1
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Tran DK, West SM, Speck EMK, Jenekhe SA. Observation of super-Nernstian proton-coupled electron transfer and elucidation of nature of charge carriers in a multiredox conjugated polymer. Chem Sci 2024; 15:7623-7642. [PMID: 38784743 PMCID: PMC11110174 DOI: 10.1039/d4sc00785a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Accepted: 04/16/2024] [Indexed: 05/25/2024] Open
Abstract
Nernstian proton-coupled electron transfer (PCET) is a fundamental process central to many physical and biological systems, such as electrocatalysis, enzyme operation, DNA biosynthesis, pH-/bio-sensors, and electrochemical energy storage devices. We report herein the discovery of super-Nernstian PCET behavior with two protons per electron transferred in the electrochemical doping of a redox conjugated polymer, phenazine-substituted ladder poly(benzimidazobenzophenanthroline) (BBL-P), in aqueous electrolyte. We show that the super-Nernstian response originates from existence of multiredox centers that have a gradient of pKa on the conjugated polymer. Our use of various pH-dependent in operando techniques to probe the nature of charge carriers in n-doped BBL-P found that polarons are the charge carriers at low to intermediate levels of doping (0.1-1.0 electron per repeat unit (eru)) whereas at higher doing levels (1.3 eru), polarons, polaron pairs, and bipolarons co-exist, which evolve into strongly coupled polaron pairs at the highest doping levels (>1.5 eru). We show that PCET-assisted n-doping of BBL-P results in very high redox capacity (>1200 F cm-3) in acidic electrolyte. Our results provide important new insights into PCET in organic materials and the nature of charge carriers in n-doped conjugated polymers while having implications for various electrochemical devices.
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Affiliation(s)
- Duyen K Tran
- Department of Chemical Engineering, University of Washington Seattle Washington 98195-1750 USA
| | - Sarah M West
- Department of Chemistry, University of Washington Seattle Washington 98195-1750 USA
| | - Elizabeth M K Speck
- Department of Chemistry, University of Washington Seattle Washington 98195-1750 USA
| | - Samson A Jenekhe
- Department of Chemical Engineering, University of Washington Seattle Washington 98195-1750 USA
- Department of Chemistry, University of Washington Seattle Washington 98195-1750 USA
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2
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Kapuścińska K, Dukała Z, Doha M, Ansari E, Wang J, Brudvig GW, Brooks B, Amin M. Bridging the Coordination Chemistry of Small Compounds and Metalloproteins Using Machine Learning. J Chem Inf Model 2024; 64:2586-2593. [PMID: 38054243 DOI: 10.1021/acs.jcim.3c01564] [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: 12/07/2023]
Abstract
Metalloproteins require metal ions as cofactors to catalyze specific reactions with remarkable efficiency and specificity. In various electron transfer reactions, metals in the active sites change their oxidation states to facilitate the biochemical reactions. Cryogenic electron microscopy, X-ray, and X-ray free electron laser (XFEL) crystallography are used to image metalloproteins to understand the reaction mechanisms. However, radiation damage in cryoEM and X-ray crystallography, and the challenge of generating homogeneous crystals and keeping the appropriate experimental conditions for all the crystals in XFEL crystallography, may alter the oxidation states. Here, we build machine learning models trained on a large data set from the Cambridge Crystallographic Data Center to evaluate the metal oxidation states. The models yield high accuracy scores (from 82% to 94%) for all metals in the small molecules. Then, they were used to predict the oxidation states of more than 30 000 metal clusters in metalloproteins with Fe, Mn, Co, and Cu in their active sites. We found that most of the metals exist in the lower oxidation states (Fe2+ 77%, Mn2+ 85%, Co2+ 65%, and Cu+ 64%), and these populations correlate with the standard reduction potentials of the metal ions. Furthermore, we found no clear correlation between these populations and the resolution of the structures, which suggests no significant dependence of these predictions on the resolution. Our models represent a valuable tool for evaluating the oxidation states of the metals in metalloproteins imaged with different techniques. The data files and the machine learning code are available in a public GitHub repository: https://github.com/mamin03/OxitationStatesMetalloprotein.git.
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Affiliation(s)
- Katarzyna Kapuścińska
- Department of Sciences, University College Groningen, University of Groningen, 9718 BG Groningen, The Netherlands
| | - Zofia Dukała
- Department of Sciences, University College Groningen, University of Groningen, 9718 BG Groningen, The Netherlands
| | - Mekhola Doha
- Department of Sciences, University College Groningen, University of Groningen, 9718 BG Groningen, The Netherlands
| | - Eman Ansari
- Department of Sciences, University College Groningen, University of Groningen, 9718 BG Groningen, The Netherlands
| | - Jimin Wang
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Gary W Brudvig
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, United States
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Bernand Brooks
- Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Muhamed Amin
- Department of Sciences, University College Groningen, University of Groningen, 9718 BG Groningen, The Netherlands
- Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
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3
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Zeng R, Lv C, Wang C, Zhao G. Bionanomaterials based on protein self-assembly: Design and applications in biotechnology. Biotechnol Adv 2021; 52:107835. [PMID: 34520791 DOI: 10.1016/j.biotechadv.2021.107835] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 09/06/2021] [Accepted: 09/08/2021] [Indexed: 01/13/2023]
Abstract
Elegant protein assembly to generate new biomaterials undergoes extremely rapid development for wide extension of biotechnology applications, which can be a powerful tool not only for creating nanomaterials but also for advancing understanding of the structure of life. Unique biological properties of proteins bestow these artificial biomaterials diverse functions that can permit them to be applied in encapsulation, bioimaging, biocatalysis, biosensors, photosynthetic apparatus, electron transport, magnetogenetic applications, vaccine development and antibodies design. This review gives a perspective view of the latest advances in the construction of protein-based nanomaterials. We initially start with distinguishable, specific interactions to construct sundry nanomaterials through protein self-assembly and concisely expound the assembly mechanism from the design strategy. And then, the design and construction of 0D, 1D, 2D, 3D protein assembled nanomaterials are especially highlighted. Furthermore, the potential applications have been discussed in detail. Overall, this review will illustrate how to fabricate highly sophisticated nanomaterials oriented toward applications in biotechnology based on the rules of supramolecular chemistry.
