1
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Pedroni L, Doherty DZ, Dall'Asta C, Galaverna G, Bell SG, Dellafiora L. Computational methods meet in vitro techniques: A case study on fusaric acid and its possible detoxification through cytochrome P450 enzymes. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2024; 273:116167. [PMID: 38447519 DOI: 10.1016/j.ecoenv.2024.116167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 02/06/2024] [Accepted: 02/27/2024] [Indexed: 03/08/2024]
Abstract
Mycotoxins are known environmental pollutants that may contaminate food and feed chains. Some mycotoxins are regulated in many countries to limit the trading of contaminated and harmful commodities. However, the so-called emerging mycotoxins are poorly understood and need to be investigated further. Fusaric acid is an emerging mycotoxin, noxious to plants and animals, but is known to be less toxic to plants when hydroxylated. The detoxification routes effective in animals have not been elucidated yet. In this context, this study integrated in silico and in vitro techniques to discover potential bioremediation routes to turn fusaric acid to its less toxic metabolites. The toxicodynamics of these forms in humans have also been addressed. An in silico screening process, followed by molecular docking and dynamics studies, identified CYP199A4 from the bacterium Rhodopseudomonas palustris HaA2 as a potential fusaric acid biotransforming enzyme. Its activity was confirmed in vitro. However, the effect of hydroxylation seemed to have a limited impact on the modelled toxicodynamics against human targets. This study represents a starting point to develop a hybrid in silico/in vitro pipeline to find bioremediation agents for other food, feed and environmental contaminants.
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Affiliation(s)
- Lorenzo Pedroni
- Department of Food and Drug, University of Parma, Parma, Italy
| | | | | | | | - Stephen G Bell
- Department of Chemistry, University of Adelaide, SA 5005, Australia.
| | - Luca Dellafiora
- Department of Food and Drug, University of Parma, Parma, Italy.
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2
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Hoffmann RJR, Gergs U, Hofmann B, Kirchhefer U, Neumann J. Temperature alters the inotropic, chronotropic and proarrhythmic effects of histamine in atrial muscle preparations from humans and H 2-receptor overexpressing mice. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2023; 396:2137-2150. [PMID: 36951998 PMCID: PMC10409711 DOI: 10.1007/s00210-023-02457-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 03/03/2023] [Indexed: 03/24/2023]
Abstract
We investigated whether hypothermia and hyperthermia can alter the efficacy and potency of histamine at increasing the force of cardiac contractions in mice that overexpress the human H2 receptor only in their cardiac myocytes (labelled H2-TG). Contractile studies were performed in an organ bath on isolated, electrically driven (1 Hz) left atrial preparations and spontaneously beating right atrial preparations from H2-TG mice and wild-type (WT) littermate control mice. The basal beating rate in the right atrial preparations from H2-TG mice was lowered by hypothermia (23 °C) and elevated by hyperthermia (42 °C). Furthermore, the efficacy of histamine (0.01-100 µM) at exerting positive inotropic effects was more severely attenuated in the left and right H2-TG mouse atria under hypothermia and hyperthermia than under normothermia (37 °C). Similarly, the inotropic response to histamine was attenuated under hypothermia and hyperthermia in isolated electrically stimulated (1 Hz) right atrial preparations obtained from humans undergoing cardiac surgery. The phosphorylation state of phospholamban at serine 16 at 23 °C was inferior to that at 37 °C in left atrial preparations from H2-TG mice in the presence of 10 µM histamine. In contrast, in human atrial preparations, the phosphorylation state of phospholamban at serine 16 in the presence of 100 µM histamine was lower at 42 °C than at 37 °C. Finally, under hyperthermia, we recorded more and longer lasting arrhythmias in right atrial preparations from H2-TG mice than in those from WT mice. We conclude that the inotropic effects of histamine in H2-TG mice and in human atrial preparations, as well as the chronotropic effects of histamine in H2-TG mice, are temperature dependent. Furthermore, we observed that, even without stimulation of the H2 receptors by exogenous agonists, temperature elevation can increase arrhythmias in isolated right atrial preparations from H2-TG mice. We propose that H2 receptors play a role in hyperthermia-induced supraventricular arrhythmias in human patients.
