1
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Viviani LG, Kokh DB, Wade RC, T-do Amaral A. Molecular Dynamics Simulations of the Human Ecto-5'-Nucleotidase (h-ecto-5'-NT, CD73): Insights into Protein Flexibility and Binding Site Dynamics. J Chem Inf Model 2023; 63:4691-4707. [PMID: 37532679 DOI: 10.1021/acs.jcim.3c01068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/04/2023]
Abstract
Human ecto-5'-nucleotidase (h-ecto-5'-NT, CD73) is a homodimeric Zn2+-binding metallophosphoesterase that hydrolyzes adenosine 5'-monophosphate (5'-AMP) to adenosine and phosphate. h-Ecto-5'-NT is a key enzyme in purinergic signaling pathways and has been recognized as a promising biological target for several diseases, including cancer and inflammatory, infectious, and autoimmune diseases. Despite its importance as a biological target, little is known about h-ecto-5'-NT dynamics, which poses a considerable challenge to the design of inhibitors of this target enzyme. Here, to explore h-ecto-5'-NT flexibility, all-atom unbiased molecular dynamics (MD) simulations were performed. Remarkable differences in the dynamics of the open (catalytically inactive) and closed (catalytically active) conformations of the apo-h-ecto-5'-NT were observed during the simulations, and the nucleotide analogue inhibitor AMPCP was shown to stabilize the protein structure in the closed conformation. Our results suggest that the large and complex domain motion that enables the h-ecto-5'-NT open/closed conformational switch is slow, and therefore, it could not be completely captured within the time scale of our simulations. Nonetheless, we were able to explore the faster dynamics of the h-ecto-5'-NT substrate binding site, which is mainly located at the C-terminal domain and well conserved among the protein's open and closed conformations. Using the TRAPP ("Transient Pockets in Proteins") approach, we identified transient subpockets close to the substrate binding site. Finally, conformational states of the substrate binding site with higher druggability scores than the crystal structure were identified. In summary, our study provides valuable insights into h-ecto-5'-NT structural flexibility, which can guide the structure-based design of novel h-ecto-5'-NT inhibitors.
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Affiliation(s)
- Lucas G Viviani
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, Brazil
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, Brazil
| | - Daria B Kokh
- Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical Studies (HITS), 69118 Heidelberg, Germany
| | - Rebecca C Wade
- Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical Studies (HITS), 69118 Heidelberg, Germany
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany
- Interdisciplinary Center for Scientific Computing (IWR), Heidelberg University, 69120 Heidelberg, Germany
| | - Antonia T-do Amaral
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, Brazil
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2
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Tessmer MH, Stoll S. A novel approach to modeling side chain ensembles of the bifunctional spin label RX. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.24.542139. [PMID: 37292623 PMCID: PMC10245940 DOI: 10.1101/2023.05.24.542139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We introduce a novel approach to modeling side chain ensembles of bifunctional spin labels. This approach utilizes rotamer libraries to generate side chain conformational ensembles. Because the bifunctional label is constrained by two attachment sites, the label is split into two monofunctional rotamers which are first attached to their respective sites, then rejoined by a local optimization in dihedral space. We validate this method against a set of previously published experimental data using the bifunctional spin label, RX. This method is relatively fast and can readily be used for both experimental analysis and protein modeling, providing significant advantages over modeling bifunctional labels with molecular dynamics simulations. Use of bifunctional labels for site directed spin labeling (SDSL) electron paramagnetic resonance (EPR) spectroscopy dramatically reduces label mobility, which can significantly improve resolution of small changes in protein backbone structure and dynamics. Coupling the use of bifunctional labels with side chain modeling methods allows for improved quantitative application of experimental SDSL EPR data to protein modeling.
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Affiliation(s)
- Maxx H. Tessmer
- Department of Chemistry, University of Washington, Seattle, WA 98103, United States
| | - Stefan Stoll
- Department of Chemistry, University of Washington, Seattle, WA 98103, United States
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3
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Schiemann O, Heubach CA, Abdullin D, Ackermann K, Azarkh M, Bagryanskaya EG, Drescher M, Endeward B, Freed JH, Galazzo L, Goldfarb D, Hett T, Esteban Hofer L, Fábregas Ibáñez L, Hustedt EJ, Kucher S, Kuprov I, Lovett JE, Meyer A, Ruthstein S, Saxena S, Stoll S, Timmel CR, Di Valentin M, Mchaourab HS, Prisner TF, Bode BE, Bordignon E, Bennati M, Jeschke G. Benchmark Test and Guidelines for DEER/PELDOR Experiments on Nitroxide-Labeled Biomolecules. J Am Chem Soc 2021; 143:17875-17890. [PMID: 34664948 DOI: 10.1021/jacs.1c07371] [Citation(s) in RCA: 105] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Distance distribution information obtained by pulsed dipolar EPR spectroscopy provides an important contribution to many studies in structural biology. Increasingly, such information is used in integrative structural modeling, where it delivers unique restraints on the width of conformational ensembles. In order to ensure reliability of the structural models and of biological conclusions, we herein define quality standards for sample preparation and characterization, for measurements of distributed dipole-dipole couplings between paramagnetic labels, for conversion of the primary time-domain data into distance distributions, for interpreting these distributions, and for reporting results. These guidelines are substantiated by a multi-laboratory benchmark study and by analysis of data sets with known distance distribution ground truth. The study and the guidelines focus on proteins labeled with nitroxides and on double electron-electron resonance (DEER aka PELDOR) measurements and provide suggestions on how to proceed analogously in other cases.
