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Hung CL, Chang HH, Lee SW, Chiang YW. Stepwise activation of the pro-apoptotic protein Bid at mitochondrial membranes. Cell Death Differ 2021; 28:1910-1925. [PMID: 33462413 PMCID: PMC8184993 DOI: 10.1038/s41418-020-00716-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 12/01/2020] [Accepted: 12/16/2020] [Indexed: 01/30/2023] Open
Abstract
Caspase-8-cleaved Bid (cBid) associates with mitochondria and promotes the activation of BAX, leading to mitochondria outer membrane permeabilization (MOMP) and apoptosis. However, current structural models of cBid are largely based on studies using membrane vesicles and detergent micelles. Here we employ spin-label ESR and site-directed PEGylation methods to identify conformations of cBid at real mitochondrial membranes, revealing stepwise mechanisms in the activation process. Upon the binding of cBid to mitochondria, its structure is reorganized to expose the BH3 domain while leaving the structural integrity only slightly altered. The mitochondria-bound cBid is in association with Mtch2 and it remains in the primed state until interacting with BAX. The interaction subsequently triggers the fragmentation of cBid, causes large conformational changes, and promotes BAX-mediated MOMP. Our results reveal structural differences of cBid between mitochondria and other lipid-like environments and, moreover, highlight the role of the membrane binding in modifying cBid structure and assisting the inactive-to-active transition in function.
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Affiliation(s)
- Chien-Lun Hung
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan
| | - Hsin-Ho Chang
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan
| | - Su Wei Lee
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan
| | - Yun-Wei Chiang
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan.
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2
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Reinknecht C, Riga A, Rivera J, Snyder DA. Patterns in Protein Flexibility: A Comparison of NMR "Ensembles", MD Trajectories, and Crystallographic B-Factors. Molecules 2021; 26:molecules26051484. [PMID: 33803249 PMCID: PMC7967184 DOI: 10.3390/molecules26051484] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 02/18/2021] [Accepted: 02/28/2021] [Indexed: 11/16/2022] Open
Abstract
Proteins are molecular machines requiring flexibility to function. Crystallographic B-factors and Molecular Dynamics (MD) simulations both provide insights into protein flexibility on an atomic scale. Nuclear Magnetic Resonance (NMR) lacks a universally accepted analog of the B-factor. However, a lack of convergence in atomic coordinates in an NMR-based structure calculation also suggests atomic mobility. This paper describes a pattern in the coordinate uncertainties of backbone heavy atoms in NMR-derived structural “ensembles” first noted in the development of FindCore2 (previously called Expanded FindCore: DA Snyder, J Grullon, YJ Huang, R Tejero, GT Montelione, Proteins: Structure, Function, and Bioinformatics 82 (S2), 219–230) and demonstrates that this pattern exists in coordinate variances across MD trajectories but not in crystallographic B-factors. This either suggests that MD trajectories and NMR “ensembles” capture motional behavior of peptide bond units not captured by B-factors or indicates a deficiency common to force fields used in both NMR and MD calculations.
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3
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Podlewska S, Bugno R, Lacivita E, Leopoldo M, Bojarski AJ, Handzlik J. Low Basicity as a Characteristic for Atypical Ligands of Serotonin Receptor 5-HT2. Int J Mol Sci 2021; 22:ijms22031035. [PMID: 33494248 PMCID: PMC7864501 DOI: 10.3390/ijms22031035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 01/15/2021] [Accepted: 01/16/2021] [Indexed: 02/07/2023] Open
Abstract
Serotonin receptors are extensively examined by academic and industrial researchers, due to their vital roles, which they play in the organism and constituting therefore important drug targets. Up to very recently, it was assumed that the basic nitrogen in compound structure is a necessary component to make it active within this receptor system. Such nitrogen interacts in its protonated form with the aspartic acid from the third transmembrane helix (D3x32) forming a hydrogen bond tightly fitting the ligand in the protein binding site. However, there are several recent studies that report strong serotonin receptor affinity also for compounds without a basic moiety in their structures. In the study, we carried out a comprehensive in silico analysis of the low-basicity phenomenon of the selected serotonin receptor ligands. We focused on the crystallized representatives of the proteins of 5-HT1B, 5-HT2A, 5-HT2B, and 5-HT2C receptors, and examined the problem both from the ligand- and structure-based perspectives. The study was performed for the native proteins, and for D3x32A mutants. The investigation resulted in the determination of nonstandard structural requirements for activity towards serotonin receptors, which can be used in the design of new nonbasic ligands.
