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Davulcu O, Peng Y, Brüschweiler R, Skalicky JJ, Chapman MS. Elevated μs-ms timescale backbone dynamics in the transition state analog form of arginine kinase. J Struct Biol 2017; 200:258-266. [PMID: 28495594 DOI: 10.1016/j.jsb.2017.05.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 05/04/2017] [Accepted: 05/06/2017] [Indexed: 10/19/2022]
Abstract
Arginine kinase catalyzes reversible phosphoryl transfer between arginine and ATP. Crystal structures of arginine kinase in an open, substrate-free form and closed, transition state analog (TSA) complex indicate that the enzyme undergoes substantial domain and loop rearrangements required for substrate binding, catalysis, and product release. Nuclear magnetic resonance (NMR) has shown that substrate-free arginine kinase is rigid on the ps-ns timescale (average S2=0.84±0.08) yet quite dynamic on the µs-ms timescale (35 residues with Rex, 12%), and that movements of the N-terminal domain and the loop comprising residues I182-G209 are rate-limiting on catalysis. Here, NMR of the TSA-bound enzyme shows similar rigidity on the ps-ns timescale (average S2=0.91±0.05) and substantially increased μs-ms timescale dynamics (77 residues; 22%). Many of the residues displaying μs-ms dynamics in NMR Carr-Purcell-Meiboom-Gill (CPMG) 15N backbone relaxation dispersion experiments of the TSA complex are also dynamic in substrate-free enzyme. However, the presence of additional dynamic residues in the TSA-bound form suggests that dynamics extend through much of the C-terminal domain, which indicates that in the closed form, a larger fraction of the protein takes part in conformational transitions to the excited state(s). Conformational exchange rate constants (kex) of the TSA complex are all approximately 2500s-1, higher than any observed in the substrate-free enzyme (800-1900s-1). Elevated μs-ms timescale protein dynamics in the TSA-bound enzyme is more consistent with recently postulated catalytic networks involving multiple interconnected states at each step of the reaction, rather than a classical single stabilized transition state.
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Affiliation(s)
- Omar Davulcu
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, OR 97239, United States
| | - Yu Peng
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, United States
| | - Rafael Brüschweiler
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, United States; Department of Biological Chemistry and Pharmacology and Campus Chemical Instrument Center, The Ohio State University, OH 43210, United States
| | - Jack J Skalicky
- Department of Biochemistry, University of Utah, Salt Lake City, UT 84112, United States
| | - Michael S Chapman
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, OR 97239, United States.
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2
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Peng Y, Hansen AL, Bruschweiler-Li L, Davulcu O, Skalicky JJ, Chapman MS, Brüschweiler R. The Michaelis Complex of Arginine Kinase Samples the Transition State at a Frequency That Matches the Catalytic Rate. J Am Chem Soc 2017; 139:4846-4853. [PMID: 28287709 DOI: 10.1021/jacs.7b00236] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Arginine kinase (AK), which is a member of the phosphagen kinase family, serves as a model system for studying the structural and dynamic determinants of biomolecular enzyme catalysis of all major states involved of the enzymatic cycle. These states are the apo state (substrate free), the Michaelis complex analogue AK:Arg:Mg·AMPPNP (MCA), a product complex analogue AK:pAIE:Mg·ADP (PCA), and the transition state analogue AK:Arg:Mg·ADP:NO3- (TSA). The conformational dynamics of these states have been studied by NMR relaxation dispersion measurements of the methyl groups of the Ile, Leu, and Val residues at two static magnetic fields. Although all states undergo significant amounts of μs-ms time scale dynamics, only the MCA samples a dominant excited state that resembles the TSA, as evidenced by the strong correlation between the relaxation dispersion derived chemical shift differences Δω and the equilibrium chemical shift differences Δδ of these states. The average lifetime of the MCA is 36 ms and the free energy difference to the TSA-like form is 8.5 kJ/mol. It is shown that the conformational energy landscape of the Michaelis complex analogue is shaped in a way that at room temperature it channels passage to the transition state, thereby determining the rate-limiting step of the phosphorylation reaction of arginine. Conversely, relaxation dispersion experiments of the TSA reveal that it samples the structures of the Michaelis complex analogue or the apo state as its dominant excited state. This reciprocal behavior shows that the free energy of the TSA, with all ligands bound, is lower by only about 8.9 kJ/mol than that of the Michaelis or apo complex conformations with the TSA ligands present.
