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Declerck K, Savić ND, Moussawi MA, Seno C, Pokratath R, De Roo J, Parac-Vogt TN. Molecular Insights into Sequence-Specific Protein Hydrolysis by a Soluble Zirconium-Oxo Cluster Catalyst. J Am Chem Soc 2024. [PMID: 38621177 DOI: 10.1021/jacs.4c01324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/17/2024]
Abstract
The development of catalysts for controlled fragmentation of proteins is a critical undertaking in modern proteomics and biotechnology. {Zr6O8}-based metal-organic frameworks (MOFs) have emerged as promising candidates for catalysis of peptide bond hydrolysis due to their high reactivity, stability, and recyclability. However, emerging evidence suggests that protein hydrolysis mainly occurs on the MOF surface, thereby questioning the need for their highly porous 3D nature. In this work, we show that the discrete and water-soluble [Zr6O4(OH)4(CH3CO2)8(H2O)2Cl3]+ (Zr6) metal-oxo cluster (MOC), which is based on the same hexamer motif found in various {Zr6O8}-based MOFs, shows excellent activity toward selective hydrolysis of equine skeletal muscle myoglobin. Compared to related Zr-MOFs, Zr6 exhibits superior reactivity, with near-complete protein hydrolysis after 24 h of incubation at 60 °C, producing seven selective fragments with a molecular weight in the range of 3-15 kDa, which are of ideal size for middle-down proteomics. The high solubility and molecular nature of Zr6 allow detailed solution-based mechanistic/interaction studies, which revealed that cluster-induced protein unfolding is a key step that facilitates hydrolysis. A combination of multinuclear nuclear magnetic resonance spectroscopy and pair distribution function analysis provided insight into the speciation of Zr6 and the ligand exchange processes occurring on the surface of the cluster, which results in the dimerization of two Zr6 clusters via bridging oxygen atoms. Considering the relevance of discrete Zr-oxo clusters as building blocks of MOFs, the molecular-level understanding reported in this work contributes to the further development of novel catalysts based on Zr-MOFs.
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Affiliation(s)
| | - Nada D Savić
- Department of Chemistry, KU Leuven, 3001 Leuven, Belgium
| | | | - Carlotta Seno
- Department of Chemistry, University of Basel, 4058 Basel, Switzerland
| | - Rohan Pokratath
- Department of Chemistry, University of Basel, 4058 Basel, Switzerland
| | - Jonathan De Roo
- Department of Chemistry, University of Basel, 4058 Basel, Switzerland
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2
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Salazar Marcano DE, Savić ND, Declerck K, Abdelhameed SAM, Parac-Vogt TN. Reactivity of metal-oxo clusters towards biomolecules: from discrete polyoxometalates to metal-organic frameworks. Chem Soc Rev 2024; 53:84-136. [PMID: 38015569 DOI: 10.1039/d3cs00195d] [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: 11/29/2023]
Abstract
Metal-oxo clusters hold great potential in several fields such as catalysis, materials science, energy storage, medicine, and biotechnology. These nanoclusters of transition metals with oxygen-based ligands have also shown promising reactivity towards several classes of biomolecules, including proteins, nucleic acids, nucleotides, sugars, and lipids. This reactivity can be leveraged to address some of the most pressing challenges we face today, from fighting various diseases, such as cancer and viral infections, to the development of sustainable and environmentally friendly energy sources. For instance, metal-oxo clusters and related materials have been shown to be effective catalysts for biomass conversion into renewable fuels and platform chemicals. Furthermore, their reactivity towards biomolecules has also attracted interest in the development of inorganic drugs and bioanalytical tools. Additionally, the structural versatility of metal-oxo clusters allows for the efficiency and selectivity of the biomolecular reactions they promote to be readily tuned, thereby providing a pathway towards reaction optimization. The properties of the catalyst can also be improved through incorporation into solid supports or by linking metal-oxo clusters together to form Metal-Organic Frameworks (MOFs), which have been demonstrated to be powerful heterogeneous catalysts. Therefore, this review aims to provide a comprehensive and critical analysis of the state of the art on biomolecular transformations promoted by metal-oxo clusters and their applications, with a particular focus on structure-activity relationships.
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Affiliation(s)
| | - Nada D Savić
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium.
| | - Kilian Declerck
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium.
