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Schloßhauer JL, Dondapati SK, Kubick S, Zemella A. A Cost-Effective Pichia pastoris Cell-Free System Driven by Glycolytic Intermediates Enables the Production of Complex Eukaryotic Proteins. Bioengineering (Basel) 2024; 11:92. [PMID: 38247969 PMCID: PMC10813726 DOI: 10.3390/bioengineering11010092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 01/12/2024] [Accepted: 01/15/2024] [Indexed: 01/23/2024] Open
Abstract
Cell-free systems are particularly attractive for screening applications and the production of difficult-to-express proteins. However, the production of cell lysates is difficult to implement on a larger scale due to large time requirements, cultivation costs, and the supplementation of cell-free reactions with energy regeneration systems. Consequently, the methylotrophic yeast Pichia pastoris, which is widely used in recombinant protein production, was utilized in the present study to realize cell-free synthesis in a cost-effective manner. Sensitive disruption conditions were evaluated, and appropriate signal sequences for translocation into ER vesicles were identified. An alternative energy regeneration system based on fructose-1,6-bisphosphate was developed and a ~2-fold increase in protein production was observed. Using a statistical experiment design, the optimal composition of the cell-free reaction milieu was determined. Moreover, functional ion channels could be produced, and a G-protein-coupled receptor was site-specifically modified using the novel cell-free system. Finally, the established P. pastoris cell-free protein production system can economically produce complex proteins for biotechnological applications in a short time.
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Affiliation(s)
- Jeffrey L. Schloßhauer
- Fraunhofer Project Group PZ-Syn of the Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Located at the Institute of Biotechnology, Brandenburg University of Technology Cottbus-Senftenberg, 01968 Senftenberg, Germany
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg, 14476 Potsdam, Germany (S.K.)
- Laboratory of Protein Biochemistry, Institute for Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195 Berlin, Germany
| | - Srujan Kumar Dondapati
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg, 14476 Potsdam, Germany (S.K.)
| | - Stefan Kubick
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg, 14476 Potsdam, Germany (S.K.)
- Laboratory of Protein Biochemistry, Institute for Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195 Berlin, Germany
- Faculty of Health Sciences, Joint Faculty of the Brandenburg University of Technology Cottbus-Senftenberg, The Brandenburg Medical School Theodor Fontane, University of Potsdam, 14469 Potsdam, Germany
| | - Anne Zemella
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg, 14476 Potsdam, Germany (S.K.)
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van Outersterp RE, Martens J, Berden G, Steill JD, Oomens J, Rijs AM. Structural characterization of nucleotide 5'-triphosphates by infrared ion spectroscopy and theoretical studies. Phys Chem Chem Phys 2018; 20:28319-28330. [PMID: 30398499 DOI: 10.1039/c8cp03314e] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The molecular family of nucleotide triphosphates (NTPs), with adenosine 5'-triphosphate (ATP) as its best-known member, is of high biochemical importance as their phosphodiester bonds form Nature's main means to store and transport energy. Here, gas-phase IR spectroscopic studies and supporting theoretical studies have been performed on adenosine 5'-triphosphate, cytosine 5'-triphosphate and guanosine 5'-triphosphate to elucidate the intrinsic structural properties of NTPs, focusing on the influence of the nucleobase and the extent of deprotonation. Mass spectrometric studies involving collision induced dissociation showed similar fragmentation channels for the three studied NTPs within a selected charge state. The doubly charged anions exhibit fragmentation similar to the energy-releasing hydrolysis reaction in nature, while the singly charged anions show different dominant fragmentation channels, suggesting that the charge state plays a significant role in the favorability of the hydrolysis reaction. A combination of infrared ion spectroscopy and quantum-chemical computations indicates that the singly charged anions of all NTPs are preferentially deprotonated at their β-phosphates, while the doubly-charged anions are dominantly αβ-deprotonated. The assigned three-dimensional structure differs for ATP and CTP on the one hand and GTP on the other, in the sense that ATP and CTP show no interaction between nucleobase and phosphate tail, while in GTP they are hydrogen bonded. This can be rationalized by considering the structure and geometry of the NTPs where the final three dimensional structure depends on a subtle balance between hydrogen bond strength, flexibility and steric hindrance.
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Affiliation(s)
- Rianne E van Outersterp
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7, 6525ED, Nijmegen, The Netherlands.
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3
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Roux M, Dosseto A. From direct to indirect lithium targets: a comprehensive review of omics data. Metallomics 2017; 9:1326-1351. [DOI: 10.1039/c7mt00203c] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Metal ions are critical to a wide range of biological processes.