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Affiliation(s)
- Sabina Podlewska
- Department of Technology and Biotechnology of Drugs, Faculty of Pharmacy, Jagiellonian University Medical College, 9 Medyczna Street, 30-688 Kraków, Poland
- Maj Institute of Pharmacology, Polish Academy of Sciences, 12 Smętna Street, 31-343 Kraków, Poland; (R.B.); (A.J.B.)
- Correspondence: (S.P.); (J.H.); Tel.: +48-12-66-23-301 (S.P.); +48-12-620-55-84 (J.H.)
| | - Ryszard Bugno
- Maj Institute of Pharmacology, Polish Academy of Sciences, 12 Smętna Street, 31-343 Kraków, Poland; (R.B.); (A.J.B.)
| | - Enza Lacivita
- Department of Pharmacy-Drug Sciences, University of Bari “Aldo Moro”, via E. Orabona 4, 70125 Bari, Italy; (E.L.); (M.L.)
| | - Marcello Leopoldo
- Department of Pharmacy-Drug Sciences, University of Bari “Aldo Moro”, via E. Orabona 4, 70125 Bari, Italy; (E.L.); (M.L.)
| | - Andrzej J. Bojarski
- Maj Institute of Pharmacology, Polish Academy of Sciences, 12 Smętna Street, 31-343 Kraków, Poland; (R.B.); (A.J.B.)
| | - Jadwiga Handzlik
- Department of Technology and Biotechnology of Drugs, Faculty of Pharmacy, Jagiellonian University Medical College, 9 Medyczna Street, 30-688 Kraków, Poland
- Correspondence: (S.P.); (J.H.); Tel.: +48-12-66-23-301 (S.P.); +48-12-620-55-84 (J.H.)
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4
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Structural insights into serotonin receptor ligands polypharmacology. Eur J Med Chem 2018; 151:797-814. [DOI: 10.1016/j.ejmech.2018.04.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2018] [Revised: 04/02/2018] [Accepted: 04/03/2018] [Indexed: 02/03/2023]
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5
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Sugiki T, Kobayashi N, Fujiwara T. Modern Technologies of Solution Nuclear Magnetic Resonance Spectroscopy for Three-dimensional Structure Determination of Proteins Open Avenues for Life Scientists. Comput Struct Biotechnol J 2017; 15:328-339. [PMID: 28487762 PMCID: PMC5408130 DOI: 10.1016/j.csbj.2017.04.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Revised: 03/31/2017] [Accepted: 04/03/2017] [Indexed: 02/07/2023] Open
Abstract
Nuclear magnetic resonance (NMR) spectroscopy is a powerful technique for structural studies of chemical compounds and biomolecules such as DNA and proteins. Since the NMR signal sensitively reflects the chemical environment and the dynamics of a nuclear spin, NMR experiments provide a wealth of structural and dynamic information about the molecule of interest at atomic resolution. In general, structural biology studies using NMR spectroscopy still require a reasonable understanding of the theory behind the technique and experience on how to recorded NMR data. Owing to the remarkable progress in the past decade, we can easily access suitable and popular analytical resources for NMR structure determination of proteins with high accuracy. Here, we describe the practical aspects, workflow and key points of modern NMR techniques used for solution structure determination of proteins. This review should aid NMR specialists aiming to develop new methods that accelerate the structure determination process, and open avenues for non-specialist and life scientists interested in using NMR spectroscopy to solve protein structures.