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Affiliation(s)
| | | | | | - Omar Davulcu
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University , Portland, Oregon 97239, United States
| | - Jack J Skalicky
- Department of Biochemistry, University of Utah , Salt Lake City, Utah 84112, United States
| | - Michael S Chapman
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University , Portland, Oregon 97239, United States
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3
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Ozgur B, Ozdemir ES, Gursoy A, Keskin O. Relation between Protein Intrinsic Normal Mode Weights and Pre-Existing Conformer Populations. J Phys Chem B 2017; 121:3686-3700. [DOI: 10.1021/acs.jpcb.6b10401] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Beytullah Ozgur
- Center for Computational Biology and Bioinformatics, ‡Chemical and Biological
Engineering, and §Computer Engineering,
College of Engineering, Koc University, 34450 Istanbul, Turkey
| | - E. Sila Ozdemir
- Center for Computational Biology and Bioinformatics, ‡Chemical and Biological
Engineering, and §Computer Engineering,
College of Engineering, Koc University, 34450 Istanbul, Turkey
| | - Attila Gursoy
- Center for Computational Biology and Bioinformatics, ‡Chemical and Biological
Engineering, and §Computer Engineering,
College of Engineering, Koc University, 34450 Istanbul, Turkey
| | - Ozlem Keskin
- Center for Computational Biology and Bioinformatics, ‡Chemical and Biological
Engineering, and §Computer Engineering,
College of Engineering, Koc University, 34450 Istanbul, Turkey
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4
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Godsey MH, Davulcu O, Nix JC, Skalicky JJ, Brüschweiler RP, Chapman MS. The Sampling of Conformational Dynamics in Ambient-Temperature Crystal Structures of Arginine Kinase. Structure 2016; 24:1658-1667. [PMID: 27594681 DOI: 10.1016/j.str.2016.07.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 07/01/2016] [Accepted: 07/06/2016] [Indexed: 01/26/2023]
Abstract
Arginine kinase provides a model for functional dynamics, studied through crystallography, enzymology, and nuclear magnetic resonance. Structures are now solved, at ambient temperature, for the transition state analog (TSA) complex. Analysis of quasi-rigid sub-domain displacements show that differences between the two TSA structures average about 5% of changes between substrate-free and TSA forms, and they are nearly co-linear. Small backbone hinge rotations map to sites that also flex on substrate binding. Anisotropic atomic displacement parameters (ADPs) are refined using rigid-body TLS constraints. Consistency between crystal forms shows that they reflect intrinsic molecular properties more than crystal lattice effects. In many regions, the favored directions of thermal/static displacement are appreciably correlated with movements on substrate binding. Correlation between ADPs and larger substrate-associated movements implies that the latter approximately follow paths of low-energy intrinsic motions.
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Affiliation(s)
- Michael H Godsey
- Department of Math/Science, Concordia University, Portland, OR 97211, USA
| | - Omar Davulcu
- Department Biochemistry and Molecular Biology, School of Medicine, Oregon Health & Science University, Portland, OR 97239, USA
| | - Jay C Nix
- Molecular Biology Consortium, Lawrence Berkeley Natl. Lab., Berkeley, CA 94720, USA
| | - Jack J Skalicky
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 8412, USA
| | - Rafael P Brüschweiler
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH 43210, USA
| | - Michael S Chapman
- Department Biochemistry and Molecular Biology, School of Medicine, Oregon Health & Science University, Portland, OR 97239, USA.
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5
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Karmakar T, Roy S, Balaram H, Balasubramanian S. Structural and dynamical correlations in PfHGXPRT oligomers: A molecular dynamics simulation study. J Biomol Struct Dyn 2016; 34:1590-605. [PMID: 26441001 DOI: 10.1080/07391102.2015.1085441] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
PfHGXPRT is a key enzyme involved in purine nucleotide salvage pathway of the malarial parasite, Plasmodium falciparum. Atomistic molecular dynamics simulations have been performed on two types of PfHGXPRT dimers (D1 and D3) and its tetramer in their apo and ligand-bound states. A significant event in the catalytic cycle is the dynamics of a gate that provides access for the ligand molecules to the reaction center. The gate is formed by loops II and IV, the former being the most flexible. Large amplitude conformational changes have been observed in active site loop II. Upon complete occupancy of the active site, loop II gets stabilized due to specific interactions between its residues and the ligand molecules. Remote loop, X, is seen to be less fluxional in the D3 dimer than in D1 which is rationalized as due to the greater number of inter-subunit contacts in the former. The presence of ligand molecules in subunits of the tetramer further reduces the flexibility of loop X epitomizing a communication between this region and the active sites in the tetramer. These observations are in accordance with the outcomes of several experimental investigations. Participation of loop X in the oligomerization process has also been discerned. Between the two types of dimers in solution, D1 tetramerizes readily and thus would not be present as free dimers. We conjecture an equilibrium to exist between D3 and the tetramer in solution; upon binding of the ligand molecules to the D3 dimer, this equilibrium shifts toward the tetramer.