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Affiliation(s)
- Robert J. R. Hoffmann
- Institut Für Pharmakologie und Toxikologie, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, 06097 Halle, Germany
| | - Ulrich Gergs
- Institut Für Pharmakologie und Toxikologie, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, 06097 Halle, Germany
| | - Britt Hofmann
- Medizinische Fakultät, Herzchirurgie, Martin-Luther-Universität Halle-Wittenberg, 06097 Halle, Germany
| | - Uwe Kirchhefer
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Westfälische Wilhelms-Universität, Domagkstr. 12, 48149 Münster, Germany
| | - Joachim Neumann
- Institut Für Pharmakologie und Toxikologie, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, 06097 Halle, Germany
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3
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Qin J, Zhang J, Lin L, Haji-Ghassemi O, Lin Z, Woycechowsky KJ, Van Petegem F, Zhang Y, Yuchi Z. Structures of PKA-phospholamban complexes reveal a mechanism of familial dilated cardiomyopathy. eLife 2022; 11:75346. [PMID: 35297759 PMCID: PMC8970585 DOI: 10.7554/elife.75346] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 03/16/2022] [Indexed: 01/07/2023] Open
Abstract
Several mutations identified in phospholamban (PLN) have been linked to familial dilated cardiomyopathy (DCM) and heart failure, yet the underlying molecular mechanism remains controversial. PLN interacts with sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) and regulates calcium uptake, which is modulated by the protein kinase A (PKA)-dependent phosphorylation of PLN during the fight-or-flight response. Here, we present the crystal structures of the catalytic domain of mouse PKA in complex with wild-type and DCM-mutant PLNs. Our structures, combined with the results from other biophysical and biochemical assays, reveal a common disease mechanism: the mutations in PLN reduce its phosphorylation level by changing its conformation and weakening its interactions with PKA. In addition, we demonstrate that another more ubiquitous SERCA-regulatory peptide, called another-regulin (ALN), shares a similar mechanism mediated by PKA in regulating SERCA activity.
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Affiliation(s)
- Juan Qin
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency; Collaborative Innovation Center of Chemical Science and Engineering; School of Pharmaceutical Science and Technology, Tianjin UniversityTianjinChina
| | - Jingfeng Zhang
- Wuhan Institute of Physics and Mathematics, Chinese Academy of SciencesWuhanChina
| | - Lianyun Lin
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency; Collaborative Innovation Center of Chemical Science and Engineering; School of Pharmaceutical Science and Technology, Tianjin UniversityTianjinChina
| | - Omid Haji-Ghassemi
- Department of Biochemistry and Molecular Biology, The Life Sciences Centre, University of British ColumbiaVancouverCanada
| | - Zhi Lin
- School of Life Sciences, Tianjin UniversityTianjinChina
| | - Kenneth J Woycechowsky
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency; Collaborative Innovation Center of Chemical Science and Engineering; School of Pharmaceutical Science and Technology, Tianjin UniversityTianjinChina
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, The Life Sciences Centre, University of British ColumbiaVancouverCanada
| | - Yan Zhang
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency; Collaborative Innovation Center of Chemical Science and Engineering; School of Pharmaceutical Science and Technology, Tianjin UniversityTianjinChina
| | - Zhiguang Yuchi
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency; Collaborative Innovation Center of Chemical Science and Engineering; School of Pharmaceutical Science and Technology, Tianjin UniversityTianjinChina,Department of Molecular Pharmacology, Tianjin Medical University Cancer Institute & Hospital; National Clinical Research Center for Cancer; Key Laboratory of Cancer Prevention and Therapy, Tianjin; Tianjin’s Clinical Research Center for CancerTianjinChina
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4
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A target fishing study to spot possible biological targets of fusaric acid: Inhibition of protein kinase-A and insights on the underpinning mechanisms. Food Chem Toxicol 2021; 159:112663. [PMID: 34748883 DOI: 10.1016/j.fct.2021.112663] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 10/27/2021] [Accepted: 11/03/2021] [Indexed: 12/23/2022]
Abstract
Fusaric acid is a secondary metabolite produced by various Fusarium fungi, present with relatively high incidence in Fusarium-contaminated foods. It was already described as phytotoxic and cytotoxic. However, the understanding of its molecular mechanisms is still fragmentary and further data are needed to ensure an informed assessment of the risk related to its presence in food. This work applied an integrated in silico/in vitro approach to reveal novel potential biological activities of fusaric acid and to investigate the underpinning mechanisms. An in silico reverse screening was used to identify novel biological targets for fusaric acid. Computational results indicated as target protein kinase-A, which was confirmed with biochemical cell-free assays providing evidence of its actual inhibitory potential. Cell-based experiments on intestinal cells (HCEC-1CT cells) identified the mitochondrial network and cell membranes as potentially affected organelles, possibly resulting from PKA inhibition. The integration of 3D molecular modeling supported the plausibility of fusaric acid-dependent inhibition. From the hazard identification perspective, considering the Low Observed Adverse Effect Level described here (0.1 mM) and the possible level of contamination in food, fusaric acid might raise concern from a food safety standpoint and the gastrointestinal tract was described as a meaningful system to investigate with priority.
