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Recabarren R, Osorio EH, Caballero J, Tuñón I, Alzate-Morales JH. Mechanistic insights into the phosphoryl transfer reaction in cyclin-dependent kinase 2: A QM/MM study. PLoS One 2019; 14:e0215793. [PMID: 31483779 PMCID: PMC6726203 DOI: 10.1371/journal.pone.0215793] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 08/19/2019] [Indexed: 12/18/2022] Open
Abstract
Cyclin-dependent kinase 2 (CDK2) is an important member of the CDK family exerting its most important function in the regulation of the cell cycle. It catalyzes the transfer of the gamma phosphate group from an ATP (adenosine triphosphate) molecule to a Serine/Threonine residue of a peptide substrate. Due to the importance of this enzyme, and protein kinases in general, a detailed understanding of the reaction mechanism is desired. Thus, in this work the phosphoryl transfer reaction catalyzed by CDK2 was revisited and studied by means of hybrid quantum mechanics/molecular mechanics (QM/MM) calculations. Our results suggest that the base-assisted mechanism is preferred over the substrate-assisted pathway when one Mg2+ is present in the active site, in agreement with a previous theoretical study. The base-assisted mechanism resulted to be dissociative, with a potential energy barrier of 14.3 kcal/mol, very close to the experimental derived value. An interesting feature of the mechanism is the proton transfer from Lys129 to the phosphoryl group at the second transition state, event that could be helping in neutralizing the charge on the phosphoryl group upon the absence of a second Mg2+ ion. Furthermore, important insights into the mechanisms in terms of bond order and charge analysis were provided. These descriptors helped to characterize the synchronicity of bond forming and breaking events, and to characterize charge transfer effects. Local interactions at the active site are key to modulate the charge distribution on the phosphoryl group and therefore alter its reactivity.
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Affiliation(s)
- Rodrigo Recabarren
- Centro de Bioinformática, Simulación y Modelado (CBSM), Facultad de Ingeniería, Universidad de Talca, Talca, Chile
| | - Edison H. Osorio
- Facultad de Ciencias Naturales y Matemáticas, Universidad de Ibagué, Ibagué, Colombia
| | - Julio Caballero
- Centro de Bioinformática, Simulación y Modelado (CBSM), Facultad de Ingeniería, Universidad de Talca, Talca, Chile
| | - Iñaki Tuñón
- Departament de Química Física, Universitat de Valencia, Valencia, Spain
- * E-mail: (JAM); (IT)
| | - Jans H. Alzate-Morales
- Centro de Bioinformática, Simulación y Modelado (CBSM), Facultad de Ingeniería, Universidad de Talca, Talca, Chile
- * E-mail: (JAM); (IT)
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2
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Murillo-López J, Zinovjev K, Pereira H, Caniuguir A, Garratt R, Babul J, Recabarren R, Alzate-Morales J, Caballero J, Tuñón I, Cabrera R. Studying the phosphoryl transfer mechanism of the E. coli phosphofructokinase-2: from X-ray structure to quantum mechanics/molecular mechanics simulations. Chem Sci 2019; 10:2882-2892. [PMID: 30996866 PMCID: PMC6429617 DOI: 10.1039/c9sc00094a] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 01/24/2019] [Indexed: 12/31/2022] Open
Abstract
Phosphofructokinases catalyze the ATP-dependent phosphorylation of fructose-6-phosphate and they are highly regulated.
Phosphofructokinases (Pfks) catalyze the ATP-dependent phosphorylation of fructose-6-phosphate (F6P) and they are regulated in a wide variety of organisms. Although numerous aspects of the kinetics and regulation have been characterized for Pfks, the knowledge about the mechanism of the phosphoryl transfer reaction and the transition state lags behind. In this work, we describe the X-ray crystal structure of the homodimeric Pfk-2 from E. coli, which contains products in one site and reactants in the other, as well as an additional ATP molecule in the inhibitory allosteric site adjacent to the reactants. This complex was previously predicted when studying the kinetic mechanism of ATP inhibition. After removing the allosteric ATP, molecular dynamic (MD) simulations revealed conformational changes related to domain packing, as well as stable interactions of Lys27 and Asp256 with donor (ATP) and acceptor (fructose-6-) groups, and of Asp166 with Mg2+. The phosphoryl transfer reaction mechanism catalyzed by Pfk-2 was investigated through Quantum Mechanics/Molecular Mechanics (QM/MM) simulations using a combination of the string method and a path-collective variable for the exploration of its free energy surface. The calculated activation free energies showed that a dissociative mechanism, occurring with a metaphosphate intermediate formation followed by a proton transfer to Asp256, is more favorable than an associative one. The structural analysis reveals the role of Asp256 acting as a catalytic base and Lys27 stabilizing the transition state of the dissociative mechanism.