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Salazar Marcano D, Savić ND, Abdelhameed SAM, de Azambuja F, Parac-Vogt TN. Exploring the Reactivity of Polyoxometalates toward Proteins: From Interactions to Mechanistic Insights. JACS AU 2023; 3:978-990. [PMID: 37124292 PMCID: PMC10131212 DOI: 10.1021/jacsau.3c00011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 01/31/2023] [Accepted: 02/01/2023] [Indexed: 05/03/2023]
Abstract
The latest advances in the study of the reactivity of metal-oxo clusters toward proteins showcase how fundamental insights obtained so far open new opportunities in biotechnology and medicine. In this Perspective, these studies are discussed through the lens of the reactivity of a family of soluble anionic metal-oxo nanoclusters known as polyoxometalates (POMs). POMs act as catalysts in a wide range of reactions with several different types of biomolecules and have promising therapeutic applications due to their antiviral, antibacterial, and antitumor activities. However, the lack of a detailed understanding of the mechanisms behind biochemically relevant reactions-particularly with complex biological systems such as proteins-still hinders further developments. Hence, in this Perspective, special attention is given to reactions of POMs with peptides and proteins showcasing a molecular-level understanding of the reaction mechanism. In doing so, we aim to highlight both existing limitations and promising directions of future research on the reactivity of metal-oxo clusters toward proteins and beyond.
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4
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Abdelhameed SAM, de Azambuja F, Vasović T, Savić ND, Ćirković Veličković T, Parac-Vogt TN. Regioselective protein oxidative cleavage enabled by enzyme-like recognition of an inorganic metal oxo cluster ligand. Nat Commun 2023; 14:486. [PMID: 36717594 PMCID: PMC9887005 DOI: 10.1038/s41467-023-36085-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 01/16/2023] [Indexed: 02/01/2023] Open
Abstract
Oxidative modifications of proteins are key to many applications in biotechnology. Metal-catalyzed oxidation reactions efficiently oxidize proteins but with low selectivity, and are highly dependent on the protein surface residues to direct the reaction. Herein, we demonstrate that discrete inorganic ligands such as polyoxometalates enable an efficient and selective protein oxidative cleavage. In the presence of ascorbate (1 mM), the Cu-substituted polyoxometalate K8[Cu2+(H2O)(α2-P2W17O61)], (CuIIWD, 0.05 mM) selectively cleave hen egg white lysozyme under physiological conditions (pH =7.5, 37 °C) producing only four bands in the gel electropherogram (12.7, 11, 10, and 5 kDa). Liquid chromatography/mass spectrometry analysis reveals a regioselective cleavage in the vicinity of crystallographic CuIIWD/lysozyme interaction sites. Mechanistically, polyoxometalate is critical to position the Cu at the protein surface and limit the generation of oxidative species to the proximity of binding sites. Ultimately, this study outlines the potential of discrete, designable metal oxo clusters as catalysts for the selective modification of proteins through radical mechanisms under non-denaturing conditions.
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Affiliation(s)
| | | | - Tamara Vasović
- Center of Excellence for Molecular Food Sciences & Department of Biochemistry, University of Belgrade - Faculty of Chemistry, Belgrade, Serbia
| | - Nada D Savić
- KU Leuven, Department of Chemistry, Celestijnenlaan 200F, 3001, Leuven, Belgium
| | - Tanja Ćirković Veličković
- Center of Excellence for Molecular Food Sciences & Department of Biochemistry, University of Belgrade - Faculty of Chemistry, Belgrade, Serbia.,Ghent University Global Campus, Yeonsu-gu, Incheon, South Korea.,Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium.,Serbian Academy of Sciences and Arts, Belgrade, Serbia
| | - Tatjana N Parac-Vogt
- KU Leuven, Department of Chemistry, Celestijnenlaan 200F, 3001, Leuven, Belgium.