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Kumar K, Wang P, Wilson J, Zlatanic V, Berrouet C, Khamrui S, Secor C, Swartz EA, Lazarus MB, Sanchez R, Stewart AF, Garcia-Ocana A, DeVita RJ. Synthesis and Biological Validation of a Harmine-Based, Central Nervous System (CNS)-Avoidant, Selective, Human β-Cell Regenerative Dual-Specificity Tyrosine Phosphorylation-Regulated Kinase A (DYRK1A) Inhibitor. J Med Chem 2020; 63:2986-3003. [PMID: 32003560 PMCID: PMC7388697 DOI: 10.1021/acs.jmedchem.9b01379] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Recently, our group identified that harmine is able to induce β-cell proliferation both in vitro and in vivo, mediated via the DYRK1A-NFAT pathway. Since, harmine suffers from a lack of selectivity, both against other kinases and CNS off-targets, we therefore sought to expand structure-activity relationships for harmine's DYRK1A activity, to enhance selectivity for off-targets while retaining human β-cell proliferation activity. We carried out optimization of the 9-N-position of harmine to synthesize 29 harmine-based analogs. Several novel inhibitors showed excellent DYRK1A inhibition and human β-cell proliferation capability. An optimized DYRK1A inhibitor, 2-2c, was identified as a novel, efficacious in vivo lead candidate. 2-2c also demonstrates improved selectivity for kinases and CNS off-targets, as well as in vivo efficacy for β-cell proliferation and regeneration at lower doses than harmine. Collectively, these findings demonstrate that 2-2c is a much improved in vivo lead candidate as compared to harmine for the treatment of diabetes.
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Affiliation(s)
- Kunal Kumar
- Drug Discovery Institute, Icahn School of Medicine at Mount
Sinai, New York, NY 10029, USA
- Department of Pharmacological Sciences, Icahn School of
Medicine at Mount Sinai, New York, NY 10029, USA
| | - Peng Wang
- Diabetes, Obesity, and Metabolism Institute, Icahn School
of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Jessica Wilson
- Diabetes, Obesity, and Metabolism Institute, Icahn School
of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Viktor Zlatanic
- Diabetes, Obesity, and Metabolism Institute, Icahn School
of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Cecilia Berrouet
- Diabetes, Obesity, and Metabolism Institute, Icahn School
of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Susmita Khamrui
- Department of Pharmacological Sciences, Icahn School of
Medicine at Mount Sinai, New York, NY 10029, USA
| | - Cody Secor
- Department of Pharmacological Sciences, Icahn School of
Medicine at Mount Sinai, New York, NY 10029, USA
| | - Ethan A. Swartz
- Diabetes, Obesity, and Metabolism Institute, Icahn School
of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Michael B. Lazarus
- Drug Discovery Institute, Icahn School of Medicine at Mount
Sinai, New York, NY 10029, USA
- Department of Pharmacological Sciences, Icahn School of
Medicine at Mount Sinai, New York, NY 10029, USA
| | - Roberto Sanchez
- Drug Discovery Institute, Icahn School of Medicine at Mount
Sinai, New York, NY 10029, USA
- Department of Pharmacological Sciences, Icahn School of
Medicine at Mount Sinai, New York, NY 10029, USA
| | - Andrew F. Stewart
- Diabetes, Obesity, and Metabolism Institute, Icahn School
of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Adolfo Garcia-Ocana
- Diabetes, Obesity, and Metabolism Institute, Icahn School
of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Robert J. DeVita
- Drug Discovery Institute, Icahn School of Medicine at Mount
Sinai, New York, NY 10029, USA
- Department of Pharmacological Sciences, Icahn School of
Medicine at Mount Sinai, New York, NY 10029, USA
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6
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Molecular Fingerprints for a Novel Enzyme Family in Actinobacteria with Glucosamine Kinase Activity. mBio 2019; 10:mBio.00239-19. [PMID: 31088917 PMCID: PMC6520443 DOI: 10.1128/mbio.00239-19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The discovery of novel enzymes involved in antibiotic biosynthesis pathways is currently a topic of utmost importance. The high levels of antibiotic resistance detected worldwide threaten our ability to combat infections and other 20th-century medical achievements, namely, organ transplantation or cancer chemotherapy. We have identified and characterized a unique family of enzymes capable of phosphorylating glucosamine to glucosamine-6-phosphate, a crucial molecule directly involved in the activation of antibiotic production pathways in Actinobacteria, nature’s main source of antimicrobials. The consensus sequence identified for these glucosamine kinases will help establish a molecular fingerprint to reveal yet-uncharacterized sequences in antibiotic producers, which should have an important impact in biotechnological and biomedical applications, including the enhancement and optimization of antibiotic production. Actinobacteria have long been the main source of antibiotics, secondary metabolites with tightly controlled biosynthesis by environmental and physiological factors. Phosphorylation of exogenous glucosamine has been suggested as a mechanism for incorporation of this extracellular material into secondary metabolite biosynthesis, but experimental evidence of specific glucosamine kinases in Actinobacteria is lacking. Here, we present the molecular fingerprints for the identification of a unique family of actinobacterial glucosamine kinases. Structural and biochemical studies on a distinctive kinase from the soil bacterium Streptacidiphilus jiangxiensis unveiled its preference for glucosamine and provided structural evidence of a phosphoryl transfer to this substrate. Conservation of glucosamine-contacting residues across a large number of uncharacterized actinobacterial proteins unveiled a specific glucosamine binding sequence motif. This family of kinases and their genetic context may represent the missing link for the incorporation of environmental glucosamine into the antibiotic biosynthesis pathways in Actinobacteria and can be explored to enhance antibiotic production.