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Affiliation(s)
- Juliana Murillo-López
- Centro de Bioinformática y Simulación Molecular (CBSM) , Facultad de Ingeniería , Universidad de Talca , 1 Poniente 1141 , Talca , Chile .
| | - Kirill Zinovjev
- Departament de Química Física , Universitat de València , 46100 Burjassot , Spain .
| | - Humberto Pereira
- Instituto de Física de São Carlos , Universidade de São Paulo , São Paulo , Brazil
| | - Andres Caniuguir
- Departamento de Biología , Facultad de Ciencias , Universidad de Chile , Santiago , Chile .
| | - Richard Garratt
- Instituto de Física de São Carlos , Universidade de São Paulo , São Paulo , Brazil
| | - Jorge Babul
- Departamento de Biología , Facultad de Ciencias , Universidad de Chile , Santiago , Chile .
| | - Rodrigo Recabarren
- Centro de Bioinformática y Simulación Molecular (CBSM) , Facultad de Ingeniería , Universidad de Talca , 1 Poniente 1141 , Talca , Chile .
| | - Jans Alzate-Morales
- Centro de Bioinformática y Simulación Molecular (CBSM) , Facultad de Ingeniería , Universidad de Talca , 1 Poniente 1141 , Talca , Chile .
| | - Julio Caballero
- Centro de Bioinformática y Simulación Molecular (CBSM) , Facultad de Ingeniería , Universidad de Talca , 1 Poniente 1141 , Talca , Chile .
| | - Iñaki Tuñón
- Departament de Química Física , Universitat de València , 46100 Burjassot , Spain .
| | - Ricardo Cabrera
- Departamento de Biología , Facultad de Ciencias , Universidad de Chile , Santiago , Chile .
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3
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Mena-Ulecia K, Gonzalez-Norambuena F, Vergara-Jaque A, Poblete H, Tiznado W, Caballero J. Study of the affinity between the protein kinase PKA and homoarginine-containing peptides derived from kemptide: Free energy perturbation (FEP) calculations. J Comput Chem 2018; 39:986-992. [PMID: 29399821 DOI: 10.1002/jcc.25176] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 12/05/2017] [Accepted: 01/13/2018] [Indexed: 12/28/2022]
Abstract
Protein kinases (PKs) discriminate between closely related sequences that contain serine, threonine, and/or tyrosine residues. Such specificity is defined by the amino acid sequence surrounding the phosphorylatable residue, so that it is possible to identify an optimal recognition motif (ORM) for each PK. The ORM for the protein kinase A (PKA), a well-known member of the PK family, is the sequence RRX(S/T)X, where arginines at the -3 and -2 positions play a key role with respect to the primed phosphorylation site. In this work, differential affinities of PKA for the peptide substrate Kemptide (LRRASLG) and mutants that substitute the arginine residues by the unnatural peptide homoarginine were evaluated through molecular dynamics (MD) and free energy perturbation (FEP) calculations. The FEP study for the homoarginine mutants required previous elaboration of a CHARMM "arginine to homoarginine" (R2B) hybrid topology file which is available in this manuscript as Supporting Information. Mutants substituting the arginine residues by alanine, lysine, and histidine were also considered in the comparison by using the same protocol. FEP calculations allowed estimating the free energy changes from the free PKA to PKA-substrate complex (ΔΔGE→ES ) when Kemptide structure was mutated. Both ΔΔGS→ES values for homoarginine mutants were predicted with a difference below 1 kcal/mol. In addition, FEP correctly predicted that all the studied mutations decrease the catalytic efficiency of Kemptide for PKA. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Karel Mena-Ulecia
- Departamento de Ciencias Químicas, Facultad de Ciencias Exactas, Avenida República #275, Universidad Andres Bello, Santiago de Chile, Chile
| | - Fabian Gonzalez-Norambuena
- Centro de Bioinformática y Simulación Molecular, Facultad de Ingeniería, Universidad de Talca, 2 Norte 685, Casilla 721, Talca, Chile
