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Pinter TBJ, Koebke KJ, Pecoraro VL. Katalyse und Elektronentransfer in helikalen De‐novo‐Gerüststrukturen. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201907502] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Tolbert AE, Ervin CS, Ruckthong L, Paul TJ, Jayasinghe-Arachchige VM, Neupane KP, Stuckey JA, Prabhakar R, Pecoraro VL. Heteromeric three-stranded coiled coils designed using a Pb(II)(Cys) 3 template mediated strategy. Nat Chem 2020; 12:405-411. [PMID: 32123337 DOI: 10.1038/s41557-020-0423-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 01/19/2020] [Indexed: 11/09/2022]
Abstract
Three-stranded coiled coils are peptide structures constructed from amphipathic heptad repeats. Here we show that it is possible to form pure heterotrimeric three-stranded coiled coils by combining three distinct characteristics: (1) a cysteine sulfur layer for metal coordination, (2) a thiophilic, trigonal pyramidal metalloid (Pb(II)) that binds to these sulfurs and (3) an adjacent layer of reduced steric bulk generating a cavity where water can hydrogen bond to the cysteine sulfur atoms. Cysteine substitution in an a site yields Pb(II)A2B heterotrimers, while d sites provide pure Pb(II)C2D or Pb(II)CD2 scaffolds. Altering the metal from Pb(II) to Hg(II) or shifting the relative position of the sterically less demanding layer removes heterotrimer specificity. Because only two of the eight or ten hydrophobic layers are perturbed, catalytic sites can be introduced at other regions of the scaffold. A Zn(II)(histidine)3(H2O) centre can be incorporated at a remote location without perturbing the heterotrimer selectivity, suggesting a unique strategy to prepare dissymmetric catalytic sites within self-assembling de novo-designed proteins.
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Lutter JC, Eliseeva SV, Collet G, Martinić I, Kampf JW, Schneider BL, Carichner A, Sobilo J, Lerondel S, Petoud S, Pecoraro VL. Iodinated Metallacrowns: Toward Combined Bimodal Near‐Infrared and X‐Ray Contrast Imaging Agents. Chemistry 2020; 26:1274-1277. [DOI: 10.1002/chem.201905241] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Indexed: 12/21/2022]
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Nguyen TN, Eliseeva SV, Chow CY, Kampf JW, Petoud S, Pecoraro VL. Peculiarities of crystal structures and photophysical properties of GaIII/LnIII metallacrowns with a non-planar [12-MC-4] core. Inorg Chem Front 2020. [DOI: 10.1039/c9qi01647c] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The direct synthetic approach can be used to create a series of visible and near-infrared emitting GaIII/LnIII metallacrowns with a non-planar [12-MC-4] core.
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Ostrowska M, Toporivska Y, Golenya IA, Shova S, Fritsky IO, Pecoraro VL, Gumienna-Kontecka E. Explaining How α-Hydroxamate Ligands Control the Formation of Cu(II)-, Ni(II)-, and Zn(II)-Containing Metallacrowns. Inorg Chem 2019; 58:16642-16659. [DOI: 10.1021/acs.inorgchem.9b02724] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Jung J, Islam MA, Pecoraro VL, Mallah T, Berthon C, Bolvin H. Derivation of Lanthanide Series Crystal Field Parameters From First Principles. Chemistry 2019; 25:15112-15122. [PMID: 31496013 DOI: 10.1002/chem.201903141] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 08/28/2019] [Indexed: 11/08/2022]
Abstract
Two series of lanthanide complexes have been chosen to analyze trends in the magnetic properties and crystal field parameters (CFPs) along the two series: The highly symmetric LnZn16 (picHA)16 series (Ln=Tb, Dy, Ho, Er, Yb; picHA=picolinohydroxamic acid) and the [Ln(dpa)3 ](C3 H5 N2 )3 ⋅3H2 O series (Ln=Ce-Yb; dpa=2,6-dipicolinic acid) with approximate three-fold symmetry. The first series presents a compressed coordination sphere of eight oxygen atoms whereas in the second series, the coordination sphere consists of an elongated coordination sphere formed of six oxygen atoms. The CFPs have been deduced from ab initio calculations using two methods: The AILFT (ab initio ligand field theory) method, in which the parameters are determined at the orbital level, and the ITO (irreducible tensor operator) decomposition, in which the problems are treated at the many-electron level. It has been found that the CFPs are transferable from one derivative to another, within a given series, as a first approximation. The sign of the second-order parameter B 0 2 differs in the two series, reflecting the different environments. It has been found that the use of the strength parameter S allows for an easy comparison between complexes. Furthermore, in both series, the parameters have been found to decrease in magnitude along the series, and this decrease is attributed to covalent effects.