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7
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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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8
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Wei Q, Yang S, Li D, Zhang X, Zheng J, Jia Z. A new autoinhibited kinase conformation reveals a salt-bridge switch in kinase activation. Sci Rep 2016; 6:28437. [PMID: 27324091 PMCID: PMC4914941 DOI: 10.1038/srep28437] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 06/06/2016] [Indexed: 11/09/2022] Open
Abstract
In the structure of autoinhibited EphA2 tyrosine kinase reported herein, we have captured the entire activation segment, revealing a previously unknown role of the conserved Arg762 in kinase autoinhibition by interacting with the essential Mg2+-chelating Asp757. While it is well known that this Arg residue is involved in an electrostatic interaction with the phospho-residue of the activation loop to stabilize the active conformation, our structure determination revealed a new role for the Arg, acting as a switch between the autoinhibited and activated conformations. Mutation of Arg762 to Ala in EphA2 sensitized Mg2+ response, resulting in enhanced kinase catalytic activity and Mg2+ cooperativity. Furthermore, mutation of the corresponding Arg/Lys to Ala in PKA and p38MAPK also exhibited similar behavior. This new salt bridge-mediated switch may thus be an important mechanism of activation on a broader scope for kinases which utilize autophosphorylation.
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Affiliation(s)
- Qiang Wei
- College of Chemistry, Beijing Normal University, Beijing, 100875, China
| | - Shaoyuan Yang
- College of Chemistry, Beijing Normal University, Beijing, 100875, China
| | - Dan Li
- College of Chemistry, Beijing Normal University, Beijing, 100875, China
| | - Xiaoying Zhang
- College of Chemistry, Beijing Normal University, Beijing, 100875, China
| | - Jimin Zheng
- College of Chemistry, Beijing Normal University, Beijing, 100875, China
| | - Zongchao Jia
- College of Chemistry, Beijing Normal University, Beijing, 100875, China.,Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, K7L 3N6, Canada
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9
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Sensitive array-based assay for determination of serological protein kinase A autoantibody levels based on its antigen protein activation. Clin Biochem 2016; 49:127-31. [DOI: 10.1016/j.clinbiochem.2015.08.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 08/21/2015] [Accepted: 08/25/2015] [Indexed: 11/18/2022]
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10
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Das A, Gerlits O, Parks JM, Langan P, Kovalevsky A, Heller WT. Protein Kinase A Catalytic Subunit Primed for Action: Time-Lapse Crystallography of Michaelis Complex Formation. Structure 2015; 23:2331-2340. [PMID: 26585512 DOI: 10.1016/j.str.2015.10.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 08/31/2015] [Accepted: 10/01/2015] [Indexed: 10/22/2022]
Abstract
The catalytic subunit of the cyclic AMP-dependent protein kinase A (PKAc) catalyzes the transfer of the γ-phosphate of bound Mg2ATP to a serine or threonine residue of a protein substrate. Here, time-lapse X-ray crystallography was used to capture a series of complexes of PKAc with an oligopeptide substrate and unreacted Mg2ATP, including the Michaelis complex, that reveal important geometric rearrangements in and near the active site preceding the phosphoryl transfer reaction. Contrary to the prevailing view, Mg(2+) binds first to the M1 site as a complex with ATP and is followed by Mg(2+) binding to the M2 site. Concurrently, the target serine hydroxyl of the peptide substrate rotates away from the active site toward the bulk solvent, which breaks the hydrogen bond with D166. Lastly, the serine hydroxyl of the substrate rotates back toward D166 to form the Michaelis complex with the active site primed for phosphoryl transfer.
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Affiliation(s)
- Amit Das
- Biology & Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
| | - Oksana Gerlits
- Biology & Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Jerry M Parks
- UT/ORNL Center for Molecular Biophysics, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Paul Langan
- Biology & Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Andrey Kovalevsky
- Biology & Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - William T Heller
- Biology & Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
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11
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Knape MJ, Ahuja LG, Bertinetti D, Burghardt NC, Zimmermann B, Taylor SS, Herberg FW. Divalent Metal Ions Mg²⁺ and Ca²⁺ Have Distinct Effects on Protein Kinase A Activity and Regulation. ACS Chem Biol 2015. [PMID: 26200257 DOI: 10.1021/acschembio.5b00271] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
cAMP-dependent protein kinase (PKA) is regulated primarily in response to physiological signals while nucleotides and metals may provide fine-tuning. PKA can use different metal ions for phosphoryl transfer, yet some, like Ca(2+), do not support steady-state catalysis. Fluorescence Polarization (FP) and Surface Plasmon Resonance (SPR) were used to study inhibitor and substrate interactions with PKA. The data illustrate how metals can act differentially as a result of their inherent coordination properties. We found that Ca(2+), in contrast to Mg(2+), does not induce high-affinity binding of PKA to pseudosubstrate inhibitors. However, Ca(2+) works in a single turnover mode to allow for phosphoryl-transfer. Using a novel SPR approach, we were able to directly monitor the interaction of PKA with a substrate in the presence of Mg(2+)ATP. This allows us to depict the entire kinase reaction including complex formation as well as release of the phosphorylated substrate. In contrast to Mg(2+), Ca(2+) apparently slows down the enzymatic reaction. A focus on individual reaction steps revealed that Ca(2+) is not as efficient as Mg(2+) in stabilizing the enzyme:substrate complex. The opposite holds true for product dissociation where Mg(2+) easily releases the phospho-substrate while Ca(2+) traps both reaction products at the active site. This explains the low steady-state activity in the presence of Ca(2+). Furthermore, Ca(2+) is able to modulate kinase activity as well as inhibitor binding even in the presence of Mg(2+). We therefore hypothesize that the physiological metal ions Mg(2+) and Ca(2+) both play a role in kinase activity and regulation. Since PKA is localized close to calcium channels and may render PKA activity susceptible to Ca(2+), our data provide a possible mechanism for novel crosstalk between cAMP and calcium signaling.