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Affiliation(s)
- Olav Schiemann
- Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstraße 12, 53115 Bonn, Germany
| | - Caspar A Heubach
- Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstraße 12, 53115 Bonn, Germany
| | - Dinar Abdullin
- Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstraße 12, 53115 Bonn, Germany
| | - Katrin Ackermann
- EaStCHEM School of Chemistry, Biomedical Sciences Research Complex, and Centre of Magnetic Resonance, University of St Andrews North Haugh, St Andrews KY16 9ST, U.K
| | - Mykhailo Azarkh
- Department of Chemistry and Konstanz Research School Chemical Biology, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
| | - Elena G Bagryanskaya
- N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Lavrentieva aven 9, 630090 Novosibirsk, Russia
| | - Malte Drescher
- Department of Chemistry and Konstanz Research School Chemical Biology, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
| | - Burkhard Endeward
- Institute of Physical and Theoretical Chemistry and Center of Biomolecular Magnetic Resonance, Goethe University, 60438 Frankfurt am Main, Germany
| | - Jack H Freed
- Department of Chemistry and Chemical Biology, and ACERT, National Biomedical Center for Advanced Electron Spin Resonance Technology, Cornell University, Ithaca, New York 14853-1301, United States
| | - Laura Galazzo
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, 44801 Bochum, Germany
| | - Daniella Goldfarb
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Tobias Hett
- Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstraße 12, 53115 Bonn, Germany
| | - Laura Esteban Hofer
- Department of Chemistry and Applied Biosciences, ETH Hönggerberg, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Luis Fábregas Ibáñez
- Department of Chemistry and Applied Biosciences, ETH Hönggerberg, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Eric J Hustedt
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Svetlana Kucher
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, 44801 Bochum, Germany
| | - Ilya Kuprov
- School of Chemistry, University of Southampton, Highfield Campus, Southampton SO17 1BJ, U.K
| | - Janet Eleanor Lovett
- SUPA School of Physics and Astronomy and BSRC, University of St Andrews, North Haugh, St Andrews KY16 9SS, U.K
| | - Andreas Meyer
- Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Sharon Ruthstein
- Department of Chemistry, Bar Ilan University, Ramat Gan 5290002, Israel
| | - Sunil Saxena
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Stefan Stoll
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Christiane R Timmel
- Department of Chemistry, Centre for Advanced Electron Spin Resonance, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K
| | - Marilena Di Valentin
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
| | - Hassane S Mchaourab
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Thomas F Prisner
- Institute of Physical and Theoretical Chemistry and Center of Biomolecular Magnetic Resonance, Goethe University, 60438 Frankfurt am Main, Germany
| | - Bela Ernest Bode
- EaStCHEM School of Chemistry, Biomedical Sciences Research Complex, and Centre of Magnetic Resonance, University of St Andrews North Haugh, St Andrews KY16 9ST, U.K
| | - Enrica Bordignon
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, 44801 Bochum, Germany
| | - Marina Bennati
- Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Gunnar Jeschke
- Department of Chemistry and Applied Biosciences, ETH Hönggerberg, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
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4
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Born A, Soetbeer J, Breitgoff F, Henen MA, Sgourakis N, Polyhach Y, Nichols PJ, Strotz D, Jeschke G, Vögeli B. Reconstruction of Coupled Intra- and Interdomain Protein Motion from Nuclear and Electron Magnetic Resonance. J Am Chem Soc 2021; 143:16055-16067. [PMID: 34579531 DOI: 10.1021/jacs.1c06289] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Proteins composed of multiple domains allow for structural heterogeneity and interdomain dynamics that may be vital for function. Intradomain structures and dynamics can influence interdomain conformations and vice versa. However, no established structure determination method is currently available that can probe the coupling of these motions. The protein Pin1 contains separate regulatory and catalytic domains that sample "extended" and "compact" states, and ligand binding changes this equilibrium. Ligand binding and interdomain distance have been shown to impact the activity of Pin1, suggesting interdomain allostery. In order to characterize the conformational equilibrium of Pin1, we describe a novel method to model the coupling between intra- and interdomain dynamics at atomic resolution using multistate ensembles. The method uses time-averaged nuclear magnetic resonance (NMR) restraints and double electron-electron resonance (DEER) data that resolve distance distributions. While the intradomain calculation is primarily driven by exact nuclear Overhauser enhancements (eNOEs), J couplings, and residual dipolar couplings (RDCs), the relative domain distribution is driven by paramagnetic relaxation enhancement (PREs), RDCs, interdomain NOEs, and DEER. Our data support a 70:30 population of the compact and extended states in apo Pin1. A multistate ensemble describes these conformations simultaneously, with distinct conformational differences located in the interdomain interface stabilizing the compact or extended states. We also describe correlated conformations between the catalytic site and interdomain interface that may explain allostery driven by interdomain contact.