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Koebke KJ, Pecoraro VL. Noncoded Amino Acids in de Novo Metalloprotein Design: Controlling Coordination Number and Catalysis. Acc Chem Res 2019; 52:1160-1167. [PMID: 30933479 DOI: 10.1021/acs.accounts.9b00032] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The relationship between structure and function has long been one of the major points of investigation in Biophysics. Understanding how much, or how little, of a protein's often complicated structure is necessary for its function can lead to directed therapeutic strategies and would allow one to design proteins for specific desired functions. Studying protein function by de novo design builds the functionality from the ground up in a completely unrelated and noncoded protein scaffold. Our lab has used this strategy to study heavy and transition metal binding within the TRI family of three stranded coiled coil (3SCC) constructs to understand coordination geometry and metalloenzyme catalytic control within a protein environment. These peptides contain hydrophobic layers within the interior of the 3SCC, which one can mutate to metal binding residues to create a minimal metal binding site, while solid phase synthesis allows our lab to easily incorporate a number of noncoded amino acids including d enantiomers of binding or secondary coordination sphere amino acids, penicillamine, or methylated versions of histidine. Our studies of Cd(II) binding to Cys3 environments have determined, largely through the use of 113Cd NMR and 111mCd PAC, that the coordination environment around a heavy metal can be controlled by incorporating noncoded amino acids in either the primary or secondary coordination spheres. We found mutating the metal binding amino acids to l-Pen can enforce trigonal Cd(II)S3 geometry exclusively compared to the mixed coordination determined for l-Cys coordination. The same result can be achieved with secondary sphere mutations as well by incorporating d-Leu above a Cys3. We hypothesize this latter effect is due to the increased steric packing above the metal binding site that occurs when the l-Leu oriented toward the N-terminus of the scaffold is mutated to d-Leu and oriented toward the C-terminus. Mutating the layer below Cys3 to d-Leu instead formed a mixed 4- and 5-coordinate Cd(II)S3(H2O) and Cd(II)S3(H2O)2 construct as steric bulk was decreased below the metal binding site. We have also applied noncoded amino acids to metalloenzyme systems by incorporating His residues that are methylated at the δ- or ε-nitrogen to enforce Cu(I) ligation to the opposite open nitrogen of His and found a 2 orders of magnitude increased catalytic efficiency for nitrite reductase activity with ε-nitrogen coordination compared to δ-nitrogen. These results exemplify the ability to tune coordination environment and catalytic efficiency within a de novo scaffold as well as the utility of noncoded amino acids to increase the chemist's toolbox. By furthering our understanding of metalloprotein design one could envision, through our use of amino acids not normally available to nature, that protein design laboratories will soon be capable of outperforming the native systems previously used as their benchmark of successful design. The ability to design proteins at this level would have far reaching and exciting benefits within various fields including medical and industrial applications.