| | - Ariela Vergara-Jaque
- Centro de Bioinformática y Simulación Molecular, Facultad de Ingeniería, Universidad de Talca, 2 Norte 685, Casilla 721, Talca, Chile
| | - Horacio Poblete
- Centro de Bioinformática y Simulación Molecular, Facultad de Ingeniería, Universidad de Talca, 2 Norte 685, Casilla 721, Talca, Chile
| | - William Tiznado
- Departamento de Ciencias Químicas, Facultad de Ciencias Exactas, Avenida República #275, Universidad Andres Bello, Santiago de Chile, Chile
| | - Julio Caballero
- Centro de Bioinformática y Simulación Molecular, Facultad de Ingeniería, Universidad de Talca, 2 Norte 685, Casilla 721, Talca, Chile
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Calixto AR, Ramos MJ, Fernandes PA. Influence of Frozen Residues on the Exploration of the PES of Enzyme Reaction Mechanisms. J Chem Theory Comput 2017; 13:5486-5495. [DOI: 10.1021/acs.jctc.7b00768] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Ana R. Calixto
- UCIBIO, REQUIMTE,
Departamento de Química
e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto, Portugal
| | - Maria J. Ramos
- UCIBIO, REQUIMTE,
Departamento de Química
e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto, Portugal
| | - Pedro A. Fernandes
- UCIBIO, REQUIMTE,
Departamento de Química
e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto, Portugal
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Metal Fluorides: Tools for Structural and Computational Analysis of Phosphoryl Transfer Enzymes. Top Curr Chem (Cham) 2017; 375:36. [PMID: 28299727 PMCID: PMC5480424 DOI: 10.1007/s41061-017-0130-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Accepted: 03/01/2017] [Indexed: 10/31/2022]
Abstract
The phosphoryl group, PO3-, is the dynamic structural unit in the biological chemistry of phosphorus. Its transfer from a donor to an acceptor atom, with oxygen much more prevalent than nitrogen, carbon, or sulfur, is at the core of a great majority of enzyme-catalyzed reactions involving phosphate esters, anhydrides, amidates, and phosphorothioates. The serendipitous discovery that the phosphoryl group could be labeled by "nuclear mutation," by substitution of PO3- by MgF3- or AlF4-, has underpinned the application of metal fluoride (MF x ) complexes to mimic transition states for enzymatic phosphoryl transfer reactions, with sufficient stability for experimental analysis. Protein crystallography in the solid state and 19F NMR in solution have enabled direct observation of ternary and quaternary protein complexes embracing MF x transition state models with precision. These studies have underpinned a radically new mechanistic approach to enzyme catalysis for a huge range of phosphoryl transfer processes, as varied as kinases, phosphatases, phosphomutases, and phosphohydrolases. The results, without exception, have endorsed trigonal bipyramidal geometry (tbp) for concerted, "in-line" stereochemistry of phosphoryl transfer. QM computations have established the validity of tbp MF x complexes as reliable models for true transition states, delivering similar bond lengths, coordination to essential metal ions, and virtually identical hydrogen bond networks. The emergence of protein control of reactant orbital overlap between bond-forming species within enzyme transition states is a new challenging theme for wider exploration.
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Pérez-Gallegos A, Garcia-Viloca M, González-Lafont À, Lluch JM. Understanding how cAMP-dependent protein kinase can catalyze phosphoryl transfer in the presence of Ca2+and Sr2+: a QM/MM study. Phys Chem Chem Phys 2017; 19:10377-10394. [DOI: 10.1039/c7cp00666g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Theoretical results demonstrate for the first time at the molecular level that the overall PKAc-catalyzed phosphoryl-transfer reaction is plausible with Ca2+and Sr2+, alkaline earth metal ions other than Mg2+, which is in good agreement with experiments.