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Affiliation(s)
| | - Anthony Dosseto
- Wollongong Isotope Geochronology Laboratory
- School of Earth & Environmental Sciences
- University of Wollongong
- Wollongong
- Australia
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Gao Z, Qiu Z, Lu M, Shu J, Tang D. Hybridization chain reaction-based colorimetric aptasensor of adenosine 5'-triphosphate on unmodified gold nanoparticles and two label-free hairpin probes. Biosens Bioelectron 2016; 89:1006-1012. [PMID: 27825528 DOI: 10.1016/j.bios.2016.10.043] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 10/18/2016] [Accepted: 10/19/2016] [Indexed: 11/29/2022]
Abstract
This work designs a new label-free aptasensor for the colorimetric determination of small molecules (adenosine 5'-triphosphate, ATP) by using visible gold nanoparticles as the signal-generation tags, based on target-triggered hybridization chain reaction (HCR) between two hairpin DNA probes. The assay is carried out referring to the change in the color/absorbance by salt-induced aggregation of gold nanoparticles after the interaction with hairpins, gold nanoparticles and ATP. To construct such an assay system, two hairpin DNA probes with a short single-stranded DNA at the sticky end are utilized for interaction with gold nanoparticles. In the absence of target ATP, the hairpin DNA probes can prevent gold nanoparticles from the salt-induced aggregation through the interaction of the single-stranded DNA at the sticky end with gold nanoparticles. Upon target ATP introduction, the aptamer-based hairpin probe is opened to expose a new sticky end for the strand-displacement reaction with another complementary hairpin, thus resulting in the decreasing single-stranded DNA because of the consumption of hairpins. In this case, gold nanoparticles are uncovered owing to the formation of double-stranded DNA, which causes their aggregation upon addition of the salt, thereby leading to the change in the red-to-blue color. Under the optimal conditions, the HCR-based colorimetric assay presents good visible color or absorbance responses for the determination of target ATP at a concentration as low as 1.0nM. Importantly, the methodology can be further extended to quantitatively or qualitatively monitor other small molecules or biotoxins by changing the sequence of the corresponding aptamer.
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Affiliation(s)
- Zhuangqiang Gao
- Key Laboratory of Analysis and Detection for Food Safety (MOE & Fujian Province), Collaborative Innovation Center of Detection Technology for Haixi Food Safety and Products (Fujian Province), State Key Laboratory of Photocatalysis on Energy and Environment, Department of Chemistry, Fuzhou University, Fuzhou 350116, PR China
| | - Zhenli Qiu
- Key Laboratory of Analysis and Detection for Food Safety (MOE & Fujian Province), Collaborative Innovation Center of Detection Technology for Haixi Food Safety and Products (Fujian Province), State Key Laboratory of Photocatalysis on Energy and Environment, Department of Chemistry, Fuzhou University, Fuzhou 350116, PR China
| | - Minghua Lu
- Institute of Environmental and Analytical Science, School of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, Henan, PR China.
| | - Jian Shu
- Key Laboratory of Analysis and Detection for Food Safety (MOE & Fujian Province), Collaborative Innovation Center of Detection Technology for Haixi Food Safety and Products (Fujian Province), State Key Laboratory of Photocatalysis on Energy and Environment, Department of Chemistry, Fuzhou University, Fuzhou 350116, PR China
| | - Dianping Tang
- Key Laboratory of Analysis and Detection for Food Safety (MOE & Fujian Province), Collaborative Innovation Center of Detection Technology for Haixi Food Safety and Products (Fujian Province), State Key Laboratory of Photocatalysis on Energy and Environment, Department of Chemistry, Fuzhou University, Fuzhou 350116, PR China.
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5
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Roskoski R. Src protein-tyrosine kinase structure, mechanism, and small molecule inhibitors. Pharmacol Res 2015; 94:9-25. [PMID: 25662515 DOI: 10.1016/j.phrs.2015.01.003] [Citation(s) in RCA: 361] [Impact Index Per Article: 40.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 01/26/2015] [Indexed: 12/13/2022]
Abstract
The physiological Src proto-oncogene is a protein-tyrosine kinase that plays key roles in cell growth, division, migration, and survival signaling pathways. From the N- to C-terminus, Src contains a unique domain, an SH3 domain, an SH2 domain, a protein-tyrosine kinase domain, and a regulatory tail. The chief phosphorylation sites of human Src include an activating pTyr419 that results from phosphorylation in the kinase domain by an adjacent Src molecule and an inhibitory pTyr530 in the regulatory tail that results from phosphorylation by C-terminal Src kinase (Csk) or Chk (Csk homologous kinase). The oncogenic Rous sarcoma viral protein lacks the equivalent of Tyr530 and is constitutively activated. Inactive Src is stabilized by SH2 and SH3 domains on the rear of the kinase domain where they form an immobilizing and inhibitory clamp. Protein kinases including Src contain hydrophobic regulatory and catalytic spines and collateral shell residues that are required to assemble the active enzyme. In the inactive enzyme, the regulatory spine contains a kink or a discontinuity with a structure that is incompatible with catalysis. The conversion of inactive to active Src is accompanied by electrostatic exchanges involving the breaking and making of distinct sets of kinase domain salt bridges and hydrogen bonds. Src-catalyzed protein phosphorylation requires the participation of two Mg(2+) ions. Although nearly all protein kinases possess a common K/E/D/D signature, each enzyme exhibits its unique variations of the protein-kinase reaction template. Bosutinib, dasatinib, and ponatinib are Src/multikinase inhibitors that are approved by the FDA for the treatment of chronic myelogenous leukemia and vandetanib is approved for the treatment of medullary thyroid cancer. The Src and BCR-Abl inhibitors saracatinib and AZD0424, along with the previous four drugs, are in clinical trials for a variety of solid tumors including breast and lung cancers. Both ATP and targeted therapeutic Src protein kinase inhibitors such as dasatinib and ponatinib make hydrophobic contacts with catalytic spine residues and form hydrogen bonds with hinge residues connecting the small and large kinase lobes.
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Affiliation(s)
- Robert Roskoski
- Blue Ridge Institute for Medical Research, 3754 Brevard Road, Suite 116, Box 19, Horse Shoe, NC 28742-8814, United States.
