ann Arbor, Michigan 48109, United States
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23
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24
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Incorporating metals into de novo proteins. Curr Opin Chem Biol 2013; 17:934-9. [DOI: 10.1016/j.cbpa.2013.10.015] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 10/07/2013] [Accepted: 10/08/2013] [Indexed: 11/24/2022]
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25
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Roy A, Sarrou I, Vaughn MD, Astashkin AV, Ghirlanda G. De Novo Design of an Artificial Bis[4Fe-4S] Binding Protein. Biochemistry 2013; 52:7586-94. [DOI: 10.1021/bi401199s] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anindya Roy
- Department
of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - Iosifina Sarrou
- Department
of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - Michael D. Vaughn
- Department
of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - Andrei V. Astashkin
- Department
of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Giovanna Ghirlanda
- Department
of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, United States
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26
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Zastrow ML, Pecoraro VL. Designing functional metalloproteins: from structural to catalytic metal sites. Coord Chem Rev 2013; 257:2565-2588. [PMID: 23997273 PMCID: PMC3756834 DOI: 10.1016/j.ccr.2013.02.007] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Metalloenzymes efficiently catalyze some of the most important and difficult reactions in nature. For many years, coordination chemists have effectively used small molecule models to understand these systems. More recently, protein design has been shown to be an effective approach for mimicking metal coordination environments. Since the first designed proteins were reported, much success has been seen for incorporating metal sites into proteins and attaining the desired coordination environment but until recently, this has been with a lack of significant catalytic activity. Now there are examples of designed metalloproteins that, although not yet reaching the activity of native enzymes, are considerably closer. In this review, we highlight work leading up to the design of a small metalloprotein containing two metal sites, one for structural stability (HgS3) and the other a separate catalytic zinc site to mimic carbonic anhydrase activity (ZnN3O). The first section will describe previous studies that allowed for a high affinity thiolate site that binds heavy metals in a way that stabilizes three-stranded coiled coils. The second section will examine ways of preparing histidine rich environments that lead to metal based hydrolytic catalysts. We will also discuss other recent examples of the design of structural metal sites and functional metalloenzymes. Our work demonstrates that attaining the proper first coordination geometry of a metal site can lead to a significant fraction of catalytic activity, apparently independent of the type of secondary structure of the surrounding protein environment. We are now in a position to begin to meet the challenge of building a metalloenzyme systematically from the bottom-up by engineering and analyzing interactions directly around the metal site and beyond.
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Affiliation(s)
- Melissa L. Zastrow
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
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27
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Designing a functional type 2 copper center that has nitrite reductase activity within α-helical coiled coils. Proc Natl Acad Sci U S A 2012; 109:21234-9. [PMID: 23236170 DOI: 10.1073/pnas.1212893110] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
One of the ultimate objectives of de novo protein design is to realize systems capable of catalyzing redox reactions on substrates. This goal is challenging as redox-active proteins require design considerations for both the reduced and oxidized states of the protein. In this paper, we describe the spectroscopic characterization and catalytic activity of a de novo designed metallopeptide Cu(I/II)(TRIL23H)(3)(+/2+), where Cu(I/II) is embeded in α-helical coiled coils, as a model for the Cu(T2) center of copper nitrite reductase. In Cu(I/II)(TRIL23H)(3)(+/2+), Cu(I) is coordinated to three histidines, as indicated by X-ray absorption data, and Cu(II) to three histidines and one or two water molecules. Both ions are bound in the interior of the three-stranded coiled coils with affinities that range from nano- to micromolar [Cu(II)], and picomolar [Cu(I)]. The Cu(His)(3) active site is characterized in both oxidation states, revealing similarities to the Cu(T2) site in the natural enzyme. The species Cu(II)(TRIL23H)(3)(2+) in aqueous solution can be reduced to Cu(I)(TRIL23H)(3)(+) using ascorbate, and reoxidized by nitrite with production of nitric oxide. At pH 5.8, with an excess of both the reductant (ascorbate) and the substrate (nitrite), the copper peptide Cu(II)(TRIL23H)(3)(2+) acts as a catalyst for the reduction of nitrite with at least five turnovers and no loss of catalytic efficiency after 3.7 h. The catalytic activity, which is first order in the concentration of the peptide, also shows a pH dependence that is described and discussed.
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