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Salazar Marcano DE, Lentink S, Moussawi MA, Parac-Vogt TN. Solution Dynamics of Hybrid Anderson-Evans Polyoxometalates. Inorg Chem 2021; 60:10215-10226. [PMID: 33881856 DOI: 10.1021/acs.inorgchem.1c00511] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Understanding the stability and speciation of metal-oxo clusters in solution is essential for many of their applications in different areas. In particular, hybrid organic-inorganic polyoxometalates (HPOMs) have been attracting increasing attention as they combine the complementary properties of organic ligands and metal-oxygen nanoclusters. Nevertheless, the speciation and solution behavior of HPOMs have been scarcely investigated. Hence, in this work, a series of HPOMs based on the archetypical Anderson-Evans structure, δ-[MnMo6O18{(OCH2)3C-R}2]3-, with different functional groups (R = -NH2, -CH3, -NHCOCH2Cl, -N═CH(2-C5H4N) {pyridine; -Pyr}, and -NHCOC9H15N2OS {biotin; -Biot}) and countercations (tetrabutylammonium {TBA}, Li, Na, and K) were synthesized, and their solution behavior was studied in detail. In aqueous solutions, decomposition of HPOMs into the free organic ligand, [MoO4]2-, and free Mn3+ was observed over time and was shown to be highly dependent on the pH, temperature, and nature of the ligand functional group but largely independent of ionic strength or the nature of the countercation. Furthermore, hydrolysis of the amide and imine bonds often present in postfunctionalized HPOMs was also observed. Hence, HPOMs were shown to exhibit highly dynamic behavior in solution, which needs to be carefully considered when designing HPOMs, particularly for biological applications.
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Affiliation(s)
| | - Sarah Lentink
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
| | - Mhamad A Moussawi
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
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Azambuja FD, Moons J, Parac-Vogt TN. The Dawn of Metal-Oxo Clusters as Artificial Proteases: From Discovery to the Present and Beyond. Acc Chem Res 2021; 54:1673-1684. [PMID: 33600141 DOI: 10.1021/acs.accounts.0c00666] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The selective cleavage of peptide bonds in proteins is of paramount importance in many areas of the biological and medical sciences, playing a key role in protein structure/function/folding analysis, protein engineering, and targeted proteolytic drug design. Current applications that depend on selective protein hydrolysis largely rely on costly proteases such as trypsin, which are sensitive to the pH, ionic strength, and temperature conditions. Moreover, >95% of peptides deposited in databases are generated from trypsin digests, restricting the information within the analyzed proteomes. On the other hand, harsh and toxic chemical reagents such as BrCN are very active but cause permanent modifications of certain amino acid residues. Consequently, transition-metal complexes have emerged as smooth and selective artificial proteases owing to their ability to provide larger fragments and complementary structural information. In the past decade, our group has discovered the unique protease activity of diverse metal-oxo clusters (MOC) and pioneered a distinctive approach to the development of selective artificial proteases. In contrast to classical coordination complexes which often depend on amino acid side chains to control the regioselectivity, the selectivity profile of MOCs is determined by a complex combination of structural factors, such as the protein surface charge, metal coordination to specific side chains, and hydrogen bonding between the protein surface and the MOC scaffold.In this Account, we present a critical overview of our detailed kinetic, spectroscopic, and crystallographic studies in MOC-assisted peptide bond hydrolysis, from its origins to the current rational and detailed mechanistic understanding. To this end, reactivity trends related to the structure and properties of MOCs based on the hydrolysis of small model peptides and key structural aspects governing the selectivity of protein hydrolysis are presented. Finally, our endeavors in seeking the next generation of heterogeneous MOC-based proteases are briefly discussed by embedding MOCs in metal-organic frameworks or using them as discrete nanoclusters in the development of artificial protease-like materials (i.e., nanozymes). The deep and comprehensive understanding sought experimentally and theoretically over the years in aqueous systems with intrinsic polar and charged substrates provides a unique view of the reactivity between inorganic moieties and biomolecules, thereby broadly impacting several different fields (e.g., catalysis in biochemistry, inorganic chemistry, and organic chemistry).
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Affiliation(s)
| | - Jens Moons
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
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Mahesh S, Tang KC, Raj M. Amide Bond Activation of Biological Molecules. Molecules 2018; 23:E2615. [PMID: 30322008 PMCID: PMC6222841 DOI: 10.3390/molecules23102615] [Citation(s) in RCA: 103] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Revised: 10/09/2018] [Accepted: 10/09/2018] [Indexed: 12/02/2022] Open
Abstract
Amide bonds are the most prevalent structures found in organic molecules and various biomolecules such as peptides, proteins, DNA, and RNA. The unique feature of amide bonds is their ability to form resonating structures, thus, they are highly stable and adopt particular three-dimensional structures, which, in turn, are responsible for their functions. The main focus of this review article is to report the methodologies for the activation of the unactivated amide bonds present in biomolecules, which includes the enzymatic approach, metal complexes, and non-metal based methods. This article also discusses some of the applications of amide bond activation approaches in the sequencing of proteins and the synthesis of peptide acids, esters, amides, and thioesters.