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6
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Roskoski R. ErbB/HER protein-tyrosine kinases: Structures and small molecule inhibitors. Pharmacol Res 2014; 87:42-59. [PMID: 24928736 DOI: 10.1016/j.phrs.2014.06.001] [Citation(s) in RCA: 143] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 06/03/2014] [Accepted: 06/03/2014] [Indexed: 12/19/2022]
Abstract
The epidermal growth factor receptor (EGFR) family consists of four members that belong to the ErbB lineage of proteins (ErbB1-4). These receptors consist of an extracellular domain, a single hydrophobic transmembrane segment, and an intracellular portion with a juxtamembrane segment, a protein kinase domain, and a carboxyterminal tail. The ErbB proteins function as homo and heterodimers. Growth factor binding to EGFR induces a large conformational change in the extracellular domain. Two ligand-EGFR complexes unite to form a back-to-back dimer in which the ligands are on opposite sides of the aggregate. Following ligand binding, EGFR intracellular kinase domains form an asymmetric dimer. The carboxyterminal lobe of the activator kinase of the dimer interacts with the amino-terminal lobe of the receiver kinase thereby leading to its allosteric stimulation. Several malignancies are associated with the mutation or increased expression of members of the ErbB family including lung, breast, stomach, colorectal, head and neck, and pancreatic carcinomas. Gefitinib, erlotinib, and afatinib are orally effective protein-kinase targeted quinazoline derivatives that are used in the treatment of ERBB1-mutant lung cancer and lapatinib is an orally effective quinazoline derivative used in the treatment of ErbB2-overexpressing breast cancer. Moreover, monoclonal antibodies that target the extracellular domain of ErbB2 are used for the treatment of ErbB2-positive breast cancer and monoclonal antibodies that target ErbB1 and are used for the treatment of colorectal cancer. Cancers treated with these targeted drugs eventually become resistant to them, and a current goal of research is to develop drugs that are effective against drug-resistant tumors.
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Affiliation(s)
- Robert Roskoski
- Blue Ridge Institute for Medical Research, 3754 Brevard Road, Suite 116, Box 19, Horse Shoe, NC 28742, USA.
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7
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Wu L, Luthringer BJ, Feyerabend F, Schilling AF, Willumeit R. Effects of extracellular magnesium on the differentiation and function of human osteoclasts. Acta Biomater 2014; 10:2843-54. [PMID: 24531013 DOI: 10.1016/j.actbio.2014.02.010] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 01/25/2014] [Accepted: 02/03/2014] [Indexed: 10/25/2022]
Abstract
Magnesium-based implants have been shown to influence the surrounding bone structure. In an attempt to partially reveal the cellular mechanisms involved in the remodelling of magnesium-based implants, the influence of increased extracellular magnesium content on human osteoclasts was studied. Peripheral blood mononuclear cells were driven towards an osteoclastogenesis pathway via stimulation with receptor activator of nuclear factor kappa-B ligand and macrophage colony-stimulating factor for 28 days. Concomitantly, the cultures were exposed to variable magnesium concentrations (from either magnesium chloride or magnesium extracts). Osteoclast proliferation and differentiation were evaluated based on cell metabolic activity, total protein content, tartrate-resistant acid phosphatase activity, cathepsin K and calcitonin receptor immunocytochemistry, and cellular ability to form resorption pits. While magnesium chloride first enhanced and then opposed cell proliferation and differentiation in a concentration-dependent manner (peaking between 10 and 15mM magnesium chloride), magnesium extracts (with lower magnesium contents) appeared to decrease cell metabolic activity (≈50% decrease at day 28) while increasing osteoclast activity at a lower concentration (twofold higher). Together, the results indicated that (i) variations in the in vitro extracellular magnesium concentration affect osteoclast metabolism and (ii) magnesium extracts should be used preferentially in vitro to more closely mimic the in vivo environment.
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Li RW, Kirkland NT, Truong J, Wang J, Smith PN, Birbilis N, Nisbet DR. The influence of biodegradable magnesium alloys on the osteogenic differentiation of human mesenchymal stem cells. J Biomed Mater Res A 2014; 102:4346-57. [PMID: 24677428 DOI: 10.1002/jbm.a.35111] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Revised: 01/02/2014] [Accepted: 02/07/2014] [Indexed: 01/08/2023]
Abstract
The postdegradation effect of pure Mg, Mg-1Y, Mg-5Al, and Mg-2Ca alloys on the differentiation, proliferation and gene expression of human mesenchymal stem cells (hMSCs) was investigated. It was revealed that that Mg(2+) ions result in an increase in cell proliferation. However, we observed a maximum concentration (approximately 8.0 × 10(-4) M) that was favourable to ATP production, above which ATP production began to decrease. In contrast to proliferation, no maximum concentration for osteogenic differentiation was observed, with increasing concentration of Mg(2+) ions resulting in an increase in osteogenic differentiation across the entire tested range. Interestingly, the Mg-2Ca alloy had minimal effect on osteogenic differentiation, with Mg-1Y and pure Mg having a superior effect on the proliferation and differentiation of hMSCs. This was also observed from gene expression data, where these alloys upregulated TGFβ-1, SMAD4, FGF-2, FGF-10, and BMP-2, while SOX-2, SOX-9, and TNF-α were downregulated. Increased expression of TGFβ-1, SMAD4, BMPs, and COLIA1 protein provided further evidence to support osteogenic differentiation and that the influence of the alloying extracts on differentiation may be via the SMAD signaling pathway.