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Affiliation(s)
- Toshihiko Sugiki
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Naohiro Kobayashi
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Toshimichi Fujiwara
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan
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6
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Cowman PF, Parravicini V, Kulbicki M, Floeter SR. The biogeography of tropical reef fishes: endemism and provinciality through time. Biol Rev Camb Philos Soc 2017; 92:2112-2130. [DOI: 10.1111/brv.12323] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 01/23/2017] [Accepted: 01/26/2017] [Indexed: 12/25/2022]
Affiliation(s)
- Peter F. Cowman
- Department of Ecology and Evolutionary Biology; Yale University; New Haven CT 06511 U.S.A
- Centre of Excellence for Coral Reef Studies; James Cook University; Townsville 4811 Australia
| | - Valeriano Parravicini
- Ecole Pratique des Hautes Etudes, USR 3278 EPHE-CNRS-UPVD, Labex Corail, CRIOBE; 66860 Perpignan France
| | - Michel Kulbicki
- Institut de Recherche pour le développement (IRD), UMR Entropie-Labex CORAIL; Université de Perpignan; 66000 Perpignan France
| | - Sergio R. Floeter
- Depto. de Ecologia e Zoologia, Marine Macroecology and Biogeography Laboratory, CCB; Universidade Federal de Santa Catarina; Florianópolis 88040-900 Brazil
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7
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Strain analysis of protein structures and low dimensionality of mechanical allosteric couplings. Proc Natl Acad Sci U S A 2016; 113:E5847-E5855. [PMID: 27655887 DOI: 10.1073/pnas.1609462113] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In many proteins, especially allosteric proteins that communicate regulatory states from allosteric to active sites, structural deformations are functionally important. To understand these deformations, dynamical experiments are ideal but challenging. Using static structural information, although more limited than dynamical analysis, is much more accessible. Underused for protein analysis, strain is the natural quantity for studying local deformations. We calculate strain tensor fields for proteins deformed by ligands or thermal fluctuations using crystal and NMR structure ensembles. Strains-primarily shears-show deformations around binding sites. These deformations can be induced solely by ligand binding at distant allosteric sites. Shears reveal quasi-2D paths of mechanical coupling between allosteric and active sites that may constitute a widespread mechanism of allostery. We argue that strain-particularly shear-is the most appropriate quantity for analysis of local protein deformations. This analysis can reveal mechanical and biological properties of many proteins.
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8
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Bietz S, Fährrolfes R, Rarey M. The Art of Compiling Protein Binding Site Ensembles. Mol Inform 2016; 35:593-598. [PMID: 27870245 DOI: 10.1002/minf.201600043] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Accepted: 04/25/2016] [Indexed: 01/24/2023]
Abstract
Structure-based drug design starts with the collection, preparation, and initial analysis of protein structures. With more than 115,000 structures publically available in the Protein Data Bank (PDB), fully automated processes reliably performing these important preprocessing steps are needed. Several tools are available for these tasks, however, most of them do not address the special needs of scientists interested in protein-ligand interactions. In this paper, we summarize our research activities towards an automated processing pipeline from raw PDB data towards ready-to-use protein binding site ensembles. Starting from a single protein structure, the pipeline covers the following phases: Extracting structurally related binding sites from the PDB, aligning disconnected binding site sequences, resolving tautomeric forms and protonation, orienting hydrogens and flippable side-chains, structurally aligning the multitude of binding sites, and performing a reasonable reduction of ensemble structures. The pipeline, named SIENA, creates protein-structural ensembles for the analysis of protein flexibility, molecular design efforts like docking or de novo design within seconds. For the first time, we are able to process the whole PDB in order to create a large collection of protein binding site ensembles. SIENA is available as part of the ZBH ProteinsPlus webserver under http://proteinsplus.zbh.uni-hamburg.de.