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Affiliation(s)
- Tarak Karmakar
- a Chemistry and Physics of Materials Unit , Jawaharlal Nehru Centre for Advanced Scientific Research , Bangalore , 560 064 India
| | - Sourav Roy
- b Molecular Biology and Genetics Unit , Jawaharlal Nehru Centre for Advanced Scientific Research , Bangalore , 560 064 India
| | - Hemalatha Balaram
- b Molecular Biology and Genetics Unit , Jawaharlal Nehru Centre for Advanced Scientific Research , Bangalore , 560 064 India
| | - Sundaram Balasubramanian
- a Chemistry and Physics of Materials Unit , Jawaharlal Nehru Centre for Advanced Scientific Research , Bangalore , 560 064 India
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6
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Lisi GP, Loria JP. Using NMR spectroscopy to elucidate the role of molecular motions in enzyme function. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2016; 92-93:1-17. [PMID: 26952190 PMCID: PMC4785347 DOI: 10.1016/j.pnmrs.2015.11.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 11/18/2015] [Accepted: 11/19/2015] [Indexed: 05/04/2023]
Abstract
Conformational motions play an essential role in enzyme function, often facilitating the formation of enzyme-substrate complexes and/or product release. Although considerable debate remains regarding the role of molecular motions in the conversion of enzymatic substrates to products, numerous examples have found motions to be crucial for optimization of enzyme scaffolds, effective substrate binding, and product dissociation. Conformational fluctuations are often rate-limiting to enzyme catalysis, primarily through product release, with the chemical reaction occurring much more quickly. As a result, the direct involvement of motions at various stages along the enzyme reaction coordinate remains largely unknown and untested. In the following review, we describe the use of solution NMR techniques designed to probe various timescales of molecular motions and detail examples in which motions play a role in propagating catalytic effects from the active site and directly participate in essential aspects of enzyme function.
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Affiliation(s)
- George P Lisi
- Department of Chemistry, Yale University, New Haven, CT 06520, United States
| | - J Patrick Loria
- Department of Chemistry, Yale University, New Haven, CT 06520, United States; Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, United States.
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Wang Z, Qiao Z, Ye S, Zhang R. Structure of a double-domain phosphagen kinase reveals an asymmetric arrangement of the tandem domains. ACTA ACUST UNITED AC 2015; 71:779-89. [PMID: 25849389 DOI: 10.1107/s1399004715001169] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 01/20/2015] [Indexed: 12/27/2022]
Abstract
Tandem duplications and fusions of single genes have led to magnificent expansions in the divergence of protein structures and functions over evolutionary timescales. One of the possible results is polydomain enzymes with interdomain cooperativities, few examples of which have been structurally characterized at the full-length level to explore their innate synergistic mechanisms. This work reports the crystal structures of a double-domain phosphagen kinase in both apo and ligand-bound states, revealing a novel asymmetric L-shaped arrangement of the two domains. Unexpectedly, the interdomain connections are not based on a flexible hinge linker but on a rigid secondary-structure element: a long α-helix that tethers the tandem domains in relatively fixed positions. Besides the connective helix, the two domains also contact each other directly and form an interdomain interface in which hydrogen bonds and hydrophobic interactions further stabilize the L-shaped domain arrangement. Molecular-dynamics simulations show that the interface is generally stable, suggesting that the asymmetric domain arrangement crystallographically observed in the present study is not a conformational state simply restrained by crystal-packing forces. It is possible that the asymmetrically arranged tandem domains could provide a structural basis for further studies of the interdomain synergy.