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Affiliation(s)
- Rachel W Li
- The Medical School, The Australian National University, Acton, ACT 0200, Australia; John Curtin School of Medical Research, The Australian National University, Acton, ACT 0200, Australia
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9
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Bassam R, Digel I, Hescheler J, Artmann AT, Artmann GM. Effects of spermine NONOate and ATP on protein aggregation: light scattering evidences. BMC BIOPHYSICS 2013; 6:1. [PMID: 23289636 PMCID: PMC3561150 DOI: 10.1186/2046-1682-6-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2012] [Accepted: 12/18/2012] [Indexed: 11/10/2022]
Abstract
UNLABELLED BACKGROUND AND OBJECTIVE Regulating protein function in the cell by small molecules, provide a rapid, reversible and tunable tool of metabolic control. However, due to its complexity the issue is poorly studied so far. The effects of small solutes on protein behavior can be studied by examining changes of protein secondary structure, in its hydrodynamic radius as well as its thermal aggregation. The study aim was to investigate effects of adenosine-5'-triphosphate (ATP), spermine NONOate (NO donor) as well as sodium/potassium ions on thermal aggregation of albumin and hemoglobin. To follow aggregation of the proteins, their diffusion coefficients were measured by quasi-elastic light scattering (QELS) at constant pH (7.4) in the presence of solutes over a temperature range from 25°C to 80°C. RESULTS AND DISCUSSION 1) Spermine NONOate persistently decreased the hemoglobin aggregation temperature Tairrespectively of the Na+/K+ environment, 2) ATP alone had no effect on the protein's thermal stability but it facilitated protein's destabilization in the presence of spermine NONOate and 3) mutual effects of ATP and NO were strongly influenced by particular buffer ionic compositions. CONCLUSION The ATP effect on protein aggregation was ambiguous: ATP alone had no effect on the protein's thermal stability but it facilitated protein's destabilization in the presence of nitric oxide. The magnitude and direction of the observed effects strongly depended on concentrations of K+ and Na+ in the solution.
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Affiliation(s)
- Rasha Bassam
- Institute of Bioengineering (IFB), Aachen University of Applied Sciences, 52428 Juelich, Germany.
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Jacobsen D, Bao ZQ, O’Brien P, Brooks CL, Young MA. Price to be paid for two-metal catalysis: magnesium ions that accelerate chemistry unavoidably limit product release from a protein kinase. J Am Chem Soc 2012; 134:15357-70. [PMID: 22891849 PMCID: PMC3446636 DOI: 10.1021/ja304419t] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Indexed: 11/28/2022]
Abstract
Incorporation of divalent metal ions into an active site is a fundamental catalytic tool used by diverse enzymes. Divalent cations are used by protein kinases to both stabilize ATP binding and accelerate chemistry. Kinetic analysis establishes that Cyclin-dependent kinase 2 (CDK2) requires simultaneous binding of two Mg(2+) ions for catalysis of phosphoryl transfer. This tool, however, comes with a price: the rate-acceleration effects are opposed by an unavoidable rate-limiting consequence of the use of two Mg(2+) ions by CDK2. The essential metal ions stabilize ADP product binding and limit the overall rate of the reaction. We demonstrate that product release is rate limiting for activated CDK2 and evaluate the effects of the two catalytically essential Mg(2+) ions on the stability of the ADP product within the active site. We present two new crystal structures of CDK2 bound to ADP showing how the phosphate groups can be coordinated by either one or two Mg(2+) ions, with the occupancy of one site in a weaker equilibrium. Molecular dynamics simulations indicate that ADP phosphate mobility is more restricted when ADP is coordinated by two Mg(2+) ions compared to one. The structural similarity between the rigid ADP·2Mg product and the cooperatively assembled transition state provides a mechanistic rational for the rate-limiting ADP release that is observed. We demonstrate that although the simultaneous binding of two Mg(2+) ions is essential for efficient phosphoryl transfer, the presence of both Mg(2+) ions in the active site also cooperatively increases ADP affinity and opposes its release. Evolution of protein kinases must have involved careful tuning of the affinity for the second Mg(2+) ion in order to balance the needs to stabilize the chemical transition state and allow timely product release. The link between Mg(2+) site affinity and activity presents a chemical handle that may be used by regulatory factors as well as explain some mutational effects.
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Affiliation(s)
- Douglas
M. Jacobsen
- Department of Computational Medicine and Bioinformatics, Department of Pharmacology, Department of Biological
Chemistry, Department of Chemistry, Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109,
United States
| | - Zhao-Qin Bao
- Department of Computational Medicine and Bioinformatics, Department of Pharmacology, Department of Biological
Chemistry, Department of Chemistry, Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109,
United States
| | - Patrick O’Brien
- Department of Computational Medicine and Bioinformatics, Department of Pharmacology, Department of Biological
Chemistry, Department of Chemistry, Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109,
United States
| | - Charles L. Brooks
- Department of Computational Medicine and Bioinformatics, Department of Pharmacology, Department of Biological
Chemistry, Department of Chemistry, Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109,
United States
| | - Matthew A. Young
- Department of Computational Medicine and Bioinformatics, Department of Pharmacology, Department of Biological
Chemistry, Department of Chemistry, Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109,
United States
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Bassam R, Hescheler J, Temiz-Artmann A, Artmann GM, Digel I. Effects of spermine NONOate and ATP on the thermal stability of hemoglobin. BMC BIOPHYSICS 2012; 5:16. [PMID: 22929146 PMCID: PMC3443461 DOI: 10.1186/2046-1682-5-16] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 08/17/2012] [Indexed: 12/21/2022]
Abstract
Background Minor changes in protein structure induced by small organic and inorganic molecules can result in significant metabolic effects. The effects can be even more profound if the molecular players are chemically active and present in the cell in considerable amounts. The aim of our study was to investigate effects of a nitric oxide donor (spermine NONOate), ATP and sodium/potassium environment on the dynamics of thermal unfolding of human hemoglobin (Hb). The effect of these molecules was examined by means of circular dichroism spectrometry (CD) in the temperature range between 25°C and 70°C. The alpha-helical content of buffered hemoglobin samples (0.1 mg/ml) was estimated via ellipticity change measurements at a heating rate of 1°C/min. Results Major results were: 1) spermine NONOate persistently decreased the hemoglobin unfolding temperature Tuirrespectively of the Na + /K + environment, 2) ATP instead increased the unfolding temperature by 3°C in both sodium-based and potassium-based buffers and 3) mutual effects of ATP and NO were strongly influenced by particular buffer ionic compositions. Moreover, the presence of potassium facilitated a partial unfolding of alpha-helical structures even at room temperature. Conclusion The obtained data might shed more light on molecular mechanisms and biophysics involved in the regulation of protein activity by small solutes in the cell.