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Affiliation(s)
- Ruiqi Zeng
- College of Food Science & Nutritional Engineering, China Agricultural University, Key Laboratory of Functional Dairy, Ministry of Education, Beijing 100083, China
| | - Chenyan Lv
- College of Food Science & Nutritional Engineering, China Agricultural University, Key Laboratory of Functional Dairy, Ministry of Education, Beijing 100083, China
| | - Chengtao Wang
- Beijing Engineering and Technology Research Center of Food Additives, Beijing Technology & Business University, No. 11 Fucheng Road, Haidian District, Beijing 100048, China
| | - Guanghua Zhao
- College of Food Science & Nutritional Engineering, China Agricultural University, Key Laboratory of Functional Dairy, Ministry of Education, Beijing 100083, China.
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4
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Márquez I, Olloqui-Sariego JL, Molero M, Andreu R, Roldán E, Calvente JJ. Active Role of the Buffer in the Proton-Coupled Electron Transfer of Immobilized Iron Porphyrins. Inorg Chem 2021; 60:42-54. [PMID: 32568550 DOI: 10.1021/acs.inorgchem.0c01091] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Evaluation of the proton-coupled electron transfer thermodynamics of immobilized hemin is challenging due to the disparity of its electrochemical titration curves reported in the literature. Deviations from the one-electron, one-proton transfer at circumneutral pHs have been commonly ascribed to either the formation of dimeric species or the ionization of a second iron-bound water molecule. Herein, however, we report on non-idealities in the more acidic region, whose onset and extent vary with the nature and concentration of the commonly used phosphate and acetate buffers. It is shown that these deviations originate in the ligand-exchange binding between the oxidized aquo-hemin complex and the anionic components of the buffer, so that they are restricted to the pH interval where these forms coexist. A stepwise approach was developed to quantify unambiguously the apparent and intrinsic binding equilibrium constants. The apparent binding equilibrium constant exhibits a peak-shaped pH dependence, whose maximum is located at approximately the midpoint between the pKa of the iron-bound water and the first pKa of the buffer, and its magnitude is greater for the phosphate than for the acetate buffer. But strikingly, the opposite trend was found for the magnitude of the intrinsic binding equilibrium constants determined from the apparent ones, due to the different relative locations of the phosphoric and acetic pKa values with respect to that of the oxidized aquo-hemin. To probe the role of the heme propionic residues, a similar study was carried out with a propionic-free iron porphyrin containing eight ethyl residues. These substituents decrease the acidity of the iron-bound water, strengthen the iron(III)-acetate binding, weaken the iron(III)-dihydrogen phosphate binding, and enable the binding between iron(III) and monohydrogen phosphate, which was hampered in hemin by the presence of the negatively charged propionate residues. Overall, this work provides a more complete speciation of immobilized iron porphyrins under acidic conditions than previously considered, showing the substitutional lability of the aqua ligand in the oxidized state of the iron center and the reluctance of its hydroxyl counterpart to anion exchange. Knowledge of these redox- and pH-dependent bindings with the buffer components is crucial for a rigorous quantification of the proton-coupled electron transfer and the electrocatalytic activity of iron porphyrins.
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Affiliation(s)
- Inmaculada Márquez
- Departamento de Quı́mica Fı́sica, Universidad de Sevilla, C/Profesor Garcı́a Conzález, 1, 41012 Sevilla, Spain
| | - José Luis Olloqui-Sariego
- Departamento de Quı́mica Fı́sica, Universidad de Sevilla, C/Profesor Garcı́a Conzález, 1, 41012 Sevilla, Spain
| | - Miguel Molero
- Departamento de Quı́mica Fı́sica, Universidad de Sevilla, C/Profesor Garcı́a Conzález, 1, 41012 Sevilla, Spain
| | - Rafael Andreu
- Departamento de Quı́mica Fı́sica, Universidad de Sevilla, C/Profesor Garcı́a Conzález, 1, 41012 Sevilla, Spain
| | - Emilio Roldán
- Departamento de Quı́mica Fı́sica, Universidad de Sevilla, C/Profesor Garcı́a Conzález, 1, 41012 Sevilla, Spain
| | - Juan José Calvente
- Departamento de Quı́mica Fı́sica, Universidad de Sevilla, C/Profesor Garcı́a Conzález, 1, 41012 Sevilla, Spain
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5
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Donegan RK, Moore CM, Hanna DA, Reddi AR. Handling heme: The mechanisms underlying the movement of heme within and between cells. Free Radic Biol Med 2019; 133:88-100. [PMID: 30092350 PMCID: PMC6363905 DOI: 10.1016/j.freeradbiomed.2018.08.005] [Citation(s) in RCA: 83] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Revised: 07/31/2018] [Accepted: 08/01/2018] [Indexed: 02/02/2023]
Abstract
Heme is an essential cofactor and signaling molecule required for virtually all aerobic life. However, excess heme is cytotoxic. Therefore, heme must be safely transported and trafficked from the site of synthesis in the mitochondria or uptake at the cell surface, to hemoproteins in most subcellular compartments. While heme synthesis and degradation are relatively well characterized, little is known about how heme is trafficked and transported throughout the cell. Herein, we review eukaryotic heme transport, trafficking, and mobilization, with a focus on factors that regulate bioavailable heme. We also highlight the role of gasotransmitters and small molecules in heme mobilization and bioavailability, and heme trafficking at the host-pathogen interface.