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Affiliation(s)
- Alexandra Born
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, 12801 East 17th Avenue, Aurora, Colorado 80045, United States
| | - Janne Soetbeer
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, ETH-Hönggerberg, Zürich CH-8093, Switzerland
| | - Frauke Breitgoff
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, ETH-Hönggerberg, Zürich CH-8093, Switzerland
| | - Morkos A Henen
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, 12801 East 17th Avenue, Aurora, Colorado 80045, United States.,Faculty of Pharmacy, Mansoura University, Mansoura 35516, Egypt
| | - Nikolaos Sgourakis
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Yevhen Polyhach
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, ETH-Hönggerberg, Zürich CH-8093, Switzerland
| | - Parker J Nichols
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, 12801 East 17th Avenue, Aurora, Colorado 80045, United States
| | - Dean Strotz
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, ETH-Hönggerberg, Zürich CH-8093, Switzerland
| | - Gunnar Jeschke
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, ETH-Hönggerberg, Zürich CH-8093, Switzerland
| | - Beat Vögeli
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, 12801 East 17th Avenue, Aurora, Colorado 80045, United States
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5
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Scaletti E, Huschmann FU, Mueller U, Weiss MS, Sträter N. Substrate binding modes of purine and pyrimidine nucleotides to human ecto-5'-nucleotidase (CD73) and inhibition by their bisphosphonic acid derivatives. Purinergic Signal 2021; 17:693-704. [PMID: 34403084 PMCID: PMC8677862 DOI: 10.1007/s11302-021-09802-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Accepted: 06/07/2021] [Indexed: 12/20/2022] Open
Abstract
Human ecto-5-nucleotidase (CD73) is involved in purinergic signalling, which influences a diverse range of biological processes. CD73 hydrolyses AMP and is the major control point for the levels of extracellular adenosine. Inhibitors of CD73 thus block the immunosuppressive action of adenosine, a promising approach for cancer immunotherapy. Interestingly, ADP and ATP are competitive inhibitors of CD73, with the most potent small-molecule inhibitors to date being non-hydrolysable ADP analogues. While AMP is the major substrate of the enzyme, CD73 has been reported to hydrolyse other 5′-nucleoside monophosphates. Based on a fragment screening campaign at the BESSY II synchrotron, we present the binding modes of various deoxyribo- and ribonucleoside monophosphates and of four additional fragments binding to the nucleoside binding site of the open form of the enzyme. Kinetic analysis of monophosphate hydrolysis shows that ribonucleotide substrates are favoured over their deoxyribose equivalents with AMP being the best substrate. We characterised the initial step of AMP hydrolysis, the binding mode of AMP to the open conformation of CD73 and compared that to other monophosphate substrates. In addition, the inhibitory activity of various bisphosphonic acid derivatives of nucleoside diphosphates was determined. Although AMPCP remains the most potent inhibitor, replacement of the adenine base with other purines or with pyrimidines increases the Ki value only between twofold and sixfold. On the other hand, these nucleobases offer new opportunities to attach substituents for improved pharmacological properties.
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Affiliation(s)
- Emma Scaletti
- Institute of Bioanalytical Chemistry, Centre for Biotechnology and Biomedicine, Leipzig University, Deutscher Platz 5, 04103, Leipzig, Germany
| | - Franziska U Huschmann
- Helmholtz-Zentrum Berlin Für Materialien Und Energie, BESSY II, Albert-Einstein-Straße 15, 12489, Berlin, Germany
| | - Uwe Mueller
- Helmholtz-Zentrum Berlin Für Materialien Und Energie, BESSY II, Albert-Einstein-Straße 15, 12489, Berlin, Germany
| | - Manfred S Weiss
- Helmholtz-Zentrum Berlin Für Materialien Und Energie, BESSY II, Albert-Einstein-Straße 15, 12489, Berlin, Germany
| | - Norbert Sträter
- Institute of Bioanalytical Chemistry, Centre for Biotechnology and Biomedicine, Leipzig University, Deutscher Platz 5, 04103, Leipzig, Germany.
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6
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del Alamo D, Jagessar KL, Meiler J, Mchaourab HS. Methodology for rigorous modeling of protein conformational changes by Rosetta using DEER distance restraints. PLoS Comput Biol 2021; 17:e1009107. [PMID: 34133419 PMCID: PMC8238229 DOI: 10.1371/journal.pcbi.1009107] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Revised: 06/28/2021] [Accepted: 05/24/2021] [Indexed: 12/20/2022] Open
Abstract
We describe an approach for integrating distance restraints from Double Electron-Electron Resonance (DEER) spectroscopy into Rosetta with the purpose of modeling alternative protein conformations from an initial experimental structure. Fundamental to this approach is a multilateration algorithm that harnesses sets of interconnected spin label pairs to identify optimal rotamer ensembles at each residue that fit the DEER decay in the time domain. Benchmarked relative to data analysis packages, the algorithm yields comparable distance distributions with the advantage that fitting the DEER decay and rotamer ensemble optimization are coupled. We demonstrate this approach by modeling the protonation-dependent transition of the multidrug transporter PfMATE to an inward facing conformation with a deviation to the experimental structure of less than 2Å Cα RMSD. By decreasing spin label rotamer entropy, this approach engenders more accurate Rosetta models that are also more closely clustered, thus setting the stage for more robust modeling of protein conformational changes.