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Affiliation(s)
- Rasha Bassam
- Institute of Bioengineering (IFB), Aachen University of Applied Sciences, 52428 Juelich, Germany.
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12
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Schwartz PA, Murray BW. Protein kinase biochemistry and drug discovery. Bioorg Chem 2011; 39:192-210. [PMID: 21872901 DOI: 10.1016/j.bioorg.2011.07.004] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Accepted: 07/22/2011] [Indexed: 12/19/2022]
Abstract
Protein kinases are fascinating biological catalysts with a rapidly expanding knowledge base, a growing appreciation in cell regulatory control, and an ascendant role in successful therapeutic intervention. To better understand protein kinases, the molecular underpinnings of phosphoryl group transfer, protein phosphorylation, and inhibitor interactions are examined. This analysis begins with a survey of phosphate group and phosphoprotein properties which provide context to the evolutionary selection of phosphorylation as a central mechanism for biological regulation of most cellular processes. Next, the kinetic and catalytic mechanisms of protein kinases are examined with respect to model aqueous systems to define the elements of catalysis. A brief structural biology overview further delves into the molecular basis of catalysis and regulation of catalytic activity. Concomitant with a prominent role in normal physiology, protein kinases have important roles in the disease state. To facilitate effective kinase drug discovery, classic and emerging approaches for characterizing kinase inhibitors are evaluated including biochemical assay design, inhibitor mechanism of action analysis, and proper kinetic treatment of irreversible inhibitors. As the resulting protein kinase inhibitors can modulate intended and unintended targets, profiling methods are discussed which can illuminate a more complete range of an inhibitor's biological activities to enable more meaningful cellular studies and more effective clinical studies. Taken as a whole, a wealth of protein kinase biochemistry knowledge is available, yet it is clear that a substantial extent of our understanding in this field remains to be discovered which should yield many new opportunities for therapeutic intervention.
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Affiliation(s)
- Phillip A Schwartz
- Pfizer Worldwide Research and Development, La Jolla, Pfizer Inc., San Diego, CA 92121, United States
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Brockhoff M, Hau JC, Fontana P, Zimmermann C, Pover AD, Erdmann D, Chène P. Factors influencing the inhibition of protein kinases. J Enzyme Inhib Med Chem 2011; 27:194-200. [PMID: 21635207 DOI: 10.3109/14756366.2011.583922] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The protein kinase field is a very active research area in the pharmaceutical industry and many activities are ongoing to identify inhibitors of these proteins. The design of new chemical entities with improved pharmacological properties requires a deeper understanding of the factors that modulate inhibitor-kinase interactions. In this report, we studied the effect of two of these factors--the magnesium ion cofactor and the protein substrate--on inhibitors of the type I insulin-like growth factor receptor. Our results show that the concentration of magnesium ion influences the potency of adenosine triphosphate (ATP) competitive inhibitors, suggesting an explanation for the observation that such compounds retain their nanomolar potency in cells despite the presence of millimolar levels of ATP. We also showed that the peptidic substrate affects the potency of these inhibitors in a different manner, suggesting that the influence of this substrate on compound potency should be taken into consideration during drug discovery.
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Affiliation(s)
- Marielle Brockhoff
- Druggability-Enzymology-Profiling Unit, Oncology Research, Novartis Institutes of BioMedical Research, Basel, Switzerland
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14
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Covy JP, Giasson BI. The G2019S pathogenic mutation disrupts sensitivity of leucine-rich repeat kinase 2 to manganese kinase inhibition. J Neurochem 2010; 115:36-46. [PMID: 20626563 DOI: 10.1111/j.1471-4159.2010.06894.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mutations in leucine-rich repeat kinase-2 (LRRK2) are the most common cause of late-onset Parkinson disease. Previously, we showed that the G2019S pathogenic mutation can cause a dramatic increase (approximately 10-fold) in kinase activity, far above other published studies. A notable experimental difference was the use of Mn-ATP as a substrate. Therefore, the effects of metal cation-ATP cofactors on LRRK2 kinase activity were investigated. It is shown, using several divalent metal cations, that only Mg(2+) or Mn(2+) can support LRRK2 kinase activity. However, for wild-type, I2020T, and R1441C LRRK2, Mn(2+) was significantly less effective at supporting kinase activity. In sharp contrast, both Mn(2+) and Mg(2+) were effective at supporting the activity of G2019S LRRK2. These divergent effects associated with divalent cation usage and the G2019S mutation were predominantly because of differences in catalytic rates. However, LRRK2 was shown to have much lower (approximately 40-fold) ATP K(m) for Mn-ATP compared with Mg-ATP. Consequently, sub-stoichiometric concentrations of Mn(2+) can act to inhibit the kinase activity of wild-type, but not G2019S LRRK2 in the presence of Mg(2+) . From these findings, a new model is proposed for a possible function of LRRK2 and the consequence of the G2019S LRRK2 pathogenic mutation.