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Koebke KJ, Yu F, Van Stappen C, Pinter TBJ, Deb A, Penner-Hahn JE, Pecoraro VL. Methylated Histidines Alter Tautomeric Preferences that Influence the Rates of Cu Nitrite Reductase Catalysis in Designed Peptides. J Am Chem Soc 2019; 141:7765-7775. [PMID: 30983335 PMCID: PMC6824201 DOI: 10.1021/jacs.9b00196] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Copper proteins have the capacity to serve as both redox active catalysts and purely electron transfer centers. A longstanding question in this field is how the function of histidine ligated Cu centers are modulated by δ vs ε-nitrogen ligation of the imidazole. Evaluating the impact of these coordination modes on structure and function by comparative analysis of deposited crystal structures is confounded by factors such as differing protein folds and disparate secondary coordination spheres that make direct comparison of these isomers difficult. Here, we present a series of de novo designed proteins using the noncanonical amino acids 1-methyl-histidine and 3-methyl-histidine to create Cu nitrite reductases where δ- or ε-nitrogen ligation is enforced by the opposite nitrogen's methylation as a means of directly comparing these two ligation states in the same protein fold. We find that ε-nitrogen ligation allows for a better nitrite reduction catalyst, displaying 2 orders of magnitude higher activity than the δ-nitrogen ligated construct. Methylation of the δ nitrogen, combined with a secondary sphere mutation we have previously published, has produced a new record for efficiency within a homogeneous aqueous system, improving by 1 order of magnitude the previously published most efficient construct. Furthermore, we have measured Michaelis-Menten kinetics on these highly active constructs, revealing that the remaining barriers to matching the catalytic efficiency ( kcat/ KM) of native Cu nitrite reductase involve both substrate binding ( KM) and catalysis ( kcat).
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Ruckthong L, Stuckey JA, Pecoraro VL. How Outer Coordination Sphere Modifications Can Impact Metal Structures in Proteins: A Crystallographic Evaluation. Chemistry 2019; 25:6773-6787. [PMID: 30861211 PMCID: PMC6510599 DOI: 10.1002/chem.201806040] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Indexed: 11/06/2022]
Abstract
A challenging objective of de novo metalloprotein design is to control of the outer coordination spheres of an active site to fine tune metal properties. The well-defined three stranded coiled coils, TRI and CoilSer peptides, are used to address this question. Substitution of Cys for Leu yields a thiophilic site within the core. Metals such as HgII , PbII , and AsIII result in trigonal planar or trigonal pyramidal geometries; however, spectroscopic studies have shown that CdII forms three-, four- or five-coordinate CdII S3 (OH2 )x (in which x=0-2) when the outer coordination spheres are perturbed. Unfortunately, there has been little crystallographic examination of these proteins to explain the observations. Here, the high-resolution X-ray structures of apo- and mercurated proteins are compared to explain the modifications that lead to metal coordination number and geometry variation. It reveals that Ala substitution for Leu opens a cavity above the Cys site allowing for water excess, facilitating CdII S3 (OH2 ). Replacement of Cys by Pen restricts thiol rotation, causing a shift in the metal-binding plane, which displaces water, forming CdII S3 . Residue d-Leu, above the Cys site, reorients the side chain towards the Cys layer, diminishing the space for water accommodation yielding CdII S3 , whereas d-Leu below opens more space, allowing for equal CdII S3 (OH2 ) and CdII S3 (OH2 )2 . These studies provide insights into how to control desired metal geometries in metalloproteins by using coded and non-coded amino acids.
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Lutter JC, Lopez Bermudez BA, Nguyen TN, Kampf JW, Pecoraro VL. Functionalization of luminescent lanthanide-gallium metallacrowns using copper-catalyzed alkyne-azide cycloaddition and thiol-maleimide Michael addition. J Inorg Biochem 2019; 192:119-125. [DOI: 10.1016/j.jinorgbio.2018.12.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 12/21/2018] [Indexed: 10/27/2022]
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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 DOI: 10.1021/acs.inorgchem.8b01989] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [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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Koebke KJ, Pecoraro VL. Development of de Novo Copper Nitrite Reductases: Where We Are and Where We Need To Go. ACS Catal 2018; 8:8046-8057. [PMID: 30294504 DOI: 10.1021/acscatal.8b02153] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The development of redox-active metalloprotein catalysts is a challenging objective of de novo protein design. Within this Perspective we detail our efforts to create a redox-active Cu nitrite reductase (NiR) by incorporating Cu into the hydrophobic interior of well-defined three-stranded coiled coils (3SCCs). The scaffold contains three histidine residues that provide a layer of three nitrogen donors that mimic the type 2 catalytic site of NiR. We have found that this strategy successfully produces an active and stable CuNiR model that functions for over 1000 turnovers. Spectroscopic evidence indicates that the Cu(I) site has a lower coordination number in comparison to the enzyme, whereas the Cu(II) geometry may more faithfully reproduce the NiR type 2 center. Mutations at the helical interface successfully produce a hydrogen bond between an interfacial Glu residue and the Culigating His residue, which allows for the tuning of the redox potential over a 100 mV range. We successfully created constructs with as much as a 120-fold improvement from the original design by modifying the steric bulk above or below the Cu binding site. These systems are now the most active water-soluble and stable artificial NiR catalysts yet produced. Several avenues for improving the catalytic efficiency of later designs are detailed within this Perspective, including adjustment of their resting oxidation state, the use of asymmetric scaffolds to allow for single amino acid mutation within the second coordination sphere, and the design of hydrogen-bonding networks to tune residue orientation and electronics. Through these studies the TRI-H system has given insight into the difficulties that arise in creating a de novo redox active enzyme. Work to improve upon this model will provide strategies by which redox-active de novo enzymes may be tuned and detail how native enzymes accomplish catalytic efficiencies through proton gated redox catalysis.