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Affiliation(s)
- Rebecca K Donegan
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, United States
| | - Courtney M Moore
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, United States
| | - David A Hanna
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, United States
| | - Amit R Reddi
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, United States; School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332, United States; Parker Petit Institute for Bioengineering & Biosciences, Georgia Institute of Technology, Atlanta, GA 30332, United States.
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6
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Leung GCH, Fung SSP, Dovey NRB, Raven EL, Hudson AJ. Precise determination of heme binding affinity in proteins. Anal Biochem 2019; 572:45-51. [PMID: 30807737 DOI: 10.1016/j.ab.2019.02.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 02/22/2019] [Accepted: 02/22/2019] [Indexed: 01/22/2023]
Abstract
Accumulating evidence suggests a new role for cellular heme as a signalling molecule, in which interactions with target proteins are more transient than found with traditionally-defined hemoproteins. To study this role, a precise method is needed for determining the heme-binding affinity (or dissociation constant, Kd). Estimates of Kd are commonly made following a spectrophotometric titration of an apo-protein with hemin. An impediment to precise determination is, however, the challenge in discriminating between the Soret absorbance for the product (holo-protein) and that for the titrant (hemin). An altogether different approach has been used in this paper to separate contributions made by these components to absorbance values. The pure component spectra and concentration profiles are estimated by a multivariate curve-resolution (MCR) algorithm. This approach has significant advantages over existing methods. First, a more precise determination of Kd can be made as concentration profiles for all three components (apo-protein/holo-protein/hemin) are determined and can be simultaneously fitted to a theoretical-binding model. Second, an absorption spectrum for the holo-protein is calculated. This is a unique advantage of MCR and attractive for investigating proteins in which the nature of heme binding has not, hitherto, been characterised because the holo-protein spectrum provides information on the interaction.
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Affiliation(s)
- Galvin C-H Leung
- Department of Chemistry and the Leicester Institute of Structural & Chemical Biology, University of Leicester, Leicester, LE1 7RH, United Kingdom
| | - Simon S-P Fung
- Department of Chemistry and the Leicester Institute of Structural & Chemical Biology, University of Leicester, Leicester, LE1 7RH, United Kingdom
| | - Nicholas R B Dovey
- Department of Chemistry and the Leicester Institute of Structural & Chemical Biology, University of Leicester, Leicester, LE1 7RH, United Kingdom
| | - Emma L Raven
- School of Chemistry, University of Bristol, Bristol, BS8 1TS, United Kingdom
| | - Andrew J Hudson
- Department of Chemistry and the Leicester Institute of Structural & Chemical Biology, University of Leicester, Leicester, LE1 7RH, United Kingdom.
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7
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Hanna DA, Hu R, Kim H, Martinez-Guzman O, Torres MP, Reddi AR. Heme bioavailability and signaling in response to stress in yeast cells. J Biol Chem 2018; 293:12378-12393. [PMID: 29921585 DOI: 10.1074/jbc.ra118.002125] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Revised: 06/15/2018] [Indexed: 12/28/2022] Open
Abstract
Protoheme (hereafter referred to as heme) is an essential cellular cofactor and signaling molecule that is also potentially cytotoxic. To mitigate heme toxicity, heme synthesis and degradation are tightly coupled to heme utilization in order to limit the intracellular concentration of "free" heme. Such a model, however, would suggest that a readily accessible steady-state, bioavailable labile heme (LH) pool is not required for supporting heme-dependent processes. Using the yeast Saccharomyces cerevisiae as a model and fluorescent heme sensors, site-specific heme chelators, and molecular genetic approaches, we found here that 1) yeast cells preferentially use LH in heme-depleted conditions; 2) sequestration of cytosolic LH suppresses heme signaling; and 3) lead (Pb2+) stress contributes to a decrease in total heme, but an increase in LH, which correlates with increased heme signaling. We also observed that the proteasome is involved in the regulation of the LH pool and that loss of proteasomal activity sensitizes cells to Pb2+ effects on heme homeostasis. Overall, these findings suggest an important role for LH in supporting heme-dependent functions in yeast physiology.
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Affiliation(s)
| | - Rebecca Hu
- From the School of Chemistry and Biochemistry
| | - Hyojung Kim
- From the School of Chemistry and Biochemistry.,School of Biological Sciences, and
| | | | - Matthew P Torres
- School of Biological Sciences, and.,Parker Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Amit R Reddi
- From the School of Chemistry and Biochemistry, .,Parker Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, Georgia 30332
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8
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Stott LA, Prosser KE, Berdichevsky EK, Walsby CJ, Warren JJ. Lowering water oxidation overpotentials using the ionisable imidazole of copper(2-(2'-pyridyl)imidazole). Chem Commun (Camb) 2017; 53:651-654. [PMID: 27990513 DOI: 10.1039/c6cc09208j] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Rapid and low overpotential oxidation of water to dioxygen remains a key hurdle for storage of solar energy. Here, we address this issue by demonstrating that deprotonation of 2-(2'-pyridyl)-imidazole (pimH)-ligated copper complexes promotes water oxidation at low overpotential and low catalyst loading. This improves upon other work on homogeneous copper-based water oxidation catalysts, which are highly active, but limited by high overpotentials. EPR and UV-vis spectroscopic evaluation of catalyst speciation shows that at pH ≥ 12 coordinated pimH is deprotonated and a bis(hydroxide) Cu2+ active catalyst forms. Rapid electrochemical water oxidation (35 s-1, 0.85 V onset potential) was observed with 150 μM catalyst. These results demonstrate that catalytic water oxidation potentials can be shifted by hundreds of mV in homogeneous metal catalysts bearing an ionisable imidazole ligand.