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Affiliation(s)
- Jason P Covy
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6084, USA
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15
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Liu M, Girma E, Glicksman MA, Stein RL. Kinetic mechanistic studies of Cdk5/p25-catalyzed H1P phosphorylation: metal effect and solvent kinetic isotope effect. Biochemistry 2010; 49:4921-9. [PMID: 20491486 DOI: 10.1021/bi100244j] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cdk5/p25 is a member of the cyclin-dependent, Ser/Thr kinase family and has been identified as one of the principle Alzheimer's disease-associated kinases that promote the formation of hyperphosphorylated tau, the major component of neurofibrillary tangles. We and others have been developing inhibitors of cdk5/p25 as possible therapeutic agents for Alzheimer's disease (AD). In support of these efforts, we examine the metal effect and solvent kinetic isotope effect on cdk5/p25-catalyzed H1P (a histone H-1-derived peptide) phosphorylation. Here, we report that a second Mg(2+) in addition to the one forming the MgATP complex is required to bind to cdk5/p25 for its catalytic activity. It activates cdk5/p25 by demonstrating an increase in k(cat) and induces a conformational change that favors ATP binding but has no effect on the binding affinity for the H1P peptide substrate. The binding of the second Mg(2+) does not change the binding order of substrates. The reaction follows the same rapid equilibrium random mechanism in the presence or absence of the second Mg(2+) as evidenced by initial velocity analysis and substrate analogue and product inhibition studies. A linear proton inventory with a normal SKIE of 2.0 +/- 0.1 in the presence of the second Mg(2+) was revealed and suggested a single proton transfer in the rate-limiting phosphoryl transfer step. The pH profile revealed a residue with a pK(a) of 6.5 that is most likely the general acid-base catalyst facilitating the proton transfer.
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Affiliation(s)
- Min Liu
- Laboratory for Drug Discovery in Neurodegeneration, Harvard NeuroDiscovery Center, 65 Landsdowne Street, Fourth Floor, Cambridge, Massachusetts 02139, USA.
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16
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Mukherjee K, Sharma M, Jahn R, Wahl MC, Südhof TC. Evolution of CASK into a Mg2+-sensitive kinase. Sci Signal 2010; 3:ra33. [PMID: 20424264 DOI: 10.1126/scisignal.2000800] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
All known protein kinases, except CASK [calcium/calmodulin (CaM)-activated serine-threonine kinase], require magnesium ions (Mg(2+)) to stimulate the transfer of a phosphate from adenosine 5'-triphosphate (ATP) to a protein substrate. The CaMK (calcium/calmodulin-dependent kinase) domain of CASK shows activity in the absence of Mg(2+); indeed, it is inhibited by divalent ions including Mg(2+). Here, we converted the Mg(2+)-inhibited wild-type CASK kinase (CASK(WT)) into a Mg(2+)-stimulated kinase (CASK(4M)) by substituting four residues within the ATP-binding pocket. Crystal structures of CASK(4M) with and without bound nucleotide and Mn(2+), together with kinetic analyses, demonstrated that Mg(2+) accelerates catalysis of CASK(4M) by stabilizing the transition state, enhancing the leaving group properties of adenosine 5'-diphosphate, and indirectly shifting the position of the gamma-phosphate of ATP. Phylogenetic analysis revealed that the four residues conferring Mg(2+)-mediated stimulation were substituted from CASK during early animal evolution, converting a primordial, Mg(2+)-coordinating form of CASK into a Mg(2+)-inhibited kinase. This emergence of Mg(2+) sensitivity (inhibition by Mg(2+)) conferred regulation of CASK activity by divalent cations, in parallel with the evolution of the animal nervous systems.
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Affiliation(s)
- Konark Mukherjee
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 1050 Arastradero Road, Palo Alto, CA 94304, USA.
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17
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Hekmat-Nejad M, Cai T, Swinney DC. Steady-state kinetic characterization of kinase activity and requirements for Mg2+ of interleukin-1 receptor-associated kinase-4. Biochemistry 2010; 49:1495-506. [PMID: 20104875 DOI: 10.1021/bi901609m] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Interleukin-1 receptor-associated kinase-4 (IRAK-4) is a Ser/Thr-specific protein kinase that plays a critical role in intracellular signaling cascades mediated by Toll-like and interleukin-1 (IL-1) receptors. Despite a growing body of information on the physiological functions of IRAK-4, its kinase activity remains poorly studied. The present study entails characterization of the steady-state kinetic properties and Mg(2+) requirements of full-length, recombinant human IRAK-4 preactivated by incubation with MgATP. In the presence of 20 mM Mg(2+), activated IRAK-4 herein is demonstrated to phosphorylate a peptide substrate (IRAK-1 peptide), derived from the activation loop of IRAK-1, with a k(cat) of 30 +/- 2.9 s(-1) and K(m) values of 668 +/- 120 and 852 +/- 273 microM for ATP and the peptide, respectively. Two-substrate, dead-end and product inhibition data, using analogues of ATP, are consistent with both a sequential ordered kinetic mechanism with ATP binding to the enzyme prior to the peptide and a sequential random mechanism. Investigation of the Mg(2+) requirements for phosphoryl transfer activity of IRAK-4 revealed that more than one Mg(2+) ion interacts with the enzyme and that the enzyme is maximally active in the presence of 5-10 mM free Mg(2+). While one divalent metal, as part of a chelate complex with ATP, is essential for catalysis, kinetic evidence is provided to show that uncomplexed Mg(2+) further enhances the catalytic activity of IRAK-4 by bringing about an approximately 3-fold increase in k(cat) and an approximately 6-fold reduction in the K(m) for ATP and by rendering the interaction between the nucleotide and peptide substrate binding sites less antagonistic.