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Affiliation(s)
- Stefan Bietz
- University of Hamburg, ZBH -, Center for Bioinformatics, Bundesstraße 43, 20146, Hamburg, Germany
| | - Rainer Fährrolfes
- University of Hamburg, ZBH -, Center for Bioinformatics, Bundesstraße 43, 20146, Hamburg, Germany
| | - Matthias Rarey
- University of Hamburg, ZBH -, Center for Bioinformatics, Bundesstraße 43, 20146, Hamburg, Germany
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9
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Bietz S, Rarey M. SIENA: Efficient Compilation of Selective Protein Binding Site Ensembles. J Chem Inf Model 2016; 56:248-59. [PMID: 26759067 DOI: 10.1021/acs.jcim.5b00588] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Structural flexibility of proteins has an important influence on molecular recognition and enzymatic function. In modeling, structure ensembles are therefore often applied as a valuable source of alternative protein conformations. However, their usage is often complicated by structural artifacts and inconsistent data annotation. Here, we present SIENA, a new computational approach for the automated assembly and preprocessing of protein binding site ensembles. Starting with an arbitrarily defined binding site in a single protein structure, SIENA searches for alternative conformations of the same or sequentially closely related binding sites. The method is based on an indexed database for identifying perfect k-mer matches and a recently published algorithm for the alignment of protein binding site conformations. Furthermore, SIENA provides a new algorithm for the interaction-based selection of binding site conformations which aims at covering all known ligand-binding geometries. Various experiments highlight that SIENA is able to generate comprehensive and well selected binding site ensembles improving the compatibility to both known and unconsidered ligand molecules. Starting with the whole PDB as data source, the computation time of the whole ensemble generation takes only a few seconds. SIENA is available via a Web service at www.zbh.uni-hamburg.de/siena .
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Affiliation(s)
- Stefan Bietz
- Center for Bioinformatics, University of Hamburg , Bundesstrasse 43, 20146 Hamburg, Germany
| | - Matthias Rarey
- Center for Bioinformatics, University of Hamburg , Bundesstrasse 43, 20146 Hamburg, Germany
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10
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Huang Z, Wong CF. Inexpensive Method for Selecting Receptor Structures for Virtual Screening. J Chem Inf Model 2015; 56:21-34. [PMID: 26651874 DOI: 10.1021/acs.jcim.5b00299] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This article introduces a screening performance index (SPI) to help select from a number of experimental structures one or a few that are more likely to identify more actives among its top hits from virtual screening of a compound library. It achieved this by docking only known actives to the experimental structures without considering a large number of decoys to reduce computational costs. The SPI is calculated by using the docking energies of the actives to all the receptor structures. We evaluated the performance of the SPI by applying it to study eight protein systems: fatty acid binding protein adipocyte FABP4, serine/threonine-protein kinase BRAF, beta-1 adrenergic receptor ADRB1, TGF-beta receptor type I TGFR1, adenosylhomocysteinase SAHH, thyroid hormone receptor beta-1 THB, phospholipase A2 group IIA PA2GA, and cytochrome P450 3a4 CP3A4. We found that the SPI agreed with the results from other popular performance metrics such as Boltzmann-Enhanced Discrimination Receiver Operator Characteristics (BEDROC), Robust Initial Enhancement (RIE), Area Under Accumulation Curve (AUAC), and Enrichment Factor (EF) but is less expensive to calculate. SPI also performed better than the best docking energy, the molecular volume of the bound ligand, and the resolution of crystal structure in selecting good receptor structures for virtual screening. The implications of these findings were further discussed in the context of ensemble docking, in situations when no experimental structure for the targeted protein was available, or under circumstances when quick choices of receptor structures need to be made before quantitative indexes such as the SPI and BEDROC can be calculated.
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Affiliation(s)
- Zunnan Huang
- China-America Cancer Research Institute, Guangdong Provincial Key Laboratory of Medical Molecular Diagnostics, Dongguan Scientific Research Center, Guangdong Medical University , Dongguan, Guangdong Province, P. R. China , 523808
| | - Chung F Wong
- Department of Chemistry and Biochemistry and Center for Nanoscience, University of Missouri-Saint Louis , One University Boulevard, St. Louis, Missouri 63121, United States
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11
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Tsai CJ, Liu S, Hung CL, Jhong SR, Sung TC, Chiang YW. BAX-induced apoptosis can be initiated through a conformational selection mechanism. Structure 2014; 23:139-148. [PMID: 25497728 DOI: 10.1016/j.str.2014.10.016] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Revised: 10/23/2014] [Accepted: 10/29/2014] [Indexed: 02/01/2023]
Abstract
BAX protein plays a key role in the mitochondria-mediated apoptosis. However, it remains unclear by what mechanism BAX is triggered to initiate apoptosis. Here, we reveal the mechanism using electron spin resonance (ESR) techniques. An inactive BAX monomer was found to exhibit conformational heterogeneity and exist at equilibrium in two conformations, one of which has never been reported. We show that upon apoptotic stimulus by BH3-only peptides, BAX can be induced to convert into either a ligand-bound monomer or an oligomer through a conformational selection mechanism. The kinetics of reaction is studied by means of time-resolved ESR, allowing a direct in situ observation for the transformation of BAX from the native to the bound states. In vitro mitochondrial assays provide further discrimination between the proposed BAX states, thereby revealing a population-shift allosteric mechanism in the process. BAX's apoptotic function is shown to critically depend on excursions between different structural conformations.