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Affiliation(s)
- Leea A Stott
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby BC V5A 1S6, Canada.
| | - Kathleen E Prosser
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby BC V5A 1S6, Canada.
| | - Ellan K Berdichevsky
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby BC V5A 1S6, Canada.
| | - Charles J Walsby
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby BC V5A 1S6, Canada.
| | - Jeffrey J Warren
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby BC V5A 1S6, Canada. and Canadian Institute for Applied Research, CIFAR Azrieli Global Scholar and Bio-Inspired Solar Energy Programs, Toronto, ON M5G 1Z8, Canada
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9
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Hanna DA, Martinez-Guzman O, Reddi AR. Heme Gazing: Illuminating Eukaryotic Heme Trafficking, Dynamics, and Signaling with Fluorescent Heme Sensors. Biochemistry 2017; 56:1815-1823. [PMID: 28316240 DOI: 10.1021/acs.biochem.7b00007] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Heme (iron protoporphyrin IX) is an essential protein prosthetic group and signaling molecule required for most life on Earth. All heme-dependent processes require the dynamic and rapid mobilization of heme from sites of synthesis or uptake to hemoproteins present in virtually every subcellular compartment. The cytotoxicity and hydrophobicity of heme necessitate that heme mobilization be carefully controlled to mitigate the deleterious effects of this essential toxin. Indeed, a number of disorders, including certain cancers, cardiovascular diseases, and aging and age-related neurodegenerative diseases, are tied to defects in heme homeostasis. However, the molecules and mechanisms that mediate heme transport and trafficking, and the dynamics of these processes, are poorly understood. This is in large part due to the lack of physical tools for probing cellular heme. Herein, we discuss the recent development of fluorescent probes that can monitor and image kinetically labile heme with respect to its mobilization and role in signaling. In particular, we will highlight how heme gazing with these tools can uncover new heme trafficking factors upon being integrated with genetic screens and illuminate the concentration, subcellular distribution, and dynamics of labile heme in various physiological contexts. Altogether, the monitoring of labile heme, along with recent biochemical and cell biological studies demonstrating the reversible regulation of certain cellular processes by heme, is challenging us to reconceptualize heme from being a static cofactor buried in protein active sites to a dynamic and mobile signaling molecule.
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Affiliation(s)
- David A Hanna
- School of Chemistry and Biochemistry and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - Osiris Martinez-Guzman
- School of Chemistry and Biochemistry and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - Amit R Reddi
- School of Chemistry and Biochemistry and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
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10
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Abstract
Complete thermodynamic descriptions of the interactions of cofactors with proteins via equilibrium studies are challenging, but are essential to the evaluation of designed metalloproteins. While decades of studies on protein-protein interaction thermodynamics provide a strong underpinning to the successful computational design of novel protein folds and de novo proteins with enzymatic activity, the corresponding paucity of data on metal-protein interaction thermodynamics limits the success of computational metalloprotein design efforts. By evaluating the thermodynamics of metal-protein interactions via equilibrium binding studies, protein unfolding free energy determinations, proton competition equilibria, and electrochemistry, a more robust basis for the computational design of metalloproteins may be provided. Our laboratory has shown that such studies provide detailed insight into the assembly and stability of designed metalloproteins, allow for parsing apart the free energy contributions of metal-ligand interactions from those of porphyrin-protein interactions in hemeproteins, and even reveal their mechanisms of proton-coupled electron transfer. Here, we highlight studies that reveal the complex interplay between the various equilibria that underlie metalloprotein assembly and stability and the utility of making these detailed measurements.
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Affiliation(s)
- B R Gibney
- Brooklyn College, Brooklyn, NY, United States; Ph.D. Programs in Chemistry and Biochemistry, The Graduate Center of the City University of New York, New York, NY, United States.
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11
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Heme dynamics and trafficking factors revealed by genetically encoded fluorescent heme sensors. Proc Natl Acad Sci U S A 2016; 113:7539-44. [PMID: 27247412 DOI: 10.1073/pnas.1523802113] [Citation(s) in RCA: 126] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Heme is an essential cofactor and signaling molecule. Heme acquisition by proteins and heme signaling are ultimately reliant on the ability to mobilize labile heme (LH). However, the properties of LH pools, including concentration, oxidation state, distribution, speciation, and dynamics, are poorly understood. Herein, we elucidate the nature and dynamics of LH using genetically encoded ratiometric fluorescent heme sensors in the unicellular eukaryote Saccharomyces cerevisiae We find that the subcellular distribution of LH is heterogeneous; the cytosol maintains LH at ∼20-40 nM, whereas the mitochondria and nucleus maintain it at concentrations below 2.5 nM. Further, we find that the signaling molecule nitric oxide can initiate the rapid mobilization of heme in the cytosol and nucleus from certain thiol-containing factors. We also find that the glycolytic enzyme glyceraldehyde phosphate dehydrogenase constitutes a major cellular heme buffer, and is responsible for maintaining the activity of the heme-dependent nuclear transcription factor heme activator protein (Hap1p). Altogether, we demonstrate that the heme sensors can be used to reveal fundamental aspects of heme trafficking and dynamics and can be used across multiple organisms, including Escherichia coli, yeast, and human cell lines.