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Affiliation(s)
- Mohammad Hekmat-Nejad
- Department of Virology, Roche Palo Alto, LLC, 3431 Hillview Avenue, Palo Alto, California 94304, USA.
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18
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Chilin A, Conconi MT, Marzaro G, Guiotto A, Urbani L, Tonus F, Parnigotto P. Exploring Epidermal Growth Factor Receptor (EGFR) Inhibitor Features: The Role of Fused Dioxygenated Rings on the Quinazoline Scaffold. J Med Chem 2010; 53:1862-6. [DOI: 10.1021/jm901338g] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Adriana Chilin
- Dipartimento di Scienze Farmaceutiche, Università di Padova, via Marzolo 5, 35131 Padova, Italy
| | - Maria Teresa Conconi
- Dipartimento di Scienze Farmaceutiche, Università di Padova, via Marzolo 5, 35131 Padova, Italy
| | - Giovanni Marzaro
- Dipartimento di Scienze Farmaceutiche, Università di Padova, via Marzolo 5, 35131 Padova, Italy
| | - Adriano Guiotto
- Dipartimento di Scienze Farmaceutiche, Università di Padova, via Marzolo 5, 35131 Padova, Italy
| | - Luca Urbani
- Dipartimento di Scienze Farmaceutiche, Università di Padova, via Marzolo 5, 35131 Padova, Italy
| | - Francesca Tonus
- Dipartimento di Scienze Farmaceutiche, Università di Padova, via Marzolo 5, 35131 Padova, Italy
| | - Pierpaolo Parnigotto
- Dipartimento di Scienze Farmaceutiche, Università di Padova, via Marzolo 5, 35131 Padova, Italy
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19
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Reddy MM, Rajasekharan R. Role of threonine residues in the regulation of manganese-dependent arabidopsis serine/threonine/tyrosine protein kinase activity. Arch Biochem Biophys 2006; 455:99-109. [PMID: 17054899 DOI: 10.1016/j.abb.2006.09.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2006] [Revised: 09/13/2006] [Accepted: 09/13/2006] [Indexed: 11/18/2022]
Abstract
Tyrosine phosphorylation in plants could be performed only by dual-specificity kinases. Arabidopsis thaliana dual-specificity protein kinase (AtSTYPK) exhibited strong preference for manganese over magnesium for its kinase activity. The kinase autophosphorylated on serine, threonine and tyrosine residues and phosphorylated myelin basic protein on threonine and tyrosine residues. The AtSTYPK harbors manganese dependent serine/threonine kinase domain, COG3642. His248 and Ser265 on COG3642 are conserved in AtSTYPK and the site-directed mutant, H248A showed loss of serine/threonine kinase activity. The protein kinase activity was abolished when Thr208 in the TEY motif and Thr293 of the activation loop were converted to alanine. The conversion of Thr284 in the activation loop to alanine resulted in an increased phosphorylation. This study reports the first identification of a manganese dependent dual-specificity kinase and the importance of Thr208, Thr284, and Thr293 residues in the regulation of kinase activity.
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Affiliation(s)
- Mamatha M Reddy
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
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20
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Lin X, Ayrapetov MK, Sun G. Characterization of the interactions between the active site of a protein tyrosine kinase and a divalent metal activator. BMC BIOCHEMISTRY 2005; 6:25. [PMID: 16305747 PMCID: PMC1316873 DOI: 10.1186/1471-2091-6-25] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2005] [Accepted: 11/23/2005] [Indexed: 11/10/2022]
Abstract
BACKGROUND Protein tyrosine kinases are important enzymes for cell signalling and key targets for anticancer drug discovery. The catalytic mechanisms of protein tyrosine kinase-catalysed phosphorylation are not fully understood. Protein tyrosine kinase Csk requires two Mg2+ cations for activity: one (M1) binds to ATP, and the other (M2) acts as an essential activator. RESULTS Experiments in this communication characterize the interaction between M2 and Csk. Csk activity is sensitive to pH in the range of 6 to 7. Kinetic characterization indicates that the sensitivity is not due to altered substrate binding, but caused by the sensitivity of M2 binding to pH. Several residues in the active site with potential of binding M2 are mutated and the effect on metal activation studied. An active mutant of Asn319 is generated, and this mutation does not alter the metal binding characteristics. Mutations of Glu236 or Asp332 abolish the kinase activity, precluding a positive or negative conclusion on their role in M2 coordination. Finally, the ability of divalent metal cations to activate Csk correlates to a combination of ionic radius and the coordination number. CONCLUSION These studies demonstrate that M2 binding to Csk is sensitive to pH, which is mainly responsible for Csk activity change in the acidic arm of the pH response curve. They also demonstrate critical differences in the metal activator coordination sphere in protein tyrosine kinase Csk and a protein Ser/Thr kinase, the cAMP-dependent protein kinase. They shed light on the physical interactions between a protein tyrosine kinase and a divalent metal activator.