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Affiliation(s)
- Zhiming Wang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, People's Republic of China
| | - Zhu Qiao
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, People's Republic of China
| | - Sheng Ye
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, People's Republic of China
| | - Rongguang Zhang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, People's Republic of China
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8
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Davulcu O, Niu X, Brüschweiler-Li L, Brüschweiler R, Skalicky JJ, Chapman MS. Backbone resonance assignments of the 42 kDa enzyme arginine kinase in the transition state analogue form. BIOMOLECULAR NMR ASSIGNMENTS 2014; 8:335-338. [PMID: 23893440 PMCID: PMC3906217 DOI: 10.1007/s12104-013-9512-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Accepted: 07/21/2013] [Indexed: 06/02/2023]
Abstract
Nearly complete backbone resonance assignments for the 357 residue, 42 kDa enzyme arginine kinase in a transition state analogue (TSA) complex are presented. The TSA is a quaternary complex of arginine kinase, MgADP, arginine, and nitrate. About 93% (320 of 344) of the non-proline backbone amides were assigned using an enzyme enriched with (2)H, (13)C, and (15)N in combination with three enzyme samples prepared with a single (15)N-labeled amino acid (K, L, and R). The amide assignments will provide the foundation for investigating the dynamics of arginine kinase when in a TSA complex.
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Affiliation(s)
- Omar Davulcu
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon, 97239-3098, USA
| | - Xiaogang Niu
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA
| | - Lei Brüschweiler-Li
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA
| | - Rafael Brüschweiler
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA
| | - Jack J. Skalicky
- Department of Biochemistry, University of Utah, Salt Lake City, Utah, 84112-5650, USA
| | - Michael S. Chapman
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon, 97239-3098, USA
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9
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Summerton JC, Martin GM, Evanseck JD, Chapman MS. Common hydrogen bond interactions in diverse phosphoryl transfer active sites. PLoS One 2014; 9:e108310. [PMID: 25238155 PMCID: PMC4169622 DOI: 10.1371/journal.pone.0108310] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Accepted: 08/27/2014] [Indexed: 11/18/2022] Open
Abstract
Phosphoryl transfer reactions figure prominently in energy metabolism, signaling, transport and motility. Prior detailed studies of selected systems have highlighted mechanistic features that distinguish different phosphoryl transfer enzymes. Here, a top-down approach is developed for comparing statistically the active site configurations between populations of diverse structures in the Protein Data Bank, and it reveals patterns of hydrogen bonding that transcend enzyme families. Through analysis of large samples of structures, insights are drawn at a level of detail exceeding the experimental precision of an individual structure. In phosphagen kinases, for example, hydrogen bonds with the O3β of the nucleotide substrate are revealed as analogous to those in unrelated G proteins. In G proteins and other enzymes, interactions with O3β have been understood in terms of electrostatic favoring of the transition state. Ground state quantum mechanical calculations on model compounds show that the active site interactions highlighted in our database analysis can affect substrate phosphate charge and bond length, in ways that are consistent with prior experimental observations, by modulating hyperconjugative orbital interactions that weaken the scissile bond. Testing experimentally the inference about the importance of O3β interactions in phosphagen kinases, mutation of arginine kinase Arg280 decreases kcat, as predicted, with little impact upon KM.