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12
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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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13
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Brisendine JM, Koder RL. Fast, cheap and out of control--Insights into thermodynamic and informatic constraints on natural protein sequences from de novo protein design. BIOCHIMICA ET BIOPHYSICA ACTA 2016; 1857:485-492. [PMID: 26498191 PMCID: PMC4856154 DOI: 10.1016/j.bbabio.2015.10.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Accepted: 10/06/2015] [Indexed: 12/15/2022]
Abstract
The accumulated results of thirty years of rational and computational de novo protein design have taught us important lessons about the stability, information content, and evolution of natural proteins. First, de novo protein design has complicated the assertion that biological function is equivalent to biological structure - demonstrating the capacity to abstract active sites from natural contexts and paste them into non-native topologies without loss of function. The structure-function relationship has thus been revealed to be either a generality or strictly true only in a local sense. Second, the simplification to "maquette" topologies carried out by rational protein design also has demonstrated that even sophisticated functions such as conformational switching, cooperative ligand binding, and light-activated electron transfer can be achieved with low-information design approaches. This is because for simple topologies the functional footprint in sequence space is enormous and easily exceeds the number of structures which could have possibly existed in the history of life on Earth. Finally, the pervasiveness of extraordinary stability in designed proteins challenges accepted models for the "marginal stability" of natural proteins, suggesting that there must be a selection pressure against highly stable proteins. This can be explained using recent theories which relate non-equilibrium thermodynamics and self-replication. This article is part of a Special Issue entitled Biodesign for Bioenergetics--The design and engineering of electronc transfer cofactors, proteins and protein networks, edited by Ronald L. Koder and J.L. Ross Anderson.
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Affiliation(s)
- Joseph M Brisendine
- Department of Physics, The City College of New York, New York, NY 10031, United States; The Graduate Program in Biochemistry, The Graduate Center of CUNY, New York, NY 10016, United States
| | - Ronald L Koder
- Department of Physics, The City College of New York, New York, NY 10031, United States; Graduate Programs of Physics, Chemistry and Biochemistry, The Graduate Center of CUNY, New York, NY 10016, United States.
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14
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Hosseinzadeh P, Mirts EN, Pfister TD, Gao YG, Mayne C, Robinson H, Tajkhorshid E, Lu Y. Enhancing Mn(II)-Binding and Manganese Peroxidase Activity in a Designed Cytochrome c Peroxidase through Fine-Tuning Secondary-Sphere Interactions. Biochemistry 2016; 55:1494-502. [PMID: 26885726 DOI: 10.1021/acs.biochem.5b01299] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Noncovalent second-shell interactions are important in controlling metal-binding affinity and activity in metalloenzymes, but fine-tuning these interactions in designed metalloenzymes has not been fully explored. As a result, most designed metalloenzymes have low metal-binding affinity and activity. Here we identified three mutations in the second coordination shell of an engineered Mn(II)-binding site in cytochrome c peroxidase (called MnCcP.1, containing Glu45, Glu37, and Glu181 ligands) that mimics the native manganese peroxidase (MnP), and explored their effects on both Mn(II)-binding affinity and MnP activity. First, removing a hydrogen bond to Glu45 through Tyr36Phe mutation enhanced Mn(II)-binding affinity, as evidenced by a 2.8-fold decrease in the KM of Mn(II) oxidation. Second, introducing a salt bridge through Lys179Arg mutation improved Glu35 and Glu181 coordination to Mn(II), decreasing KM 2.6-fold. Third, eliminating a steric clash that prevented Glu37 from orienting toward Mn(II) resulted in an 8.6-fold increase in kcat/KM, arising primarily from a 3.6-fold decrease in KM, with a KM value comparable to that of the native enzyme (0.28 mM vs 0.19 mM for Pleurotus eryngii MnP PS3). We further demonstrated that while the effects of Tyr36Phe and Lys179Arg mutations are additive, because involved in secondary-shell interactions to different ligands, other combinations of mutations were antagonistic because they act on different aspects of the Mn(II) coordination at the same residues. Finally, we showed that these MnCcP variants are functional models of MnP that mimic its activity in both Mn(II) oxidation and degradation of a phenolic lignin model compound and kraft lignin. In addition to achieving KM in a designed protein that is similar to the that of native enzyme, our results offer molecular insight into the role of noncovalent interactions around metal-binding sites for improving metal binding and overall activity; such insight can be applied to rationally enhance these properties in other metalloenzymes and their models.