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Affiliation(s)
- Sriram Mahesh
- Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849, USA.
| | - Kuei-Chien Tang
- Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849, USA.
| | - Monika Raj
- Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849, USA.
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Quanten T, De Mayaer T, Shestakova P, Parac-Vogt TN. Selectivity and Reactivity of Zr IV and Ce IV Substituted Keggin Type Polyoxometalates Toward Cytochrome c in Surfactant Solutions. Front Chem 2018; 6:372. [PMID: 30211153 PMCID: PMC6121075 DOI: 10.3389/fchem.2018.00372] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 08/02/2018] [Indexed: 12/15/2022] Open
Abstract
In this paper we investigate the effect of three different types of surfactants, on the hydrolysis of Cytochrome c (Cyt c), a predominantly α helical protein containing a heme group, promoted by [Ce(α PW11O39)2]10- (CeK) and [Zr(α PW11O39)2]10- (ZrK) polyoxometalates. In the presence of SDS, Zw3 12, or CHAPS surfactants, which are commonly used for solubilizing hydrophobic proteins, the specificity of CeK or ZrK toward hydrolysis of Cyt c does not change. However, the hydrolysis rate of Cyt c by CeK was increased in the presence of SDS, but decreased in the presence of CHAPS, and was nearly inhibited in the presence of Zw3 12. The Circular dichroism and Tryptophan fluorescence spectroscopy have shown that the structural changes in Cyt c caused by surfactants are similar to those caused by POMs, hence the same specificity in the absence or presence of surfactants was observed. The results also indicate that for Cyt c hydrolysis to occur, large unfolding of the protein is needed in order to accommodate the POMs. While SDS readily unfolds Cyt c, the protein remains largely folded in the presence of CHAPS and Zw3 12. Addition of POMs to Cyt c solutions in CHAPS results in unfolding of the structure allowing the interaction with POMs to occur and results in protein hydrolysis. Zw3 12, however, locks Cyt c in a conformation that resists unfolding upon addition of POM, and therefore results in nearly complete inhibition of protein hydrolysis.
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Affiliation(s)
- Thomas Quanten
- Laboratory of Bio-Inorganic Chemistry, Department of Chemistry, KU Leuven, Leuven, Belgium
| | - Tessa De Mayaer
- Laboratory of Bio-Inorganic Chemistry, Department of Chemistry, KU Leuven, Leuven, Belgium
| | - Pavletta Shestakova
- NMR Centre, Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - Tatjana N Parac-Vogt
- Laboratory of Bio-Inorganic Chemistry, Department of Chemistry, KU Leuven, Leuven, Belgium
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Sap A, Vandebroek L, Goovaerts V, Martens E, Proost P, Parac-Vogt TN. Highly Selective and Tunable Protein Hydrolysis by a Polyoxometalate Complex in Surfactant Solutions: A Step toward the Development of Artificial Metalloproteases for Membrane Proteins. ACS OMEGA 2017; 2:2026-2033. [PMID: 30023653 PMCID: PMC6044816 DOI: 10.1021/acsomega.7b00168] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 04/28/2017] [Indexed: 05/17/2023]
Abstract
This study represents the first example of protein hydrolysis at pH = 7.4 and 60 °C by a metal-substituted polyoxometalate (POM) in the presence of a zwitterionic surfactant. Edman degradation results show that in the presence of 0.5% w/v 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) detergent, a Zr(IV)-substituted Wells-Dawson-type POM, K15H[Zr(α2-P2W17O61)2]·25H2O (Zr1-WD2), selectively hydrolyzes human serum albumin exclusively at peptide bonds involving Asp or Glu residues, which contain carboxyl groups in their side chains. The selectivity and extent of protein cleavage are tuned by the CHAPS surfactant by an unfolding mechanism that provides POM access to the hydrolyzed peptide bonds.