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Affiliation(s)
- Diego del Alamo
- Department of Chemistry and Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, United States of America
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Kevin L. Jagessar
- Department of Chemistry and Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, United States of America
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Jens Meiler
- Department of Chemistry and Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, United States of America
- Institute for Drug Discovery, Leipzig University Medical School, Leipzig, Germany
| | - Hassane S. Mchaourab
- Department of Chemistry and Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, United States of America
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States of America
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7
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Cabezas A, López-Villamizar I, Costas MJ, Cameselle JC, Ribeiro JM. Substrate Specificity of Chimeric Enzymes Formed by Interchange of the Catalytic and Specificity Domains of the 5 '-Nucleotidase UshA and the 3 '-Nucleotidase CpdB. Molecules 2021; 26:molecules26082307. [PMID: 33923386 PMCID: PMC8071527 DOI: 10.3390/molecules26082307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 03/31/2021] [Accepted: 04/13/2021] [Indexed: 11/16/2022] Open
Abstract
The 5′-nucleotidase UshA and the 3′-nucleotidase CpdB from Escherichia coli are broad-specificity phosphohydrolases with similar two-domain structures. Their N-terminal domains (UshA_Ndom and CpdB_Ndom) contain the catalytic site, and their C-terminal domains (UshA_Cdom and CpdB_Cdom) contain a substrate-binding site responsible for specificity. Both enzymes show only partial overlap in their substrate specificities. So, it was decided to investigate the catalytic behavior of chimeras bearing the UshA catalytic domain and the CpdB specificity domain, or vice versa. UshA_Ndom–CpdB_Cdom and CpdB_Ndom–UshA_Cdom were constructed and tested on substrates specific to UshA (5′-AMP, CDP-choline, UDP-glucose) or to CpdB (3′-AMP), as well as on 2′,3′-cAMP and on the common phosphodiester substrate bis-4-NPP (bis-4-nitrophenylphosphate). The chimeras did show neither 5′-nucleotidase nor 3′-nucleotidase activity. When compared to UshA, UshA_Ndom–CpdB_Cdom conserved high activity on bis-4-NPP, some on CDP-choline and UDP-glucose, and displayed activity on 2′,3′-cAMP. When compared to CpdB, CpdB_Ndom–UshA_Cdom conserved phosphodiesterase activities on 2′,3′-cAMP and bis-4-NPP, and gained activity on the phosphoanhydride CDP-choline. Therefore, the non-nucleotidase activities of UshA and CpdB are not fully dependent on the interplay between domains. The specificity domains may confer the chimeras some of the phosphodiester or phosphoanhydride selectivity displayed when associated with their native partners. Contrarily, the nucleotidase activity of UshA and CpdB depends strictly on the interplay between their native catalytic and specificity domains.
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Affiliation(s)
- Alicia Cabezas
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina y Ciencias de la Salud, Universidad de Extremadura, 06006 Badajoz, Spain; (A.C.); (I.L.-V.); (M.J.C.); (J.C.C.)
| | - Iralis López-Villamizar
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina y Ciencias de la Salud, Universidad de Extremadura, 06006 Badajoz, Spain; (A.C.); (I.L.-V.); (M.J.C.); (J.C.C.)
- Manlab, Diagnóstico Bioquímico y Genómico, Calle Marcelo Torcuato de Alvear 2263, 1122 Ciudad de Buenos Aires, Argentina
| | - María Jesús Costas
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina y Ciencias de la Salud, Universidad de Extremadura, 06006 Badajoz, Spain; (A.C.); (I.L.-V.); (M.J.C.); (J.C.C.)
| | - José Carlos Cameselle
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina y Ciencias de la Salud, Universidad de Extremadura, 06006 Badajoz, Spain; (A.C.); (I.L.-V.); (M.J.C.); (J.C.C.)
| | - João Meireles Ribeiro
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina y Ciencias de la Salud, Universidad de Extremadura, 06006 Badajoz, Spain; (A.C.); (I.L.-V.); (M.J.C.); (J.C.C.)
- Correspondence:
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8
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Hays JM, Boland E, Kasson PM. Inference of Joint Conformational Distributions from Separately Acquired Experimental Measurements. J Phys Chem Lett 2021; 12:1606-1611. [PMID: 33596657 PMCID: PMC8310705 DOI: 10.1021/acs.jpclett.0c03623] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Flexible proteins serve vital roles in a multitude of biological processes. However, determining their full conformational ensembles is extremely difficult because this requires detailed knowledge about the heterogeneity of the protein's degrees of freedom. Label-based experiments such as double electron-electron resonance (DEER) are very useful in studying flexible proteins, as they provide distributional data on heterogeneity. These experiments are typically performed separately, so information about correlation between distributions is lost. We have developed a method to recover correlation information using nonequilibrium work estimates in molecular dynamics refinement. We tested this method on a simple model of an alternating-access transporter for which the true joint distributions are known, and it successfully recovered the true joint distribution. We also applied our method to the protein syntaxin-1a, where it discarded physically implausible conformations. Our method thus provides a way to recover correlation structure in separate experimental measurements of conformational ensembles and refines the resulting structural ensemble.