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Affiliation(s)
- Chia-Jung Tsai
- Department of Chemistry and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Sophia Liu
- Department of Chemistry and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Chien-Lun Hung
- Department of Chemistry and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Siao-Ru Jhong
- Department of Chemistry and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Tai-Ching Sung
- Department of Chemistry and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Yun-Wei Chiang
- Department of Chemistry and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan.
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12
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Snyder DA, Grullon J, Huang YJ, Tejero R, Montelione GT. The expanded FindCore method for identification of a core atom set for assessment of protein structure prediction. Proteins 2014; 82 Suppl 2:219-30. [PMID: 24327305 DOI: 10.1002/prot.24490] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 11/14/2013] [Accepted: 11/19/2013] [Indexed: 11/09/2022]
Abstract
Maximizing the scientific impact of NMR-based structure determination requires robust and statistically sound methods for assessing the precision of NMR-derived structures. In particular, a method to define a core atom set for calculating superimpositions and validating structure predictions is critical to the use of NMR-derived structures as targets in the CASP competition. FindCore (Snyder and Montelione, Proteins 2005;59:673-686) is a superimposition independent method for identifying a core atom set and partitioning that set into domains. However, as FindCore optimizes superimposition by sensitively excluding not-well-defined atoms, the FindCore core may not comprise all atoms suitable for use in certain applications of NMR structures, including the CASP assessment process. Adapting the FindCore approach to assess predicted models against experimental NMR structures in CASP10 required modification of the FindCore method. This paper describes conventions and a standard protocol to calculate an "Expanded FindCore" atom set suitable for validation and application in biological and biophysical contexts. A key application of the Expanded FindCore method is to identify a core set of atoms in the experimental NMR structure for which it makes sense to validate predicted protein structure models. We demonstrate the application of this Expanded FindCore method in characterizing well-defined regions of 18 NMR-derived CASP10 target structures. The Expanded FindCore protocol defines "expanded core atom sets" that match an expert's intuition of which parts of the structure are sufficiently well defined to use in assessing CASP model predictions. We also illustrate the impact of this analysis on the CASP GDT assessment scores.
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Affiliation(s)
- David A Snyder
- Department of Chemistry, William Paterson University, Wayne, New Jersey, 07470
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13
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Zhang W, Zhang T, Zhang H, Hao Q. Crystallographic phasing with NMR models: an envelope approach. ACTA ACUST UNITED AC 2014; 70:1977-82. [DOI: 10.1107/s1399004714009754] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 04/30/2014] [Indexed: 11/10/2022]
Abstract
X-ray crystallography and NMR are complementary tools in structural biology. However, it is often difficult to use NMR structures as search models in molecular replacement (MR) to phase crystallographic data. In this study, a new approach is reported utilizing a molecular envelope of NMR structures for MR phasing with the programFSEARCHat low resolution (about 6 Å). Several targets with both crystallographic and NMR structures available have been tested.FSEARCHwas able to find the correct translation and orientation of the search model in the crystallographic unit cell, while conventional MR procedures were unsuccessful.