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Affiliation(s)
- Annelies Sap
- Department
of Chemistry, KU Leuven, Celestijnenlaan 200F, Box 2404, 3001 Leuven, Belgium
| | - Laurens Vandebroek
- Department
of Chemistry, KU Leuven, Celestijnenlaan 200F, Box 2404, 3001 Leuven, Belgium
| | - Vincent Goovaerts
- Department
of Chemistry, KU Leuven, Celestijnenlaan 200F, Box 2404, 3001 Leuven, Belgium
| | - Erik Martens
- Department
of Microbiology and Immunology, KU Leuven, Herestraat 49,
Box 1042, 3000 Leuven, Belgium
| | - Paul Proost
- Department
of Microbiology and Immunology, KU Leuven, Herestraat 49,
Box 1042, 3000 Leuven, Belgium
| | - Tatjana N. Parac-Vogt
- Department
of Chemistry, KU Leuven, Celestijnenlaan 200F, Box 2404, 3001 Leuven, Belgium
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10
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Metal assisted peptide bond hydrolysis: Chemistry, biotechnology and toxicological implications. Coord Chem Rev 2016. [DOI: 10.1016/j.ccr.2016.02.009] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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11
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Quanten T, Shestakova P, Van Den Bulck D, Kirschhock C, Parac-Vogt TN. Interaction Study and Reactivity of Zr(IV) -Substituted Wells-Dawson Polyoxometalate towards Hydrolysis of Peptide Bonds in Surfactant Solutions. Chemistry 2016; 22:3775-84. [PMID: 26833582 DOI: 10.1002/chem.201503976] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Indexed: 11/09/2022]
Abstract
The interaction between the 1:2 Zr(IV) :Wells-Dawson complex, K15 H[Zr(α2 -P2 W17 O61 )2] (1), and a range of surfactants was studied in detail with the aim of developing metal-substituted POMs as potential artificial proteases for membrane proteins. The surfactants include the positively charged cetyl(trimethyl)ammonium bromide (CTAB), the negatively charged sodium dodecyl sulfate (SDS), the neutral Triton X-100 (TX-100), and zwitterionic 3-[dodecyl(dimethyl)ammonio]-1-propanesulfonate (Zw3-13) and 3-[dimethyl(3-{[(3α,5β,7α,12α)-3,7,12-trihydroxy-24-oxocholan-24-yl]amino}propyl)ammonio]-1-propanesulfonate (CHAPS). A combination of multinuclear (1)H, (13)C, and (31) P NMR spectroscopy, (1)H diffusion-ordered NMR spectroscopy ((1)H DOSY), and nuclear Overhauser effect spectroscopy (NOESY) was used to examine the interaction between 1 and each surfactant on the molecular level. Cationic surfactant CTAB caused precipitation of 1 due to strong electrostatic interactions, while the anionic SDS and neutral TX-100 surfactants did not exhibit any interaction at neutral pD. (1)H DOSY NMR spectroscopy indicated an interaction between 1 and zwitterionic surfactants Zw3-12 and CHAPS, which occurs via the positively charged ammonium group in the surfactant molecule. In the presence of anionic, neutral, and zwitterionic surfactants, 1 preserves its catalytic activity towards the hydrolysis of the peptide bond in the dipeptide glycyl-l-histidine (GH). The fastest hydrolysis was observed at pD 7.0 and could be rationalized by taking into account pD-dependent speciation of 1 and coordination properties of GH.
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Affiliation(s)
- Thomas Quanten
- Department Of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001, Leuven, Belgium
| | - Pavletta Shestakova
- NMR Laboratory, Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Acad. G. Bontchef Str., B1.9, Sofia, 1113, Bulgaria
| | - Dries Van Den Bulck
- Department Of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001, Leuven, Belgium
| | - Christine Kirschhock
- Centre for Surface Chemistry and Catalysis, KU Leuven, Celestijnenlaan 200F, 3001, Leuven, Belgium
| | - Tatjana N Parac-Vogt
- Department Of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001, Leuven, Belgium.