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Affiliation(s)
- Jennifer M. Hays
- Department of Biomedical Engineering, University of Virginia, Charlottesville, VA, USA
- Department of Molecular Physiology, University of Virginia, Charlottesville, VA, USA
| | - Emily Boland
- Department of Biomedical Engineering, University of Virginia, Charlottesville, VA, USA
- Department of Molecular Physiology, University of Virginia, Charlottesville, VA, USA
| | - Peter M. Kasson
- Department of Biomedical Engineering, University of Virginia, Charlottesville, VA, USA
- Department of Molecular Physiology, University of Virginia, Charlottesville, VA, USA
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala, 75124 Sweden
- Corresponding Author:
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9
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López-Villamizar I, Cabezas A, Pinto RM, Canales J, Ribeiro JM, Rodrigues JR, Costas MJ, Cameselle JC. Molecular Dissection of Escherichia coli CpdB: Roles of the N Domain in Catalysis and Phosphate Inhibition, and of the C Domain in Substrate Specificity and Adenosine Inhibition. Int J Mol Sci 2021; 22:ijms22041977. [PMID: 33671286 PMCID: PMC7922932 DOI: 10.3390/ijms22041977] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 02/09/2021] [Accepted: 02/15/2021] [Indexed: 12/17/2022] Open
Abstract
CpdB is a 3′-nucleotidase/2′3′-cyclic nucleotide phosphodiesterase, active also with reasonable efficiency on cyclic dinucleotides like c-di-AMP (3′,5′-cyclic diadenosine monophosphate) and c-di-GMP (3′,5′-cyclic diadenosine monophosphate). These are regulators of bacterial physiology, but are also pathogen-associated molecular patterns recognized by STING to induce IFN-β response in infected hosts. The cpdB gene of Gram-negative and its homologs of gram-positive bacteria are virulence factors. Their protein products are extracytoplasmic enzymes (either periplasmic or cell–wall anchored) and can hydrolyze extracellular cyclic dinucleotides, thus reducing the innate immune responses of infected hosts. This makes CpdB(-like) enzymes potential targets for novel therapeutic strategies in infectious diseases, bringing about the necessity to gain insight into the molecular bases of their catalytic behavior. We have dissected the two-domain structure of Escherichia coli CpdB to study the role of its N-terminal and C-terminal domains (CpdB_Ndom and CpdB_Cdom). The specificity, kinetics and inhibitor sensitivity of point mutants of CpdB, and truncated proteins CpdB_Ndom and CpdB_Cdom were investigated. CpdB_Ndom contains the catalytic site, is inhibited by phosphate but not by adenosine, while CpdB_Cdom is inactive but contains a substrate-binding site that determines substrate specificity and adenosine inhibition of CpdB. Among CpdB substrates, 3′-AMP, cyclic dinucleotides and linear dinucleotides are strongly dependent on the CpdB_Cdom binding site for activity, as the isolated CpdB_Ndom showed much-diminished activity on them. In contrast, 2′,3′-cyclic mononucleotides and bis-4-nitrophenylphosphate were actively hydrolyzed by CpdB_Ndom, indicating that they are rather independent of the CpdB_Cdom binding site.
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Affiliation(s)
- Iralis López-Villamizar
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, 06006 Badajoz, Spain; (I.L.-V.); (A.C.); (R.M.P.); (J.C.); (J.M.R.); (M.J.C.)
| | - Alicia Cabezas
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, 06006 Badajoz, Spain; (I.L.-V.); (A.C.); (R.M.P.); (J.C.); (J.M.R.); (M.J.C.)
| | - Rosa María Pinto
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, 06006 Badajoz, Spain; (I.L.-V.); (A.C.); (R.M.P.); (J.C.); (J.M.R.); (M.J.C.)
| | - José Canales
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, 06006 Badajoz, Spain; (I.L.-V.); (A.C.); (R.M.P.); (J.C.); (J.M.R.); (M.J.C.)
| | - João Meireles Ribeiro
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, 06006 Badajoz, Spain; (I.L.-V.); (A.C.); (R.M.P.); (J.C.); (J.M.R.); (M.J.C.)
| | - Joaquim Rui Rodrigues
- Laboratório Associado LSRE-LCM, Escola Superior de Tecnologia e Gestão, Instituto Politécnico de Leiria, 2411-901 Leiria, Portugal;
| | - María Jesús Costas
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, 06006 Badajoz, Spain; (I.L.-V.); (A.C.); (R.M.P.); (J.C.); (J.M.R.); (M.J.C.)
| | - José Carlos Cameselle
- Grupo de Enzimología, Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Medicina, Universidad de Extremadura, 06006 Badajoz, Spain; (I.L.-V.); (A.C.); (R.M.P.); (J.C.); (J.M.R.); (M.J.C.)