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Affiliation(s)
- Ayax Pérez-Gallegos
- Institut de Biotecnologia i de Biomedicina and Departament de Química, Universitat Autònoma de Barcelona
- 08193 Bellaterra (Barcelona)
- Spain
| | - Mireia Garcia-Viloca
- Institut de Biotecnologia i de Biomedicina and Departament de Química, Universitat Autònoma de Barcelona
- 08193 Bellaterra (Barcelona)
- Spain
| | - Àngels González-Lafont
- Institut de Biotecnologia i de Biomedicina and Departament de Química, Universitat Autònoma de Barcelona
- 08193 Bellaterra (Barcelona)
- Spain
| | - José M. Lluch
- Institut de Biotecnologia i de Biomedicina and Departament de Química, Universitat Autònoma de Barcelona
- 08193 Bellaterra (Barcelona)
- Spain
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Gráczer É, Szimler T, Garamszegi A, Konarev PV, Lábas A, Oláh J, Palló A, Svergun DI, Merli A, Závodszky P, Weiss MS, Vas M. Dual Role of the Active Site Residues of Thermus thermophilus 3-Isopropylmalate Dehydrogenase: Chemical Catalysis and Domain Closure. Biochemistry 2016; 55:560-74. [PMID: 26731489 DOI: 10.1021/acs.biochem.5b00839] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The key active site residues K185, Y139, D217, D241, D245, and N102 of Thermus thermophilus 3-isopropylmalate dehydrogenase (Tt-IPMDH) have been replaced, one by one, with Ala. A drastic decrease in the kcat value (0.06% compared to that of the wild-type enzyme) has been observed for the K185A and D241A mutants. Similarly, the catalytic interactions (Km values) of these two mutants with the substrate IPM are weakened by more than 1 order of magnitude. The other mutants retained some (1-13%) of the catalytic activity of the wild-type enzyme and do not exhibit appreciable changes in the substrate Km values. The pH dependence of the wild-type enzyme activity (pK = 7.4) is shifted toward higher values for mutants K185A and D241A (pK values of 8.4 and 8.5, respectively). For the other mutants, smaller changes have been observed. Consequently, K185 and D241 may constitute a proton relay system that can assist in the abstraction of a proton from the OH group of IPM during catalysis. Molecular dynamics simulations provide strong support for the neutral character of K185 in the resting state of the enzyme, which implies that K185 abstracts the proton from the substrate and D241 assists the process via electrostatic interactions with K185. Quantum mechanics/molecular mechanics calculations revealed a significant increase in the activation energy of the hydride transfer of the redox step for both D217A and D241A mutants. Crystal structure analysis of the molecular contacts of the investigated residues in the enzyme-substrate complex revealed their additional importance (in particular that of K185, D217, and D241) in stabilizing the domain-closed active conformation. In accordance with this, small-angle X-ray scattering measurements indicated the complete absence of domain closure in the cases of D217A and D241A mutants, while only partial domain closure could be detected for the other mutants. This suggests that the same residues that are important for catalysis are also essential for inducing domain closure.
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Affiliation(s)
- Éva Gráczer
- Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences , Magyar tudósok krt. 2., H-1117 Budapest, Hungary
| | - Tamás Szimler
- Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences , Magyar tudósok krt. 2., H-1117 Budapest, Hungary
| | - Anita Garamszegi
- Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences , Magyar tudósok krt. 2., H-1117 Budapest, Hungary
| | - Petr V Konarev
- European Molecular Biology Laboratory , Hamburg Outstation, Notkestrasse 85, 22603 Hamburg, Germany
| | - Anikó Lábas
- Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics , Gellért tér 4., H-1111 Budapest, Hungary
| | - Julianna Oláh
- Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics , Gellért tér 4., H-1111 Budapest, Hungary
| | - Anna Palló
- Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences , Magyar tudósok krt. 2., H-1117 Budapest, Hungary
| | - Dmitri I Svergun
- European Molecular Biology Laboratory , Hamburg Outstation, Notkestrasse 85, 22603 Hamburg, Germany
| | - Angelo Merli
- Dipartimento di Bioscienze, Universitá degli Studi di Parma , Viale G.P. Usberti 23/A, I-43100 Parma, Italy
| | - Péter Závodszky
- Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences , Magyar tudósok krt. 2., H-1117 Budapest, Hungary
| | - Manfred S Weiss
- Macromolecular Crystallography (HZB-MX), Helmholtz-Zentrum Berlin für Materialien und Energie , Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
| | - Mária Vas
- Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences , Magyar tudósok krt. 2., H-1117 Budapest, Hungary
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Pérez-Gallegos A, Garcia-Viloca M, González-Lafont À, Lluch JM. SP20 Phosphorylation Reaction Catalyzed by Protein Kinase A: QM/MM Calculations Based on Recently Determined Crystallographic Structures. ACS Catal 2015. [DOI: 10.1021/acscatal.5b01064] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Ayax Pérez-Gallegos