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Ly HGT, Mihaylov T, Absillis G, Pierloot K, Parac-Vogt TN. Reactivity of Dimeric Tetrazirconium(IV) Wells-Dawson Polyoxometalate toward Dipeptide Hydrolysis Studied by a Combined Experimental and Density Functional Theory Approach. Inorg Chem 2015; 54:11477-92. [PMID: 26599585 DOI: 10.1021/acs.inorgchem.5b02122] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Detailed kinetic studies on the hydrolysis of glycylglycine (Gly-Gly) in the presence of the dimeric tetrazirconium(IV)-substituted Wells-Dawson-type polyoxometalate Na14[Zr4(P2W16O59)2(μ3-O)2(OH)2(H2O)4] · 57H2O (1) were performed by a combination of (1)H, (13)C, and (31)P NMR spectroscopies. The catalyst was shown to be stable under a broad range of reaction conditions. The effect of pD on the hydrolysis of Gly-Gly showed a bell-shaped profile with the fastest hydrolysis observed at pD 7.4. The observed rate constant for the hydrolysis of Gly-Gly at pD 7.4 and 60 °C was 4.67 × 10(-7) s(-1), representing a significant acceleration as compared to the uncatalyzed reaction. (13)C NMR data were indicative for coordination of Gly-Gly to 1 via its amide oxygen and amine nitrogen atoms, resulting in a hydrolytically active complex. Importantly, the effective hydrolysis of a series of Gly-X dipeptides with different X side chain amino acids in the presence of 1 was achieved, and the observed rate constant was shown to be dependent on the volume, chemical nature, and charge of the X amino acid side chain. To give a mechanistic explanation of the observed catalytic hydrolysis of Gly-Gly, a detailed quantum-chemical study was performed. The theoretical results confirmed the nature of the experimentally suggested binding mode in the hydrolytically active complex formed between Gly-Gly and 1. To elucidate the role of 1 in the hydrolytic process, both the uncatalyzed and the polyoxometalate-catalyzed reactions were examined. In the rate-determining step of the uncatalyzed Gly-Gly hydrolysis, a carboxylic oxygen atom abstracts a proton from a solvent water molecule and the nascent OH nucleophile attacks the peptide carbon atom. Analogous general-base activity of the free carboxylic group was found to take place also in the case of polyoxometalate-catalyzed hydrolysis as the main catalytic effect originates from the -C═O···Zr(IV) binding.
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Affiliation(s)
- Hong Giang T Ly
- Laboratory of Bioinorganic Chemistry and ‡Laboratory of Computational Coordination Chemistry, Department of Chemistry, Katholieke Universiteit Leuven , Celestijnenlaan 200F, 3001 Leuven, Belgium
| | - Tzvetan Mihaylov
- Laboratory of Bioinorganic Chemistry and ‡Laboratory of Computational Coordination Chemistry, Department of Chemistry, Katholieke Universiteit Leuven , Celestijnenlaan 200F, 3001 Leuven, Belgium
| | - Gregory Absillis
- Laboratory of Bioinorganic Chemistry and ‡Laboratory of Computational Coordination Chemistry, Department of Chemistry, Katholieke Universiteit Leuven , Celestijnenlaan 200F, 3001 Leuven, Belgium
| | - Kristine Pierloot
- Laboratory of Bioinorganic Chemistry and ‡Laboratory of Computational Coordination Chemistry, Department of Chemistry, Katholieke Universiteit Leuven , Celestijnenlaan 200F, 3001 Leuven, Belgium
| | - Tatjana N Parac-Vogt
- Laboratory of Bioinorganic Chemistry and ‡Laboratory of Computational Coordination Chemistry, Department of Chemistry, Katholieke Universiteit Leuven , Celestijnenlaan 200F, 3001 Leuven, Belgium
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13
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Goovaerts V, Stroobants K, Absillis G, Parac-Vogt TN. Eu(III) luminescence and tryptophan fluorescence spectroscopy as a tool for understanding interactions between hen egg white lysozyme and metal-substituted Keggin type polyoxometalates. J Inorg Biochem 2015; 150:72-80. [PMID: 25870147 DOI: 10.1016/j.jinorgbio.2015.03.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 03/17/2015] [Accepted: 03/26/2015] [Indexed: 01/11/2023]
Abstract