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Affiliation(s)
| | | | | | | | | | - Howard Robinson
- Department of Biology, Brookhaven National Laboratory , Upton, New York 11973, United States
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15
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Liu J, Chakraborty S, Hosseinzadeh P, Yu Y, Tian S, Petrik I, Bhagi A, Lu Y. Metalloproteins containing cytochrome, iron-sulfur, or copper redox centers. Chem Rev 2014; 114:4366-469. [PMID: 24758379 PMCID: PMC4002152 DOI: 10.1021/cr400479b] [Citation(s) in RCA: 559] [Impact Index Per Article: 55.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Indexed: 02/07/2023]
Affiliation(s)
- Jing Liu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Saumen Chakraborty
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Parisa Hosseinzadeh
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yang Yu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Shiliang Tian
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Igor Petrik
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Ambika Bhagi
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yi Lu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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16
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Weinberg DR, Gagliardi CJ, Hull JF, Murphy CF, Kent CA, Westlake BC, Paul A, Ess DH, McCafferty DG, Meyer TJ. Proton-Coupled Electron Transfer. Chem Rev 2012; 112:4016-93. [DOI: 10.1021/cr200177j] [Citation(s) in RCA: 1125] [Impact Index Per Article: 93.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- David R. Weinberg
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
- Department of Physical and Environmental
Sciences, Colorado Mesa University, 1100 North Avenue, Grand Junction,
Colorado 81501-3122, United States
| | - Christopher J. Gagliardi
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
| | - Jonathan F. Hull
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
| | - Christine Fecenko Murphy
- Department
of Chemistry, B219
Levine Science Research Center, Box 90354, Duke University, Durham,
North Carolina 27708-0354, United States
| | - Caleb A. Kent
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
| | - Brittany C. Westlake
- The American Chemical Society,
1155 Sixteenth Street NW, Washington, District of Columbia 20036,
United States
| | - Amit Paul
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
| | - Daniel H. Ess
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
| | - Dewey Granville McCafferty
- Department
of Chemistry, B219
Levine Science Research Center, Box 90354, Duke University, Durham,
North Carolina 27708-0354, United States
| | - Thomas J. Meyer
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
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17
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Shinde S, Cordova JM, Woodrum BW, Ghirlanda G. Modulation of function in a minimalist heme-binding membrane protein. J Biol Inorg Chem 2012; 17:557-64. [PMID: 22307279 DOI: 10.1007/s00775-012-0876-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Accepted: 01/14/2012] [Indexed: 12/21/2022]
Abstract
De novo designed heme-binding proteins have been used successfully to recapitulate features of natural hemoproteins. This approach has now been extended to membrane-soluble model proteins. Our group designed a functional hemoprotein, ME1, by engineering a bishistidine binding site into a natural membrane protein, glycophorin A (Cordova et al. in J Am Chem Soc 129:512-518, 2007). ME1 binds iron(III) protoporphyrin IX with submicromolar affinity, has a redox potential of -128 mV, and displays peroxidase activity. Here, we show the effect of aromatic residues in modulating the redox potential in the context of a membrane-soluble model system. We designed aromatic interactions with the heme through a single-point mutant, G25F, in which a phenylalanine is designed to dock against the porphyrin ring. This mutation results in roughly tenfold tighter binding to iron(III) protoporphyrin IX (K(d,app) = 6.5 × 10(-8) M), and lowers the redox potential of the cofactor to -172 mV. This work demonstrates that specific design features aimed at controlling the properties of bound cofactors can be introduced in a minimalist membrane hemoprotein model. The ability to modulate the redox potential of cofactors embedded in artificial membrane proteins is crucial for the design of electron transfer chains across membranes in functional photosynthetic devices.
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Affiliation(s)
- Sandip Shinde
- Department of Chemistry and Biochemistry, ASU, Tempe, AZ 85287, USA
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18
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Zhang L, Anderson JLR, Ahmed I, Norman JA, Negron C, Mutter AC, Dutton PL, Koder RL. Manipulating cofactor binding thermodynamics in an artificial oxygen transport protein. Biochemistry 2011; 50:10254-61. [PMID: 22004125 DOI: 10.1021/bi201242a] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report the mutational analysis of an artificial oxygen transport protein, HP7, which operates via a mechanism akin to that of human neuroglobin and cytoglobin. This protein destabilizes one of two heme-ligating histidine residues by coupling histidine side chain ligation with the burial of three charged glutamate residues on the same helix. Replacement of these glutamate residues with alanine, which is uncharged, increases the affinity of the distal histidine ligand by a factor of 13. Paradoxically, it also decreases heme binding affinity by a factor of 5 in the reduced state and 60 in the oxidized state. Application of a three-state binding model, in which an initial pentacoordinate binding event is followed by a protein conformational change to hexacoordinate, provides insight into the mechanism of this seemingly counterintuitive result: the initial pentacoordinate encounter complex is significantly destabilized by the loss of the glutamate side chains, and the increased affinity for the distal histidine only partially compensates for that. These results point to the importance of considering each oxidation and conformational state in the design of functional artificial proteins.
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Affiliation(s)
- Lei Zhang
- Department of Physics, The City College of New York, New York, New York 10031, United States
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19
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Costentin C, Robert M, Savéant JM. Update 1 of: Electrochemical Approach to the Mechanistic Study of Proton-Coupled Electron Transfer. Chem Rev 2010; 110:PR1-40. [DOI: 10.1021/cr100038y] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Cyrille Costentin
- Laboratoire d’Electrochimie Moléculaire, Unité Mixte de Recherche Université, CNRS No. 7591, Université Paris Diderot, 15 rue Jean de Baïf, 75013 Paris, France
- This is a Chemical Reviews Perennial Review. The root paper of this title was published in Chem. Rev. 2008, 108 (7), 2145−2179, DOI: 10.1021/cr068065t; Published (Web) July 11, 2008. Updates to the text appear in red type
| | - Marc Robert
- Laboratoire d’Electrochimie Moléculaire, Unité Mixte de Recherche Université, CNRS No. 7591, Université Paris Diderot, 15 rue Jean de Baïf, 75013 Paris, France
- This is a Chemical Reviews Perennial Review. The root paper of this title was published in Chem. Rev. 2008, 108 (7), 2145−2179, DOI: 10.1021/cr068065t; Published (Web) July 11, 2008. Updates to the text appear in red type
| | - Jean-Michel Savéant
- Laboratoire d’Electrochimie Moléculaire, Unité Mixte de Recherche Université, CNRS No. 7591, Université Paris Diderot, 15 rue Jean de Baïf, 75013 Paris, France
- This is a Chemical Reviews Perennial Review. The root paper of this title was published in Chem. Rev. 2008, 108 (7), 2145−2179, DOI: 10.1021/cr068065t; Published (Web) July 11, 2008. Updates to the text appear in red type
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20
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Smith LJ, Kahraman A, Thornton JM. Heme proteins--diversity in structural characteristics, function, and folding. Proteins 2010; 78:2349-68. [PMID: 20544970 DOI: 10.1002/prot.22747] [Citation(s) in RCA: 117] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The characteristics of heme prosthetic groups and their binding sites have been analyzed in detail in a data set of nonhomologous heme proteins. Variations in the shape, volume, and chemical composition of the binding site, in the mode of heme binding and in the number and nature of heme-protein interactions are found to result in significantly different heme environments in proteins with different functions in biology. Differences are also seen in the properties of the apo states of the proteins. The apo states of proteins that bind heme permanently in their functional form show some disorder, ranging from local unfolding in the heme binding pocket to complete unfolding to give a random coil. In contrast, proteins that bind heme transiently are fully folded in their apo and holo states, presumably allowing both apo and holo forms to remain biologically active resisting aggregation or proteolysis. The principles identified here provide a framework for the design of de novo proteins that will exhibit tight heme ligand binding and for the identification of the function of structural genomic target proteins with heme ligands.