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Affiliation(s)
- Matthias J. Knape
- Department
of Biochemistry, University of Kassel, 34132 Kassel, Germany
| | - Lalima G. Ahuja
- Department
of Pharmacology, University of California at San Diego, La Jolla, California 92093, United States
| | | | | | | | - Susan S. Taylor
- Department
of Pharmacology, University of California at San Diego, La Jolla, California 92093, United States
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12
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Di Michele M, Stes E, Vandermarliere E, Arora R, Astorga-Wells J, Vandenbussche J, van Heerde E, Zubarev R, Bonnet P, Linders JTM, Jacoby E, Brehmer D, Martens L, Gevaert K. Limited Proteolysis Combined with Stable Isotope Labeling Reveals Conformational Changes in Protein (Pseudo)kinases upon Binding Small Molecules. J Proteome Res 2015; 14:4179-93. [PMID: 26293246 DOI: 10.1021/acs.jproteome.5b00282] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Likely due to conformational rearrangements, small molecule inhibitors may stabilize the active conformation of protein kinases and paradoxically promote tumorigenesis. We combined limited proteolysis with stable isotope labeling MS to monitor protein conformational changes upon binding of small molecules. Applying this method to the human serine/threonine kinase B-Raf, frequently mutated in cancer, we found that binding of ATP or its nonhydrolyzable analogue AMP-PNP, but not ADP, stabilized the structure of both B-Raf(WT) and B-Raf(V600E). The ATP-competitive type I B-Raf inhibitor vemurafenib and the type II inhibitor sorafenib stabilized the kinase domain (KD) but had distinct effects on the Ras-binding domain. Stabilization of the B-Raf(WT) KD was confirmed by hydrogen/deuterium exchange MS and molecular dynamics simulations. Our results are further supported by cellular assays in which we assessed cell viability and phosphorylation profiles in cells expressing B-Raf(WT) or B-Raf(V600E) in response to vemurafenib or sorafenib. Our data indicate that an overall stabilization of the B-Raf structure by specific inhibitors activates MAPK signaling and increases cell survival, helping to explain clinical treatment failure. We also applied our method to monitor conformational changes upon nucleotide binding of the pseudokinase KSR1, which holds high potential for inhibition in human diseases.
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Affiliation(s)
- Michela Di Michele
- Department of Medical Protein Research, VIB , A. Baertsoenkaai 3, 9000 Ghent, Belgium.,Department of Biochemistry, Ghent University , A. Baertsoenkaai 3, 9000 Ghent, Belgium
| | - Elisabeth Stes
- Department of Medical Protein Research, VIB , A. Baertsoenkaai 3, 9000 Ghent, Belgium.,Department of Biochemistry, Ghent University , A. Baertsoenkaai 3, 9000 Ghent, Belgium
| | - Elien Vandermarliere
- Department of Medical Protein Research, VIB , A. Baertsoenkaai 3, 9000 Ghent, Belgium.,Department of Biochemistry, Ghent University , A. Baertsoenkaai 3, 9000 Ghent, Belgium
| | - Rohit Arora
- Institut de Chimie Organique et Analytique (ICOA), UMR 7311 CNRS-Université d'Orléans , Pôle de chimie, Rue de Chartres, 45100 Orléans, France
| | | | - Jonathan Vandenbussche
- Department of Medical Protein Research, VIB , A. Baertsoenkaai 3, 9000 Ghent, Belgium.,Department of Biochemistry, Ghent University , A. Baertsoenkaai 3, 9000 Ghent, Belgium
| | - Erika van Heerde
- Oncology Discovery, Janssen Research and Development, A Division of Janssen Pharmaceutica NV , Turnhoutseweg 30, B-2340 Beerse, Belgium
| | - Roman Zubarev
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet , Scheelelaberatoriet Scheeles väg 2, SE-171 77 Stockholm, Sweden
| | - Pascal Bonnet
- Institut de Chimie Organique et Analytique (ICOA), UMR 7311 CNRS-Université d'Orléans , Pôle de chimie, Rue de Chartres, 45100 Orléans, France
| | - Joannes T M Linders
- Oncology Discovery, Janssen Research and Development, A Division of Janssen Pharmaceutica NV , Turnhoutseweg 30, B-2340 Beerse, Belgium
| | - Edgar Jacoby
- Oncology Discovery, Janssen Research and Development, A Division of Janssen Pharmaceutica NV , Turnhoutseweg 30, B-2340 Beerse, Belgium
| | - Dirk Brehmer
- Oncology Discovery, Janssen Research and Development, A Division of Janssen Pharmaceutica NV , Turnhoutseweg 30, B-2340 Beerse, Belgium
| | - Lennart Martens
- Department of Medical Protein Research, VIB , A. Baertsoenkaai 3, 9000 Ghent, Belgium.,Department of Biochemistry, Ghent University , A. Baertsoenkaai 3, 9000 Ghent, Belgium
| | - Kris Gevaert