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Marzaroli V, Marchió L, Spigolon G, Licini G, Pecoraro VL, Tegoni M. Engeneering novel porous 3D metallacrown frameworks, through the ligand periphery design. Acta Crystallogr A Found Adv 2018. [DOI: 10.1107/s2053273318089635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Lutter JC, Eliseeva SV, Kampf JW, Petoud S, Pecoraro VL. A Unique Ln
III
{[3.3.1]Ga
III
Metallacryptate} Series That Possesses Properties of Slow Magnetic Relaxation and Visible/Near‐Infrared Luminescence. Chemistry 2018; 24:10773-10783. [DOI: 10.1002/chem.201801355] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Indexed: 11/06/2022]
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Tebo AG, Pinter TBJ, García-Serres R, Speelman AL, Tard C, Sénéque O, Blondin G, Latour JM, Penner-Hahn J, Lehnert N, Pecoraro VL. Development of a Rubredoxin-Type Center Embedded in a de Dovo-Designed Three-Helix Bundle. Biochemistry 2018; 57:2308-2316. [PMID: 29561598 DOI: 10.1021/acs.biochem.8b00091] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Protein design is a powerful tool for interrogating the basic requirements for the function of a metal site in a way that allows for the selective incorporation of elements that are important for function. Rubredoxins are small electron transfer proteins with a reduction potential centered near 0 mV (vs normal hydrogen electrode). All previous attempts to design a rubredoxin site have focused on incorporating the canonical CXXC motifs in addition to reproducing the peptide fold or using flexible loop regions to define the morphology of the site. We have produced a rubredoxin site in an utterly different fold, a three-helix bundle. The spectra of this construct mimic the ultraviolet-visible, Mössbauer, electron paramagnetic resonance, and magnetic circular dichroism spectra of native rubredoxin. Furthermore, the measured reduction potential suggests that this rubredoxin analogue could function similarly. Thus, we have shown that an α-helical scaffold sustains a rubredoxin site that can cycle with the desired potential between the Fe(II) and Fe(III) states and reproduces the spectroscopic characteristics of this electron transport protein without requiring the classic rubredoxin protein fold.
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Koebke KJ, Yu F, Salerno E, Van Stappen C, Tebo AG, Penner-Hahn JE, Pecoraro VL. Modifying the Steric Properties in the Second Coordination Sphere of Designed Peptides Leads to Enhancement of Nitrite Reductase Activity. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201712757] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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42
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Koebke KJ, Yu F, Salerno E, Van Stappen C, Tebo AG, Penner-Hahn JE, Pecoraro VL. Modifying the Steric Properties in the Second Coordination Sphere of Designed Peptides Leads to Enhancement of Nitrite Reductase Activity. Angew Chem Int Ed Engl 2018; 57:3954-3957. [PMID: 29316146 DOI: 10.1002/anie.201712757] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Indexed: 11/10/2022]
Abstract
Protein design is a useful strategy to interrogate the protein structure-function relationship. We demonstrate using a highly modular 3-stranded coiled coil (TRI-peptide system) that a functional type 2 copper center exhibiting copper nitrite reductase (NiR) activity exhibits the highest homogeneous catalytic efficiency under aqueous conditions for the reduction of nitrite to NO and H2 O. Modification of the amino acids in the second coordination sphere of the copper center increases the nitrite reductase activity up to 75-fold compared to previously reported systems. We find also that steric bulk can be used to enforce a three-coordinate CuI in a site, which tends toward two-coordination with decreased steric bulk. This study demonstrates the importance of the second coordination sphere environment both for controlling metal-center ligation and enhancing the catalytic efficiency of metalloenzymes and their analogues.