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Affiliation(s)
- Xiaofeng Lin
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI 02881, USA
| | - Marina K Ayrapetov
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI 02881, USA
| | - Gongqin Sun
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI 02881, USA
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21
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Ayrapetov MK, Lee S, Sun G. Expression, purification, and biochemical characterization of Chk, a soluble protein tyrosine kinase. Protein Expr Purif 2003; 29:148-55. [PMID: 12767803 DOI: 10.1016/s1046-5928(02)00698-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
CSK family contains two protein tyrosine kinases: Csk (C-terminal Src kinase) and Chk (Csk homologous kinase). They are responsible for phosphorylating Src family protein tyrosine kinases on a C-terminal Tyr (Tyr527) and negatively regulating their activities. However, Chk and Csk have different expression patterns, mechanisms of regulation, and different biological functions, and appear to play different roles in the development of breast cancer. To obtain pure human Chk for biochemical characterization, its coding region was amplified by polymerase chain reaction and expressed as a fusion protein with glutathione S-transferase in Escherichia coli. The enzyme was highly expressed but unusually prone to proteolytic degradation during purification. Expression of the enzyme as a dual fusion protein with glutathione S-transferase on N-terminus and streptag, a 10 amino acid peptide, on C-terminus allowed purification of the full-length fusion protein. The purified enzyme was able to phosphorylate and inactivate Src. Chk (no inhibition up to 18.5 microM) and Csk (IC(50)= 1 microM) were differentially inhibited by PP2, probably due to the size difference of one residue (Thr265 in Csk versus Met304 in Chk) in the ATP-binding domain. The expression, purification, and initial characterizations of Chk provided an important step toward full characterization of Chk and Csk, two important enzymes in cellular regulation.
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Affiliation(s)
- Marina K Ayrapetov
- Department of Cell and Molecular Biology, University of Rhode Island, 117 Morrill Hall, 45 Lower College Road, Kingston, RI 02881, USA
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22
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Affiliation(s)
- J A Adams
- Department of Pharmacology, University of California, San Diego, La Jolla, California 92093-0506, USA.
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23
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Frankel M, Ablooglu AJ, Leone JW, Rusinova E, Ross JB, Heinrikson RL, Kohanski RA. Intrasteric inhibition of ATP binding is not required to prevent unregulated autophosphorylation or signaling by the insulin receptor. Mol Cell Biol 2001; 21:4197-207. [PMID: 11390649 PMCID: PMC87081 DOI: 10.1128/mcb.21.13.4197-4207.2001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Receptor tyrosine kinases may use intrasteric inhibition to suppress autophosphorylation prior to growth factor stimulation. To test this hypothesis we made an Asp1161Ala mutant in the activation loop that relieved intrasteric inhibition of the unphosphorylated insulin receptor (IR) and its recombinant cytoplasmic kinase domain (IRKD) without affecting the activated state. Solution studies with the unphosphorylated mutant IRKD demonstrated conformational changes and greater catalytic efficiency from a 10-fold increase in k(cat) and a 15-fold-lower K(m ATP) although K(m peptide) was unchanged. Kinetic parameters of the autophosphorylated mutant and wild-type kinase domains were virtually identical. The Asp1161Ala mutation increased the rate of in vitro autophosphorylation of the IRKD or IR at low ATP concentrations and in the absence of insulin. However, saturation with ATP (for the IRKD) or the presence of insulin (for the IR) yielded equivalent rates of autophosphorylation for mutant versus wild-type kinases. Despite a biochemically more active kinase domain, the mutant IR expressed in C2C12 myoblasts was not constitutively autophosphorylated. However, it displayed a 2.5-fold-lower 50% effective concentration for insulin stimulation of autophosphorylation and was dephosphorylated more slowly following withdrawal of insulin than wild-type IR. In tests of the regulation of the unphosphorylated basal state, these results demonstrate that neither intrasteric inhibition against ATP binding nor suppression of kinase activity is required to prevent premature autophosphorylation of the IR. Finally, the lower rate of dephosphorylation suggests invariant residues of the activation loop such as Asp1161 may function at multiple junctures in cellular regulation of receptor tyrosine kinases.
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Affiliation(s)
- M Frankel
- Department of Biochemistry and Molecular Biology, Mount Sinai School of Medicine, New York, New York 10029, USA
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Sun G, Budde RJ. Affinity purification of Csk protein tyrosine kinase based on its catalytic requirement for divalent metal cations. Protein Expr Purif 2001; 21:8-12. [PMID: 11162381 DOI: 10.1006/prep.2000.1351] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Protein tyrosine kinase Csk requires two Mg2+ ions for activity: one magnesium is part of the ATP-Mg complex, and the second free Mg2+ ion is required as an essential activator. Zn2+ can bind to this site to replace Mg2+, which inhibits Csk kinase activity. The binding is reversible and removal of Zn2+ results in an active Csk apoenzyme. In this communication, we report that this tight binding can be used as a mechanism for affinity purification of Csk. When bacterial cell lysate containing overexpressed GST-Csk was applied to a column of Zn2+-iminodiacetic acid immobilized to agarose, Csk was specifically retained by the column. Since the binding of Csk to Zn2+ is not affected by up to 200 mM NaCl, high ionic strength conditions were used in the purification procedure, minimizing nonspecific binding due to ionic interactions. Washing the column with 200 mM NaCl and 50 mM imidazole removed virtually all other proteins from the column while Csk remained bound. The retained Csk enzyme was eluted with 1 M imidazole. The 1 M imidazole-eluted fraction contained pure Csk that had a specific activity similar to the enzyme purified by a glutathione-agarose affinity column.
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Affiliation(s)
- G Sun
- Department of Neuro-Oncology, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA
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