- Institut de Biotecnologia i de Biomedicina and Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain
| | - Mireia Garcia-Viloca
- Institut de Biotecnologia i de Biomedicina and Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain
| | - Àngels González-Lafont
- Institut de Biotecnologia i de Biomedicina and Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain
| | - José M. Lluch
- Institut de Biotecnologia i de Biomedicina and Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain
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Jin HX, Go ML, Yin P, Qiu XT, Zhu P, Yan XJ. Determining the Functions of HIV-1 Tat and a Second Magnesium Ion in the CDK9/Cyclin T1 Complex: A Molecular Dynamics Simulation Study. PLoS One 2015; 10:e0124673. [PMID: 25909811 PMCID: PMC4409394 DOI: 10.1371/journal.pone.0124673] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 03/16/2015] [Indexed: 11/18/2022] Open
Abstract
The current paradigm of cyclin-dependent kinase (CDK) regulation based on the well-established CDK2 has been recently expanded. The determination of CDK9 crystal structures suggests the requirement of an additional regulatory protein, such as human immunodeficiency virus type 1 (HIV-1) Tat, to exert its physiological functions. In most kinases, the exact number and roles of the cofactor metal ions remain unappreciated, and the repertoire has thus gained increasing attention recently. Here, molecular dynamics (MD) simulations were implemented on CDK9 to explore the functional roles of HIV-1 Tat and the second Mg2+ ion at site 1 (Mg12+). The simulations unveiled that binding of HIV-1 Tat to CDK9 not only stabilized hydrogen bonds (H-bonds) between ATP and hinge residues Asp104 and Cys106, as well as between ATP and invariant Lys48, but also facilitated the salt bridge network pertaining to the phosphorylated Thr186 at the activation loop. By contrast, these H-bonds cannot be formed in CDK9 owing to the absence of HIV-1 Tat. MD simulations further revealed that the Mg12+ ion, coupled with the Mg22+ ion, anchored to the triphosphate moiety of ATP in its catalytic competent conformation. This observation indicates the requirement of the Mg12+ ion for CDK9 to realize its function. Overall, the introduction of HIV-1 Tat and Mg12+ ion resulted in the active site architectural characteristics of phosphorylated CDK9. These data highlighted the functional roles of HIV-1 Tat and Mg12+ ion in the regulation of CDK9 activity, which contributes an important complementary understanding of CDK molecular underpinnings.
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Affiliation(s)
- Hai-Xiao Jin
- Key Laboratory of Applied Marine Biotechnology Ministry of Education, School of Marine Sciences, Ningbo University, Ningbo, China
| | - Mei-Lin Go
- Department of Pharmacy, National University of Singapore, Singapore, Singapore
| | - Peng Yin
- Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education), College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha, China
| | - Xiao-Ting Qiu
- Key Laboratory of Applied Marine Biotechnology Ministry of Education, School of Marine Sciences, Ningbo University, Ningbo, China
| | - Peng Zhu
- Key Laboratory of Applied Marine Biotechnology Ministry of Education, School of Marine Sciences, Ningbo University, Ningbo, China
| | - Xiao-Jun Yan
- Key Laboratory of Applied Marine Biotechnology Ministry of Education, School of Marine Sciences, Ningbo University, Ningbo, China
- * E-mail:
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Pérez-Gallegos A, Garcia-Viloca M, González-Lafont À, Lluch JM. A QM/MM study of Kemptide phosphorylation catalyzed by protein kinase A. The role of Asp166 as a general acid/base catalyst. Phys Chem Chem Phys 2014; 17:3497-511. [PMID: 25535906 DOI: 10.1039/c4cp03579h] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In this work a theoretical study of the γ-phosphoryl group transfer from ATP to Ser17 of the synthetic substrate Kemptide (LRRASLG) in protein kinase A (PKA) has been carried out with a solvated model of the PKA-Mg2ATP-Kemptide system based on the X-ray crystallographic structure. We have used high levels (B3LYP/MM and MP2/MM) of theory to determine the overall reaction paths of the so-called concerted loose mechanism trying to clarify some aspects of that mechanism still under debate. Our calculations demonstrate for the first time in a complete model of the ternary system the viability of the final step of the catalytic mechanism in which the protonation of the phosphokemptide product by Asp166 takes place. Asp166 is a base catalyst that abstracts the HγSer17 of Kemptide thus facilitating the phosphoryl transfer, but it also acts as an acid catalyst by donating the proton just accepted from Ser17 to the O2γATP atom of the phosphoryl group.
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Affiliation(s)
- Ayax Pérez-Gallegos
- Institut de Biotecnologia i de Biomedicina and Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain.
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