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Affiliation(s)
- Lorna J Smith
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, Oxford OX1 3QR, United Kingdom.
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21
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Gámiz-Hernández AP, Kieseritzky G, Galstyan AS, Demir-Kavuk O, Knapp EW. Understanding properties of cofactors in proteins: redox potentials of synthetic cytochromes b. Chemphyschem 2010; 11:1196-206. [PMID: 20411561 DOI: 10.1002/cphc.200900889] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Haehnel et al. synthesized 399 different artificial cytochrome b (aCb) models. They consist of a template-assisted four-helix bundle with one embedded heme group. Their redox potentials were measured and cover the range from -148 to -89 mV. No crystal structures of these aCb are available. Therefore, we use the chemical composition and general structural principles to generate atomic coordinates of 31 of these aCb mutants, which are chosen to cover the whole interval of redox potentials. We start by modeling the coordinates of one aCb from scratch. Its structure remains stable after energy minimization and during molecular dynamics simulation over 2 ns. Based on this structure, coordinates of the other 30 aCb mutants are modeled. The calculated redox potentials for these 31 aCb agree within 10 mV with the experimental values in terms of root mean square deviation. Analysis of the dependence of heme redox potential on protein environment shows that the shifts in redox potentials relative to the model systems in water are due to the low-dielectric medium of the protein and the protonation states of the heme propionic acid groups, which are influenced by the surrounding amino acids. Alternatively, we perform a blind prediction of the same redox potentials using an empirical approach based on a linear scoring function and reach a similar accuracy. Both methods are useful to understand and predict heme redox potentials. Based on the modeled structure we can understand the detailed structural differences between aCb mutants that give rise to shifts in heme redox potential. On the other hand, one can explore the correlation between sequence variations and aCb redox potentials more directly and on much larger scale using the empirical prediction scheme, which--thanks to its simplicity--is much faster.
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Affiliation(s)
- Ana P Gámiz-Hernández
- Freie Universität Berlin, FB Biology, Chemistry, Pharmacy, Institute of Chemistry & Biochemistry, Fabeckstr. 36a, 14195 Berlin, Germany
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22
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Abstract
Proteins are nature's premier building blocks for constructing sophisticated nanoscale architectures that carry out complex tasks and chemical transformations. Some 70%-80% of all proteins are thought to be permanently oligomeric; that is, they are composed of multiple proteins that are held together in precise spatial organization through noncovalent interactions. Although it is of great fundamental interest to understand the physicochemical basis of protein self-assembly, the mastery of protein-protein interactions (PPIs) would also allow access to novel biomaterials with nature's favorite and most versatile building block. In this Account, we describe a new approach we have developed with this possibility in mind, metal-directed protein self-assembly (MDPSA), which utilizes the strength, directionality, and selectivity of metal-ligand interactions to control PPIs. At its core, MDPSA is inspired by supramolecular coordination chemistry, which exploits metal coordination for the self-assembly of small molecules into discrete, more-or-less predictable higher order structures. Proteins, however, are not exactly small molecules or simple metal ligands: they feature extensive, heterogeneous surfaces that can interact with each other and with metal ions in unpredictable ways. We begin by first describing the challenges of using entire proteins as molecular building blocks. We follow with an examination of our work on a model protein (cytochrome cb(562)), highlighting challenges toward establishing ground rules for MDPSA as well as progress in overcoming these challenges. Proteins are also nature's metal ligands of choice. In MDPSA, once metal ions guide proteins into forming large assemblies, they are by definition embedded within extensive interfaces formed between protein surfaces. These complex surfaces make an inorganic chemist's life somewhat difficult, yet they also provide a wide platform to modulate the metal coordination environment through distant, noncovalent interactions, exactly as natural metalloproteins and enzymes do. We describe our computational and experimental efforts toward restructuring the noncovalent interaction network formed between proteins surrounding the interfacial metal centers. This approach, of metal templating followed by the redesign of protein interfaces (metal-templated interface redesign, MeTIR), not only provides a route to engineer de novo PPIs and novel metal coordination environments but also suggests possible parallels with the evolution of metalloproteins.