- Department of Medical Protein Research, VIB , A. Baertsoenkaai 3, 9000 Ghent, Belgium.,Department of Biochemistry, Ghent University , A. Baertsoenkaai 3, 9000 Ghent, Belgium
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13
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Fouda AE, Pflum MKH. A Cell-Permeable ATP Analogue for Kinase-Catalyzed Biotinylation. Angew Chem Int Ed Engl 2015; 54:9618-21. [PMID: 26119262 PMCID: PMC4551444 DOI: 10.1002/anie.201503041] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 05/07/2015] [Indexed: 01/20/2023]
Abstract
ATP analogues have been powerful compounds for the study of kinase-catalyzed phosphorylation. However, the cell impermeability of ATP analogues has largely limited their use to in vitro lysate-based experiments. Herein, we report the first cell-permeable ATP analogue, ATP-polyamine-biotin (APB). APB is shown to promote biotin labeling of kinase substrates in live cells and has future applications in phosphoprotein purification and analysis. More generally, these studies provide a foundation for the development of additional cell-permeable ATP analogues for cell-signaling research.
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Affiliation(s)
- Ahmed E Fouda
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, MI 48202 (USA) http://chem.wayne.edu/pflumgroup/
| | - Mary Kay H Pflum
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, MI 48202 (USA) http://chem.wayne.edu/pflumgroup/.
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14
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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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15
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Fouda AE, Pflum MKH. A Cell-Permeable ATP Analogue for Kinase-Catalyzed Biotinylation. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201503041] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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16
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Gerlits O, Tian J, Das A, Langan P, Heller WT, Kovalevsky A. Phosphoryl Transfer Reaction Snapshots in Crystals: INSIGHTS INTO THE MECHANISM OF PROTEIN KINASE A CATALYTIC SUBUNIT. J Biol Chem 2015; 290:15538-15548. [PMID: 25925954 DOI: 10.1074/jbc.m115.643213] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Indexed: 11/06/2022] Open
Abstract
To study the catalytic mechanism of phosphorylation catalyzed by cAMP-dependent protein kinase (PKA) a structure of the enzyme-substrate complex representing the Michaelis complex is of specific interest as it can shed light on the structure of the transition state. However, all previous crystal structures of the Michaelis complex mimics of the PKA catalytic subunit (PKAc) were obtained with either peptide inhibitors or ATP analogs. Here we utilized Ca(2+) ions and sulfur in place of the nucleophilic oxygen in a 20-residue pseudo-substrate peptide (CP20) and ATP to produce a close mimic of the Michaelis complex. In the ternary reactant complex, the thiol group of Cys-21 of the peptide is facing Asp-166 and the sulfur atom is positioned for an in-line phosphoryl transfer. Replacement of Ca(2+) cations with Mg(2+) ions resulted in a complex with trapped products of ATP hydrolysis: phosphate ion and ADP. The present structural results in combination with the previously reported structures of the transition state mimic and phosphorylated product complexes complete the snapshots of the phosphoryl transfer reaction by PKAc, providing us with the most thorough picture of the catalytic mechanism to date.
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Affiliation(s)
- Oksana Gerlits
- From the Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
| | - Jianhui Tian
- From the Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
| | - Amit Das
- From the Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
| | - Paul Langan
- From the Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
| | - William T Heller
- From the Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831.
| | - Andrey Kovalevsky
- From the Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831.
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17
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Kong DH, Jung SH, Jeon HY, Kim WJ, Kim YM, Ha KS. A peptide array-based serological protein kinase A activity assay and its application in cancer diagnosis. Analyst 2015; 140:6588-6594. [DOI: 10.1039/c5an01151e] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023]
Abstract
Protein kinase A (PKA) plays a crucial role in several biological processes; however, there is no assay with sufficient sensitivity and specificity to determine serological PKA (sPKA) activity.