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Affiliation(s)
- Jean C. Summerton
- Department of Biochemistry and Molecular Biology, School of Medicine, Oregon Health and Science University, Portland, Oregon, United States of America
| | - Gregory M. Martin
- Department of Biochemistry and Molecular Biology, School of Medicine, Oregon Health and Science University, Portland, Oregon, United States of America
| | - Jeffrey D. Evanseck
- Center for Computational Sciences and the Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania, United States of America
| | - Michael S. Chapman
- Department of Biochemistry and Molecular Biology, School of Medicine, Oregon Health and Science University, Portland, Oregon, United States of America
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10
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NMR spectroscopy on domain dynamics in biomacromolecules. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2013; 112:58-117. [DOI: 10.1016/j.pbiomolbio.2013.05.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2013] [Revised: 05/06/2013] [Accepted: 05/07/2013] [Indexed: 12/22/2022]
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Summerton JC, Evanseck JD, Chapman MS. Hyperconjugation-mediated solvent effects in phosphoanhydride bonds. J Phys Chem A 2012; 116:10209-17. [PMID: 23009395 DOI: 10.1021/jp306607k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Density functional theory and natural bond orbital analysis are used to explore the impact of solvent on hyperconjugation in methyl triphosphate, a model for "energy rich" phosphoanhydride bonds, such as found in ATP. As expected, dihedral rotation of a hydroxyl group vicinal to the phosphoanhydride bond reveals that the conformational dependence of the anomeric effect involves modulation of the orbital overlap between the donor and acceptor orbitals. However, a conformational independence was observed in the rotation of a solvent hydrogen bond. As one lone pair orbital rotates away from an optimal antiperiplanar orientation, the overall magnitude of the anomeric effect is compensated approximately by the other lone pair as it becomes more antiperiplanar. Furthermore, solvent modulation of the anomeric effect is not restricted to the antiperiplanar lone pair; hydrogen bonds involving gauche lone pairs also affect the anomeric interaction and the strength of the phosphoanhydride bond. Both gauche and anti solvent hydrogen bonds lengthen nonbridging O-P bonds, increasing the distance between donor and acceptor orbitals and decreasing orbital overlap, which leads to a reduction of the anomeric effect. Solvent effects are additive with greater reduction in the anomeric effect upon increasing water coordination. By controlling the coordination environment of substrates in an active site, kinases, phosphatases, and other enzymes important in metabolism and signaling may have the potential to modulate the stability of individual phosphoanhydride bonds through stereoelectronic effects.
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Affiliation(s)
- Jean C Summerton
- Department of Biochemistry & Molecular Biology, School of Medicine, Oregon Health & Science University, Mail Code L224, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239-3098, USA
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Clark SA, Davulcu O, Chapman MS. Crystal structures of arginine kinase in complex with ADP, nitrate, and various phosphagen analogs. Biochem Biophys Res Commun 2012; 427:212-7. [PMID: 22995310 DOI: 10.1016/j.bbrc.2012.09.053] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Accepted: 09/09/2012] [Indexed: 11/29/2022]
Abstract
Arginine kinase catalyzes the reversible transfer of a phosphoryl group between ATP and l-arginine and is a monomeric homolog of the human enzyme creatine kinase. Arginine and creatine kinases belongs to the phosphagen kinase family of enzymes, which consists of eight known members, each of which is specific for its own phosphagen. Here, the source of phosphagen specificity in arginine kinase is investigated through the use of phosphagen analogs. Crystal structures have been determined for Limulus polyphemus arginine kinase with one of four arginine analogs bound in a transition state analog complex: l-ornithine, l-citrulline, imino-l-ornithine, and d-arginine. In all complexes, the enzyme achieves a closed conformation very similar to that of the cognate transition state analog complex, but differences are observed in the configurations of bound ligands. Arginine kinase exhibits no detectable activity towards ornithine, citrulline, or imino-l-ornithine, and only trace activity towards d-arginine. The crystal structures presented here demonstrate that phosphagen specificity is derived neither from a lock-and-key mechanism nor a modulation of induced-fit conformational changes, but potentially from subtle distortions in bound substrate configurations.
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Affiliation(s)
- Shawn A Clark
- Institute of Molecular Biophysics, Department of Chemistry & Biochemistry, Florida State University, Tallahassee, FL 32306-4380, USA
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Rivière G, Hologne M, Marcillat O, Lancelin JM. Dynamical properties of the loop 320s of substrate-free and substrate-bound muscle creatine kinase by NMR: evidence for independent subunits. FEBS J 2012; 279:2863-75. [PMID: 22715856 DOI: 10.1111/j.1742-4658.2012.08667.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Muscle creatine kinase (MCK; EC2.7.3.2) is a 86 kDa homodimer that belongs to the family of guanidino kinases. MCK has been intensively studied for several decades, but it is still not known why it is a dimer because this quaternary structure does not translate into obvious structural or functional advantages over the homologous monomeric arginine kinase. In particular, it remains to be demonstrated whether MCK subunits are independent. Here, we describe NMR chemical-shift perturbation and relaxation experiments designed to study the active site 320s flexible loop of this enzyme. The analysis was performed with the enzyme in its ligand-free and MgADP-complexed forms, as well as with the transition-state analogue abortive complex (MCK-Mg-ADP-creatine-nitrate ion). Our data indicate that each subunit can bind substrates independently.
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Affiliation(s)
- Gwladys Rivière
- Institut des Sciences Analytiques, Université de Lyon, Université Claude Bernard Lyon 1, Villeurbanne, France
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