- Correspondence: ; Tel.: +34-924-289-470
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10
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Xie E, Su Y, Deng S, Kontopyrgou M, Zhang D. Significant influence of phosphorus resources on the growth and alkaline phosphatase activities of Microcystis aeruginosa. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 268:115807. [PMID: 33096390 DOI: 10.1016/j.envpol.2020.115807] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 10/01/2020] [Accepted: 10/09/2020] [Indexed: 06/11/2023]
Abstract
It is well-accepted that phosphorus, particularly orthophosphate, is a determinant factor in aquatic eutrophication. However, numerous kinds of phosphorus sources exist in real world scenario, and limited studies have characterized the pairwise relationships among abundant different phosphorus sources and the physiological behaviour of algae. The present study developed a high-throughput assay to investigate the effects of 59 different phosphorus sources (equal initial concentration of total phosphorus) on the growth and alkaline phosphatase (AKP) activities of Microcystis aeruginosa, a model cyanobacteria whose predominance holds sway in lake eutrophication. M. aeruginosa cultivated with nucleoside monophosphates (NMPs) had higher growth, relative AKP activities and residual orthophosphate, which were positively intercorrelated. Oppositely, non-NMPs cultivation of M. aeruginosa led to negative relationships between the relative AKP activities and their growth or residual orthophosphate. These results indicated distinct mechanisms for M. aeruginosa to utilize different phosphorus sources in real-world scenario, and both phosphorus source and content are determinant factors on the growth and physiological behaviour of M. aeruginosa. Given the complicated and vast phosphorus pool in the natural environment, phosphorus resources might significantly alter the abundance and physiological behaviour of M. aeruginosa and other bloom-forming algae, then influence the phytoplanktonic community structure and affect the possibility and intensity of algal bloom. Our work hints the underestimation of the restriction factors in lake eutrophication and provides a new tool to study the driven forces of phytoplanktonic community dynamics as phosphorus from both internal and external sources.
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Affiliation(s)
- En Xie
- College of Water Resources and Civil Engineering, China Agricultural University, Beijing, 100083, China
| | - Yuping Su
- Environmental Science and Engineering College, Fujian Normal University, Fuzhou, 350007, PR China
| | - Songqiang Deng
- Research Institute for Environmental Innovation (Suzhou), Tsinghua, Suzhou, 215163, PR China
| | - Maria Kontopyrgou
- Lancaster Environment Centre, Lancaster University, Lancaster, LA1 2YW, United Kingdom
| | - Dayi Zhang
- School of Environment, Tsinghua University, Beijing, 100084, PR China.
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11
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Del Alamo D, Tessmer MH, Stein RA, Feix JB, Mchaourab HS, Meiler J. Rapid Simulation of Unprocessed DEER Decay Data for Protein Fold Prediction. Biophys J 2020; 118:366-375. [PMID: 31892409 PMCID: PMC6976798 DOI: 10.1016/j.bpj.2019.12.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 11/13/2019] [Accepted: 12/04/2019] [Indexed: 01/02/2023] Open
Abstract
Despite advances in sampling and scoring strategies, Monte Carlo modeling methods still struggle to accurately predict de novo the structures of large proteins, membrane proteins, or proteins of complex topologies. Previous approaches have addressed these shortcomings by leveraging sparse distance data gathered using site-directed spin labeling and electron paramagnetic resonance spectroscopy to improve protein structure prediction and refinement outcomes. However, existing computational implementations entail compromises between coarse-grained models of the spin label that lower the resolution and explicit models that lead to resource-intense simulations. These methods are further limited by their reliance on distance distributions, which are calculated from a primary refocused echo decay signal and contain uncertainties that may require manual refinement. Here, we addressed these challenges by developing RosettaDEER, a scoring method within the Rosetta software suite capable of simulating double electron-electron resonance spectroscopy decay traces and distance distributions between spin labels fast enough to fold proteins de novo. We demonstrate that the accuracy of resulting distance distributions match or exceed those generated by more computationally intensive methods. Moreover, decay traces generated from these distributions recapitulate intermolecular background coupling parameters even when the time window of data collection is truncated. As a result, RosettaDEER can discriminate between poorly folded and native-like models by using decay traces that cannot be accurately converted into distance distributions using regularized fitting approaches. Finally, using two challenging test cases, we demonstrate that RosettaDEER leverages these experimental data for protein fold prediction more effectively than previous methods. These benchmarking results confirm that RosettaDEER can effectively leverage sparse experimental data for a wide array of modeling applications built into the Rosetta software suite.
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Affiliation(s)
- Diego Del Alamo
- Department of Chemistry and Center for Structural Biology; Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | | | - Richard A Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Jimmy B Feix
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Hassane S Mchaourab
- Department of Chemistry and Center for Structural Biology; Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Jens Meiler
- Department of Chemistry and Center for Structural Biology; Institut for Drug Discovery, Leipzig University, Leipzig, Germany.