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Affiliation(s)
- Deok-Hoon Kong
- Department of Molecular and Cellular Biochemistry and Institute of Medical Science
- Kangwon National University School of Medicine
- Chuncheon
- Korea
| | - Se-Hui Jung
- Department of Molecular and Cellular Biochemistry and Institute of Medical Science
- Kangwon National University School of Medicine
- Chuncheon
- Korea
| | - Hye-Yoon Jeon
- Department of Molecular and Cellular Biochemistry and Institute of Medical Science
- Kangwon National University School of Medicine
- Chuncheon
- Korea
| | - Woo-Jin Kim
- Department of Internal Medicine
- Kangwon National University School of Medicine
- Chuncheon
- Korea
| | - Young-Myeong Kim
- Department of Molecular and Cellular Biochemistry and Institute of Medical Science
- Kangwon National University School of Medicine
- Chuncheon
- Korea
| | - Kwon-Soo Ha
- Department of Molecular and Cellular Biochemistry and Institute of Medical Science
- Kangwon National University School of Medicine
- Chuncheon
- Korea
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18
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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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19
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Abstract
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Although ADP release is the rate
limiting step in product turnover
by protein kinase A, the steps and motions involved in this process
are not well resolved. Here we report the apo and ADP bound structures
of the myristylated catalytic subunit of PKA at 2.9 and 3.5 Å
resolution, respectively. The ADP bound structure adopts a conformation
that does not conform to the previously characterized open, closed,
or intermediate states. In the ADP bound structure, the C-terminal
tail and Gly-rich loop are more closed than in the open state adopted
in the apo structure but are also much more open than the intermediate
or closed conformations. Furthermore, ADP binds at the active site
with only one magnesium ion, termed Mg2 from previous structures.
These structures thus support a model where ADP release proceeds through
release of the substrate and Mg1 followed by lifting of the Gly-rich
loop and disengagement of the C-terminal tail. Coupling of these two
structural elements with the release of the first metal ion fills
in a key step in the catalytic cycle that has been missing and supports
an ensemble of correlated conformational states that mediate the full
catalytic cycle for a protein kinase.
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Affiliation(s)
- Adam C Bastidas
- Department of Pharmacology, University of California, San Diego , San Diego, California 92093, United States
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20
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Gerlits O, Das A, Keshwani MM, Taylor S, Waltman MJ, Langan P, Heller WT, Kovalevsky A. Metal-free cAMP-dependent protein kinase can catalyze phosphoryl transfer. Biochemistry 2014; 53:3179-86. [PMID: 24786636 PMCID: PMC4030786 DOI: 10.1021/bi5000965] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
X-ray structures of several ternary product complexes of the catalytic subunit of cAMP-dependent protein kinase (PKAc) have been determined with no bound metal ions and with Na(+) or K(+) coordinated at two metal-binding sites. The metal-free PKAc and the enzyme with alkali metals were able to facilitate the phosphoryl transfer reaction. In all studied complexes, the ATP and the substrate peptide (SP20) were modified into the products ADP and the phosphorylated peptide. The products of the phosphotransfer reaction were also found when ATP-γS, a nonhydrolyzable ATP analogue, reacted with SP20 in the PKAc active site containing no metals. Single turnover enzyme kinetics measurements utilizing (32)P-labeled ATP confirmed the phosphotransferase activity of the enzyme in the absence of metal ions and in the presence of alkali metals. In addition, the structure of the apo-PKAc binary complex with SP20 suggests that the sequence of binding events may become ordered in a metal-free environment, with SP20 binding first to prime the enzyme for subsequent ATP binding. Comparison of these structures reveals conformational and hydrogen bonding changes that might be important for the mechanism of catalysis.
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Affiliation(s)
- Oksana Gerlits
- Biology and Soft Matter Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
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21
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Gerlits O, Waltman MJ, Taylor S, Langan P, Kovalevsky A. Insights into the phosphoryl transfer catalyzed by cAMP-dependent protein kinase: an X-ray crystallographic study of complexes with various metals and peptide substrate SP20. Biochemistry 2013; 52:3721-7. [PMID: 23672593 PMCID: PMC3666212 DOI: 10.1021/bi400066a] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
X-ray
structures of several ternary substrate and product complexes
of the catalytic subunit of cAMP-dependent protein kinase (PKAc) have
been determined with different bound metal ions. In the PKAc complexes,
Mg2+, Ca2+, Sr2+, and Ba2+ metal ions could bind to the active site and facilitate the phosphoryl
transfer reaction. ATP and a substrate peptide (SP20) were modified,
and the reaction products ADP and the phosphorylated peptide were
found trapped in the enzyme active site. Finally, we determined the
structure of a pseudo-Michaelis complex containing Mg2+, nonhydrolyzable AMP-PCP (β,γ-methyleneadenosine 5′-triphosphate)
and SP20. The product structures together with the pseudo-Michaelis
complex provide snapshots of different stages of the phosphorylation
reaction. Comparison of these structures reveals conformational, coordination,
and hydrogen bonding changes that might occur during the reaction
and shed new light on its mechanism, roles of metals, and active site
residues.