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Nguyen TN, Chow CY, Eliseeva SV, Trivedi ER, Kampf JW, Martinić I, Petoud S, Pecoraro VL. Cover Feature: One-Step Assembly of Visible and Near-Infrared Emitting Metallacrown Dimers Using a Bifunctional Linker (Chem. Eur. J. 5/2018). Chemistry 2018. [DOI: 10.1002/chem.201705225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Lutter JC, Zaleski CM, Pecoraro VL. Metallacrowns: Supramolecular Constructs With Potential in Extended Solids, Solution-State Dynamics, Molecular Magnetism, and Imaging. ADVANCES IN INORGANIC CHEMISTRY 2018. [DOI: 10.1016/bs.adioch.2017.11.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Cabral ACS, Jakovleska J, Deb A, Penner-Hahn JE, Pecoraro VL, Freisinger E. Further insights into the metal ion binding abilities and the metalation pathway of a plant metallothionein from Musa acuminata. J Biol Inorg Chem 2018; 23:91-107. [PMID: 29218632 PMCID: PMC5756683 DOI: 10.1007/s00775-017-1513-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 11/07/2017] [Indexed: 10/18/2022]
Abstract
The superfamily of metallothioneins (MTs) combines a diverse group of metalloproteins, sharing the characteristics of rather low molecular weight and high cysteine content. The latter provides MTs with the capability to coordinate thiophilic metal ions, in particular those with a d 10 electron configuration. The sub-family of plant MT3 proteins is only poorly characterized and there is a complete lack of three-dimensional structure information. Building upon our previous results on the Musa acuminata MT3 (musMT3) protein, the focus of the present work is to understand the metal cluster formation process, the role of the single histidine residue present in musMT3, and the metal ion binding affinity. We concentrate our efforts on the coordination of ZnII and CdII ions, using CoII as a spectroscopic probe for ZnII binding. The overall protein-fold is analysed with a combination of limited proteolytic digestion, mass spectrometry, and dynamic light scattering. Histidine coordination of metal ions is probed with extended X-ray absorption fine structure spectroscopy and CoII titration experiments. Initial experiments with isothermal titration calorimetry provide insights into the thermodynamics of metal ion binding.