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Affiliation(s)
- Eric N. Salgado
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093
| | - Robert J. Radford
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093
| | - F. Akif Tezcan
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093
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23
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Abstract
Metal coordination is a key structural and functional component of a large fraction of proteins. Given this dual role we considered the possibility that metal coordination may have played a templating role in the early evolution of protein folds and complexes. We describe here a rational design approach, Metal Templated Interface Redesign (MeTIR), that mimics the time course of a hypothetical evolutionary pathway for the formation of stable protein assemblies through an initial metal coordination event. Using a folded monomeric protein, cytochrome cb(562), as a building block we show that its non-self-associating surface can be made self-associating through a minimal number of mutations that enable Zn coordination. The protein interfaces in the resulting Zn-directed, D(2)-symmetrical tetramer are subsequently redesigned, yielding unique protein architectures that self-assemble in the presence or absence of metals. Aside from its evolutionary implications, MeTIR provides a route to engineer de novo protein interfaces and metal coordination environments that can be tuned through the extensive noncovalent bonding interactions in these interfaces.
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24
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Negron C, Fufezan C, Koder RL. Geometric constraints for porphyrin binding in helical protein binding sites. Proteins 2009; 74:400-16. [PMID: 18636480 DOI: 10.1002/prot.22143] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Helical bundles which bind heme and porphyrin cofactors have been popular targets for cofactor-containing de novo protein design. By analyzing a highly nonredundant subset of the protein databank we have determined a rotamer distribution for helical histidines bound to heme cofactors. Analysis of the entire nonredundant database for helical sequence preferences near the ligand histidine demonstrated little preference for amino acid side chain identity, size, or charge. Analysis of the database subdivided by ligand histidine rotamer, however, reveals strong preferences in each case, and computational modeling illuminates the structural basis for some of these findings. The majority of the rotamer distribution matches that predicted by molecular simulation of a single porphyrin-bound histidine residue placed in the center of an all-alanine helix, and the deviations explain two prominent features of natural heme protein binding sites: heme distortion in the case of the cytochromes C in the m166 histidine rotamer, and a highly prevalent glycine residue in the t73 histidine rotamer. These preferences permit derivation of helical consensus sequence templates which predict optimal side chain-cofactor packing interactions for each rotamer. These findings thus promise to guide future design endeavors not only in the creation of higher affinity heme and porphyrin binding sites, but also in the direction of bound cofactor geometry.
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Affiliation(s)
- Christopher Negron
- Department of Physics, the City College of New York, New York, New York 10031, USA
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25
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Costentin C. Electrochemical Approach to the Mechanistic Study of Proton-Coupled Electron Transfer. Chem Rev 2008; 108:2145-79. [DOI: 10.1021/cr068065t] [Citation(s) in RCA: 328] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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26
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Thompson AM, Reddi AR, Shi X, Goldbeck RA, Moënne-Loccoz P, Gibney BR, Holman TR. Measurement of the heme affinity for yeast dap1p, and its importance in cellular function. Biochemistry 2007; 46:14629-37. [PMID: 18031064 DOI: 10.1021/bi7013739] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Current studies on the Saccharomyces cerevisiae protein Dap1p have demonstrated a heme-related function within the ergosterol biosynthetic pathway. Here we present data to further the understanding of the role of heme in the proper biological functioning of Dap1p in cellular processes. First, we examined the role of Dap1p in stabilizing the P450 enzyme, Erg11p, a key regulatory protein in ergosterol biosynthesis. Our data indicate that the absence of Dap1p does not affect Erg11p mRNA, protein expression levels, or the protein degradation rates in S. Cerevisaie. Second, in order to probe the role of heme in the biological functioning of Dap1p, we measured ferric and ferrous heme binding affinities for Dap1p and the mutant Dap1pY138F, as well as equilibrium midpoint reduction potentials of the Fe(III)/Fe(II) couples. Our results show that both wild-type and mutant proteins bind heme in a 1:1 fashion, possessing tight ferric heme affinities, KD values of 400 pM and 200 nM, respectively, but exhibiting weak ferrous affinities, 2 and 10 microM, respectively. Additionally, the measured reduction potential of Dap1p, which was found to be -307 mV, is similar to that of other monotyrosinate hemoproteins. Although previous reports show the weaker affinity of Dap1pY138F for ferric heme lowers the production of ergosterol with respect to wild-type Dap1p in S. pombe, we find that Dap1pY138F expression is still sufficient to rescue the growth sensitivity of dap1Delta to fluconazole and methyl methanesulfonate in S. cerevisiae. Various interpretations of these results are discussed with respect to Dap1p function in the cell.
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Affiliation(s)
- Alisha M Thompson
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, USA
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27
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Affiliation(s)
- My Hang V Huynh
- DE-1: High Explosive Science and Technology Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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28
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Reedy CJ, Elvekrog MM, Gibney BR. Development of a heme protein structure-electrochemical function database. Nucleic Acids Res 2007; 36:D307-13. [PMID: 17933771 PMCID: PMC2238922 DOI: 10.1093/nar/gkm814] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Proteins containing heme, iron(protoporphyrin IX) and its variants, continue to be one of the most-studied classes of biomolecules due to their diverse range of biological functions. The literature is abundant with reports of structural and functional characterization of individual heme proteins which demonstrate that heme protein reduction potential values, Em, span the range from –550 mV to +450 mV versus SHE. In order to unite these data for the purposes of global analysis, a new web-based resource of heme protein structure–function relationships is presented: the Heme Protein Database (HPD). This database is the first of its kind to combine heme protein structural classifications including protein fold, heme type and heme axial ligands, with heme protein reduction potential values in a web-searchable format. The HPD is located at http://heme.chem.columbia.edu/heme.php. The data illustrate that heme protein Em values are modulated over a 300 mV range by the type of global protein fold, a 600 mV range by the type of porphyrin and an 800 mV range by the axial ligands. Thus, the 1 V range observed in heme protein reduction potential values in biological systems arises from subtle combinations of these various factors.
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Affiliation(s)
- Charles J Reedy
- Department of Chemistry, Columbia University, 3000 Broadway, MC 3121, New York, NY 10027, USA
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