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Affiliation(s)
- Oksana Gerlits
- Bioscience Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87544, United States
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22
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Bastidas AC, Deal MS, Steichen JM, Guo Y, Wu J, Taylor SS. Phosphoryl transfer by protein kinase A is captured in a crystal lattice. J Am Chem Soc 2013; 135:4788-98. [PMID: 23458248 PMCID: PMC3663052 DOI: 10.1021/ja312237q] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The catalytic (C) subunit of cAMP-dependent protein kinase (PKA) is a serine/threonine kinase responsible for most of the effects of cAMP signaling, and PKA serves as a prototype for the entire kinase family. Despite multiple studies of PKA, the steps involved in phosphoryl transfer, the roles of the catalytically essential magnesium ions, and the processes that govern the rate-limiting step of ADP release are unresolved. Here we identified conditions that yielded slow phosphoryl transfer of the γ-phosphate from the generally nonhydrolyzable analog of ATP, adenosine-5'-(β,γ-imido)triphosphate (AMP-PNP), onto a substrate peptide within protein crystals. By trapping both products in the crystal lattice, we now have a complete resolution profile of all the catalytic steps. One crystal structure refined to 1.55 Å resolution shows two states of the protein with 55% displaying intact AMP-PNP and an unphosphorylated substrate and 45% displaying transfer of the γ-phosphate of AMP-PNP onto the substrate peptide yielding AMP-PN and a phosphorylated substrate. Another structure refined to 2.15 Å resolution displays complete phosphoryl transfer to the substrate. These structures, in addition to trapping both products in the crystal lattice, implicate one magnesium ion, previously termed Mg2, as the more stably bound ion. Following phosphoryl transfer, Mg2 recruits a water molecule to retain an octahedral coordination geometry suggesting the strong binding character of this magnesium ion, and Mg2 remains in the active site following complete phosphoryl transfer while Mg1 is expelled. Loss of Mg1 may thus be an important part of the rate-limiting step of ADP release.
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Affiliation(s)
- Adam C. Bastidas
- Department of Pharmacology; University of California, San Diego, CA 92093, USA
| | - Michael S. Deal
- Department of Chemistry and Biochemistry; University of California, San Diego, CA 92093, USA
| | - Jon M. Steichen
- Department of Chemistry and Biochemistry; University of California, San Diego, CA 92093, USA
| | - Yurong Guo
- Department of Chemistry and Biochemistry; University of California, San Diego, CA 92093, USA
| | - Jian Wu
- Department of Chemistry and Biochemistry; University of California, San Diego, CA 92093, USA
| | - Susan S. Taylor
- Department of Pharmacology; University of California, San Diego, CA 92093, USA
- Department of Chemistry and Biochemistry; University of California, San Diego, CA 92093, USA
- Howard Hughes Medical Institute; University of California, San Diego, CA 92093, USA
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23
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Grädler U, Schwarz D, Dresing V, Musil D, Bomke J, Frech M, Greiner H, Jäkel S, Rysiok T, Müller-Pompalla D, Wegener A. Structural and biophysical characterization of the Syk activation switch. J Mol Biol 2012; 425:309-33. [PMID: 23154170 DOI: 10.1016/j.jmb.2012.11.007] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 11/05/2012] [Accepted: 11/06/2012] [Indexed: 11/28/2022]
Abstract
Syk is an essential non-receptor tyrosine kinase in intracellular immunological signaling, and the control of Syk kinase function is considered as a valuable target for pharmacological intervention in autoimmune or inflammation diseases. Upon immune receptor stimulation, the kinase activity of Syk is regulated by binding of phosphorylated immune receptor tyrosine-based activating motifs (pITAMs) to the N-terminal tandem Src homology 2 (tSH2) domain and by autophosphorylation with consequences for the molecular structure of the Syk protein. Here, we present the first crystal structures of full-length Syk (fl-Syk) as wild type and as Y348F,Y352F mutant forms in complex with AMP-PNP revealing an autoinhibited conformation. The comparison with the crystal structure of the truncated Syk kinase domain in complex with AMP-PNP taken together with ligand binding studies by surface plasmon resonance (SPR) suggests conformational differences in the ATP sites of autoinhibited and activated Syk forms. This hypothesis was corroborated by studying the thermodynamic and kinetic interaction of three published Syk inhibitors with isothermal titration calorimetry and SPR, respectively. We further demonstrate the modulation of inhibitor binding affinities in the presence of pITAM and discuss the observed differences of thermodynamic and kinetic signatures. The functional relevance of pITAM binding to fl-Syk was confirmed by a strong stimulation of in vitro autophosphorylation. A structural feedback mechanism on the kinase domain upon pITAM binding to the tSH2 domain is discussed in analogy of the related family kinase ZAP-70 (Zeta-chain-associated protein kinase 70). Surprisingly, we observed distinct conformations of the tSH2 domain and the activation switch including Tyr348 and Tyr352 in the interdomain linker of Syk in comparison to ZAP-70.
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Affiliation(s)
- Ulrich Grädler
- Merck KGaA, Merck Serono Research, Small Molecule Platform/MIB, Frankfurter Str. 250, 64293 Darmstadt, Germany.
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