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Nguyen TN, Chow CY, Eliseeva SV, Trivedi ER, Kampf JW, Martinić I, Petoud S, Pecoraro VL. One‐Step Assembly of Visible and Near‐Infrared Emitting Metallacrown Dimers Using a Bifunctional Linker. Chemistry 2017; 24:1031-1035. [DOI: 10.1002/chem.201703911] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Indexed: 12/21/2022]
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Martinić I, Eliseeva SV, Nguyen TN, Foucher F, Gosset D, Westall F, Pecoraro VL, Petoud S. Near-infrared luminescent metallacrowns for combined in vitro cell fixation and counter staining. Chem Sci 2017; 8:6042-6050. [PMID: 28989634 PMCID: PMC5625569 DOI: 10.1039/c7sc01872j] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 06/21/2017] [Indexed: 01/01/2023] Open
Abstract
Cell fixation is an essential approach for preserving cell morphology, allowing the targeting and labelling of biomolecules with fluorescent probes. One of the key requirements for more efficient fluorescent labelling is the preservation of cell morphology, which usually requires a combination of several fixation techniques. In addition, the use of a counter stain is often essential to improve the contrast of the fluorescent probes. Current agents possess significant limitations, such as low resistance toward photobleaching and sensitivity to changes in the microenvironment. Luminescent Ln3+ 'encapsulated sandwich' metallacrowns (MCs) overcome these drawbacks and offer complementary advantages. In particular, they emit sharp emission bands, possess a large difference between excitation and emission wavelengths and do not photobleach. Herein, MCs formed with pyrazinehydroxamic acid (Ln3+[Zn(ii)MCpyzHA], Ln3+ = Yb, Nd) were used, combined with near-infrared (NIR) counter staining and fixation agents for HeLa cells upon an initial five minute exposure to UV-A light. The validity and quality of the cell fixation were assessed with Raman spectroscopy. Analysis of the NIR luminescence properties of these MCs was performed under different experimental conditions, including in a suspension of stained cells. Moreover, the high emission intensity of Ln3+[Zn(ii)MCpyzHA] in the NIR region allows these MCs to be used for imaging with standard CCD cameras installed on routine fluorescence microscopes. Finally, the NIR-emitting Ln3+[Zn(ii)MCpyzHA] compounds combine, within a single molecule, features such as cell fixation and staining abilities, good photostability and minimal sensitivity of the emission bands to the local microenvironment, and they are highly promising for establishing the next generation of imaging agents with a single biodistribution.
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Martinić I, Eliseeva SV, Nguyen TN, Pecoraro VL, Petoud S. Near-Infrared Optical Imaging of Necrotic Cells by Photostable Lanthanide-Based Metallacrowns. J Am Chem Soc 2017; 139:8388-8391. [DOI: 10.1021/jacs.7b01587] [Citation(s) in RCA: 95] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Ruckthong L, Peacock AFA, Pascoe CE, Hemmingsen L, Stuckey JA, Pecoraro VL. d-Cysteine Ligands Control Metal Geometries within De Novo Designed Three-Stranded Coiled Coils. Chemistry 2017; 23:8232-8243. [PMID: 28384393 DOI: 10.1002/chem.201700660] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2017] [Indexed: 12/31/2022]
Abstract
Although metal ion binding to naturally occurring l-amino acid proteins is well documented, understanding the impact of the opposite chirality (d-)amino acids on the structure and stereochemistry of metals is in its infancy. We examine the effect of a d-configuration cysteine within a designed l-amino acid three-stranded coiled coil in order to enforce a precise coordination number on a metal center. The d chirality does not alter the native fold, but the side-chain re-orientation modifies the sterics of the metal binding pocket. l-Cys side chains within the coiled-coil structure have previously been shown to rotate substantially from their preferred positions in the apo structure to create a binding site for a tetra-coordinate metal ion. However, here we show by X-ray crystallography that d-Cys side chains are preorganized within a suitable geometry to bind such a ligand. This is confirmed by comparison of the structure of ZnII Cl(CSL16D C)32- to the published structure of ZnII (H2 O)(GRAND-CSL12AL16L C)3- . Moreover, spectroscopic analysis indicates that the CdII geometry observed by using l-Cys ligands (a mixture of three- and four-coordinate CdII ) is altered to a single four-coordinate species when d-Cys is present. This work opens a new avenue for the control of the metal site environment in man-made proteins, by simply altering the binding ligand with its mirror-imaged d configuration. Thus, the use of non-coded amino acids in the coordination sphere of a metal promises to be a powerful tool for controlling the properties of future metalloproteins.
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Sgarlata C, Giuffrida A, Trivedi ER, Pecoraro VL, Arena G. Anion Encapsulation Drives the Formation of Dimeric Gd III[15-metallacrown-5] 3+ Complexes in Aqueous Solution. Inorg Chem 2017; 56:4771-4774. [PMID: 28414219 DOI: 10.1021/acs.inorgchem.6b03043] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Metallacrown complexes capable of sequestering dianions, as shown in the solid state, also exist in aqueous solution at neutral pH, as demonstrated by calorimetric and mass spectrometric data. The driving forces for the formation of these dimeric complexes in solution strongly depend on the chain length of the guest rather than its degree of unsaturation.
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