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12
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Zheng L, Ren M, Xie E, Ding A, Liu Y, Deng S, Zhang D. Roles of Phosphorus Sources in Microbial Community Assembly for the Removal of Organic Matters and Ammonia in Activated Sludge. Front Microbiol 2019; 10:1023. [PMID: 31156575 PMCID: PMC6532738 DOI: 10.3389/fmicb.2019.01023] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2019] [Accepted: 04/24/2019] [Indexed: 11/13/2022] Open
Abstract
Various phosphorus sources are utilized by microbes in WWTPs, eventually affecting microbial assembly and functions. This study identified the effects of phosphorus source on microbial communities and functions in the activated sludge. By cultivation with 59 phosphorus sources, including inorganic phosphates (IP), nucleoside-monophosphates (NMP), cyclic-nucleoside-monophosphates (cNMP), and other organophosphates (OP), we evaluated the change in removal efficiencies of total organic carbon (TOC) and ammonia, microbial biomass, alkaline phosphatase (AKP) activity, microbial community structure, and AKP-associated genes. TOC and ammonia removal efficiency was highest in IP (64.8%) and cNMP (52.3%) treatments. Microbial community structure changed significantly across phosphorus sources that IP and cNMP encouraged Enterobacter and Aeromonas, respectively. The abundance of phoA and phoU genes was higher in IP treatments, whereas phoD and phoX genes dominated OP treatments. Our findings suggested that the performance of WWTPs was dependent on phosphorus sources and provided new insights into effective WWTP management.
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Affiliation(s)
- Lei Zheng
- College of Water Science, Beijing Normal University, Beijing, China
| | - Mengli Ren
- College of Water Science, Beijing Normal University, Beijing, China
| | - En Xie
- College of Water Resources and Civil Engineering, China Agricultural University, Beijing, China
| | - Aizhong Ding
- College of Water Science, Beijing Normal University, Beijing, China
| | - Yan Liu
- Chinese Research Academy of Environmental Sciences, Beijing, China
| | - Songqiang Deng
- Research Institute for Environmental Innovation (Tsinghua-Suzhou), Suzhou, China
| | - Dayi Zhang
- School of Environment, Tsinghua University, Beijing, China
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13
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Bryant JM, Blind RD. Signaling through non-membrane nuclear phosphoinositide binding proteins in human health and disease. J Lipid Res 2018; 60:299-311. [PMID: 30201631 DOI: 10.1194/jlr.r088518] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 08/22/2018] [Indexed: 12/22/2022] Open
Abstract
Phosphoinositide membrane signaling is critical for normal physiology, playing well-known roles in diverse human pathologies. The basic mechanisms governing phosphoinositide signaling within the nucleus, however, have remained deeply enigmatic owing to their presence outside the nuclear membranes. Over 40% of nuclear phosphoinositides can exist in this non-membrane state, held soluble in the nucleoplasm by nuclear proteins that remain largely unidentified. Recently, two nuclear proteins responsible for solubilizing phosphoinositides were identified, steroidogenic factor-1 (SF-1; NR5A1) and liver receptor homolog-1 (LRH-1; NR5A2), along with two enzymes that directly remodel these phosphoinositide/protein complexes, phosphatase and tensin homolog (PTEN; MMAC) and inositol polyphosphate multikinase (IPMK; ipk2). These new footholds now permit the assignment of physiological functions for nuclear phosphoinositides in human diseases, such as endometriosis, nonalcoholic fatty liver disease/steatohepatitis, glioblastoma, and hepatocellular carcinoma. The unique nature of nuclear phosphoinositide signaling affords extraordinary clinical opportunities for new biomarkers, diagnostics, and therapeutics. Thus, phosphoinositide biology within the nucleus may represent the next generation of low-hanging fruit for new drugs, not unlike what has occurred for membrane phosphatidylinositol 3-kinase drug development. This review connects recent basic science discoveries in nuclear phosphoinositide signaling to clinical pathologies, with the hope of inspiring development of new therapies.
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Affiliation(s)
- Jamal M Bryant
- Departments of Pharmacology, Biochemistry, and Medicine, Division of Diabetes, Endocrinology, and Metabolism, Vanderbilt Diabetes Research and Training Center, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Raymond D Blind
- Departments of Pharmacology, Biochemistry, and Medicine, Division of Diabetes, Endocrinology, and Metabolism, Vanderbilt Diabetes Research and Training Center, Vanderbilt University School of Medicine, Nashville, TN 37232
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14
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Abstract
Biological macromolecules often undergo large conformational rearrangements during a functional cycle. To simulate these structural transitions with full atomic detail typically demands extensive computational resources. Moreover, it is unclear how to incorporate, in a principled way, additional experimental information that could guide the structural transition. This article develops a probabilistic model for conformational transitions in biomolecules. The model can be viewed as a network of anharmonic springs that break, if the experimental data support the rupture of bonds. Hamiltonian Monte Carlo in internal coordinates is used to infer structural transitions from experimental data, thereby sampling large conformational transitions without distorting the structure. The model is benchmarked on a large set of conformational transitions. Moreover, we demonstrate the use of the probabilistic network model for integrative modeling of macromolecular complexes based on data from crosslinking followed by mass spectrometry.