The interaction between the lacunary Keggin K7PW11O39, the Eu(III)-substituted Keggin K4EuPW11O39 (Eu-Keggin) and the Ce(IV)-substituted Keggin [Me2NH2]10[Ce(PW11O39)2] (Ce-Keggin) polyoxometalates (POMs), and the proteins hen egg white lysozyme (HEWL) and the structurally homologous α-lactalbumin (α-LA) was studied by steady state and time-resolved Eu(III) luminescence and tryptophan (Trp) fluorescence spectroscopy. The excitation spectrum of Eu-Keggin at lower concentrations ([Eu-Keggin]<100 μM) is dominated by a ligand-to-metal charge transfer band (291 nm). For higher concentrations ([Eu-Keggin]>250 μM) the (5)L6←(7)F0 transition becomes the most intense peak. In the absence of protein, the number of coordinated water molecules to the Eu(III) centre of Eu-Keggin is 4, indicating a 1:1 Eu(III):POM species. In the presence of phosphate buffer this number linearly decreases from 4 to 2 upon increasing phosphate buffer concentration. Upon addition of HEWL, there are no coordinated water molecules, suggesting interaction between Eu-Keggin and the protein surface. In addition, this interaction results in a more than threefold increase of the hypersensitive (5)D0→(7)F2 transition for the Eu-Keggin/HEWL mixture. The calculated association constant amounted to 2.2×10(2) M(-1) for the Eu-Keggin/HEWL complex. Tryptophan fluorescence quenching studies were performed and the quenching constants were calculated to be 9.1×10(4) M(-1), 4×10(4) M(-1) and 4.1×10(5) M(-1) for the lacunary Keggin/HEWL, the Eu-Keggin/HEWL and the Ce-Keggin/HEWL complexes, respectively. The number of bound POM molecules to HEWL was 1.04 for the lacunary Keggin POM, and 1.0 for Eu-Keggin, indicating the formation of a 1:1 POM/HEWL complex. The value of 1.38 for Ce-Keggin might indicate a transition from 1:1 to 1:2 interaction.
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Affiliation(s)
- Vincent Goovaerts
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
| | - Karen Stroobants
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
| | - Gregory Absillis
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
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Stroobants K, Goovaerts V, Absillis G, Bruylants G, Moelants E, Proost P, Parac-Vogt TN. Molecular origin of the hydrolytic activity and fixed regioselectivity of a Zr(IV) -substituted polyoxotungstate as artificial protease. Chemistry 2014; 20:9567-77. [PMID: 24958622 DOI: 10.1002/chem.201402683] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Indexed: 01/07/2023]
Abstract
A multitechnique approach has been applied in order to identify the thermodynamic and kinetic parameters related to the regioselective hydrolysis of human serum albumin (HSA) promoted by the Wells-Dawson polyoxometalate (POM), K15 H[Zr(α2 -P2 W17 O61 )2 ]. Isothermal titration calorimetry (ITC) studies indicate that up to four POM molecules interact with HSA. While the first interaction site is characterized by a 1:1 binding and an affinity constant of 2×10(8) M(-1) , the three remaining sites are characterized by a lower global affinity constant of 7×10(5) M(-1) . The higher affinity constant at the first site is in accordance with a high quenching constant of 2.2×10(8) M(-1) obtained for fluorescence quenching of the Trp214 residue located in the only positively charged cleft of HSA, in the presence of K15 H[Zr(α2 -P2 W17 O61 )2 ]. In addition, Eu(III) luminescence experiments with an Eu(III) -substituted POM analogue have shown the replacement of water molecules in the first coordination sphere of Eu(III) due to binding of the metal ion to amino acid side chain residues of HSA. All three interaction studies are in accordance with a stronger POM dominated binding at the positive cleft on the one hand, and interaction mainly governed by metal anchoring at the three remaining positions, on the other hand. Hydrolysis experiments in the presence of K15 H[Zr(α2 -P2 W17 O61 )2 ] have demonstrated regioselective cleavage of HSA at the Arg114Leu115, Ala257Asp258, Lys313Asp314 or Cys392Glu393 peptide bonds. This is in agreement with the interaction studies as the Arg114Leu115 peptide bond is located in the positive cleft of HSA and the three remaining peptide bonds are each located near an upstream acidic residue, which can be expected to coordinate to the metal ion. A detailed kinetic study has evidenced the formation of additional fragments upon prolonged reaction times. Edman degradation of the additional reaction products has shown that these fragments result from further hydrolysis at the initially observed cleavage positions, indicating a fixed selectivity for K15 H[Zr(α2 -P2 W17 O61 )2 ].
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Affiliation(s)
- Karen Stroobants
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven (Belgium)
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