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Affiliation(s)
- Michael Habeck
- Statistical Inverse Problems in Biophysics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany.,Felix Bernstein Institute for Mathematical Statistics in the Biosciences, Georg August University Göttingen, Goldschmidtstrasse 7, 37077, Göttingen, Germany
| | - Thach Nguyen
- Felix Bernstein Institute for Mathematical Statistics in the Biosciences, Georg August University Göttingen, Goldschmidtstrasse 7, 37077, Göttingen, Germany
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15
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The contribution of modern EPR to structural biology. Emerg Top Life Sci 2018; 2:9-18. [PMID: 33525779 PMCID: PMC7288997 DOI: 10.1042/etls20170143] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 12/22/2017] [Accepted: 01/02/2018] [Indexed: 02/08/2023]
Abstract
Electron paramagnetic resonance (EPR) spectroscopy combined with site-directed spin labelling is applicable to biomolecules and their complexes irrespective of system size and in a broad range of environments. Neither short-range nor long-range order is required to obtain structural restraints on accessibility of sites to water or oxygen, on secondary structure, and on distances between sites. Many of the experiments characterize a static ensemble obtained by shock-freezing. Compared with characterizing the dynamic ensemble at ambient temperature, analysis is simplified and information loss due to overlapping timescales of measurement and system dynamics is avoided. The necessity for labelling leads to sparse restraint sets that require integration with data from other methodologies for building models. The double electron–electron resonance experiment provides distance distributions in the nanometre range that carry information not only on the mean conformation but also on the width of the native ensemble. The distribution widths are often inconsistent with Anfinsen's concept that a sequence encodes a single native conformation defined at atomic resolution under physiological conditions.
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16
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Carrington B, Myers WK, Horanyi P, Calmiano M, Lawson ADG. Natural Conformational Sampling of Human TNFα Visualized by Double Electron-Electron Resonance. Biophys J 2017; 113:371-380. [PMID: 28746848 PMCID: PMC5529296 DOI: 10.1016/j.bpj.2017.06.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 05/05/2017] [Accepted: 06/06/2017] [Indexed: 12/20/2022] Open
Abstract
Double electron-electron resonance in conjunction with site-directed spin labeling has been used to probe natural conformational sampling of the human tumor necrosis factor α trimer. We suggest a previously unreported, predeoligomerization conformation of the trimer that has been shown to be sampled at low frequency. A model of this trimeric state has been constructed based on crystal structures using the double-electron-electron-resonance distances. The model shows one of the protomers to be rotated and tilted outward at the tip end, leading to a breaking of the trimerous symmetry and distortion at a receptor-binding interface. The new structure offers opportunities to modulate the biological activity of tumor necrosis factor α through stabilization of the distorted trimer with small molecules.
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Affiliation(s)
| | - William K Myers
- Department of Inorganic Chemistry, University of Oxford, Oxford, United Kingdom
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17
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Lai AL, Clerico EM, Blackburn ME, Patel NA, Robinson CV, Borbat PP, Freed JH, Gierasch LM. Key features of an Hsp70 chaperone allosteric landscape revealed by ion-mobility native mass spectrometry and double electron-electron resonance. J Biol Chem 2017; 292:8773-8785. [PMID: 28428246 PMCID: PMC5448104 DOI: 10.1074/jbc.m116.770404] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 04/12/2017] [Indexed: 11/06/2022] Open
Abstract
Proteins are dynamic entities that populate conformational ensembles, and most functions of proteins depend on their dynamic character. Allostery, in particular, relies on ligand-modulated shifts in these conformational ensembles. Hsp70s are allosteric molecular chaperones with conformational landscapes that involve large rearrangements of their two domains (viz. the nucleotide-binding domain and substrate-binding domain) in response to adenine nucleotides and substrates. However, it remains unclear how the Hsp70 conformational ensemble is populated at each point of the allosteric cycle and how ligands control these populations. We have mapped the conformational species present under different ligand-binding conditions throughout the allosteric cycle of the Escherichia coli Hsp70 DnaK by two complementary methods, ion-mobility mass spectrometry and double electron-electron resonance. Our results obtained under biologically relevant ligand-bound conditions confirm the current picture derived from NMR and crystallographic data of domain docking upon ATP binding and undocking in response to ADP and substrate. Additionally, we find that the helical lid of DnaK is a highly dynamic unit of the structure in all ligand-bound states. Importantly, we demonstrate that DnaK populates a partially docked state in the presence of ATP and substrate and that this state represents an energy minimum on the DnaK allosteric landscape. Because Hsp70s are emerging as potential drug targets for many diseases, fully mapping an allosteric landscape of a molecular chaperone like DnaK will facilitate the development of small molecules that modulate Hsp70 function via allosteric mechanisms.
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Affiliation(s)
- Alex L Lai
- From the Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-2703
| | | | - Mandy E Blackburn
- the School of Environmental, Physical, and Applied Sciences, University of Central Missouri, Warrensburg, Missouri 64093, and
| | - Nisha A Patel
- the Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Carol V Robinson
- the Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Peter P Borbat
- From the Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-2703
| | - Jack H Freed
- From the Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-2703
| | - Lila M Gierasch
- the Departments of Biochemistry and Molecular Biology and .,Chemistry, University of Massachusetts, Amherst, Massachusetts 01003
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