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14
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Vuister GW, Fogh RH, Hendrickx PMS, Doreleijers JF, Gutmanas A. An overview of tools for the validation of protein NMR structures. JOURNAL OF BIOMOLECULAR NMR 2014; 58:259-285. [PMID: 23877928 DOI: 10.1007/s10858-013-9750-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 06/04/2013] [Indexed: 06/02/2023]
Abstract
Biomolecular structures at atomic resolution present a valuable resource for the understanding of biology. NMR spectroscopy accounts for 11% of all structures in the PDB repository. In response to serious problems with the accuracy of some of the NMR-derived structures and in order to facilitate proper analysis of the experimental models, a number of program suites are available. We discuss nine of these tools in this review: PROCHECK-NMR, PSVS, GLM-RMSD, CING, Molprobity, Vivaldi, ResProx, NMR constraints analyzer and QMEAN. We evaluate these programs for their ability to assess the structural quality, restraints and their violations, chemical shifts, peaks and the handling of multi-model NMR ensembles. We document both the input required by the programs and output they generate. To discuss their relative merits we have applied the tools to two representative examples from the PDB: a small, globular monomeric protein (Staphylococcal nuclease from S. aureus, PDB entry 2kq3) and a small, symmetric homodimeric protein (a region of human myosin-X, PDB entry 2lw9).
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Affiliation(s)
- Geerten W Vuister
- Department of Biochemistry, School of Biological Sciences, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester, LE1 9HN, UK,
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15
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Montelione GT, Nilges M, Bax A, Güntert P, Herrmann T, Richardson JS, Schwieters CD, Vranken WF, Vuister GW, Wishart DS, Berman HM, Kleywegt GJ, Markley JL. Recommendations of the wwPDB NMR Validation Task Force. Structure 2014; 21:1563-70. [PMID: 24010715 DOI: 10.1016/j.str.2013.07.021] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 07/19/2013] [Accepted: 07/29/2013] [Indexed: 11/25/2022]
Abstract
As methods for analysis of biomolecular structure and dynamics using nuclear magnetic resonance spectroscopy (NMR) continue to advance, the resulting 3D structures, chemical shifts, and other NMR data are broadly impacting biology, chemistry, and medicine. Structure model assessment is a critical area of NMR methods development, and is an essential component of the process of making these structures accessible and useful to the wider scientific community. For these reasons, the Worldwide Protein Data Bank (wwPDB) has convened an NMR Validation Task Force (NMR-VTF) to work with wwPDB partners in developing metrics and policies for biomolecular NMR data harvesting, structure representation, and structure quality assessment. This paper summarizes the recommendations of the NMR-VTF, and lays the groundwork for future work in developing standards and metrics for biomolecular NMR structure quality assessment.
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Affiliation(s)
- Gaetano T Montelione
- Center for Advanced Biotechnology and Medicine, Department of Molecular Biology and Biochemistry, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA; Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA.
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16
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Kobayashi N. A robust method for quantitative identification of ordered cores in an ensemble of biomolecular structures by non-linear multi-dimensional scaling using inter-atomic distance variance matrix. JOURNAL OF BIOMOLECULAR NMR 2014; 58:61-67. [PMID: 24384868 DOI: 10.1007/s10858-013-9805-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Accepted: 12/10/2013] [Indexed: 06/03/2023]
Abstract
Superpositioning of atoms in an ensemble of biomolecules is a common task in a variety of fields in structural biology. Although several automated tools exist based on previously established methods, manual operations to define the atoms in the ordered regions are usually preferred. The task is difficult and lacks output efficiency for multi-core proteins having complicated folding topology. The new method presented here can systematically and quantitatively achieve the identification of ordered cores even for molecules containing multiple cores linked with flexible loops. In contrast to established methods, this method treats the variance of inter-atomic distances in an ensemble as information content using a non-linear (NL) function, and then subjects it to multi-dimensional scaling (MDS) to embed the row vectors in the inter-atomic distance variance matrix into a lower dimensional matrix. The plots of the identified atom groups in a one or two-dimensional map enables users to visually and intuitively infer well-ordered atoms in an ensemble, as well as to automatically identify them by the standard clustering methods. The performance of the NL-MDS method has been examined for number of structure ensembles studied by nuclear magnetic resonance, demonstrating that the method can be more suitable for structural analysis of multi-core proteins in comparison to previously established methods.
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Affiliation(s)
- Naohiro Kobayashi
- Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka, 565-0871, Japan,
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17
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Rosato A, Tejero R, Montelione GT. Quality assessment of protein NMR structures. Curr Opin Struct Biol 2013; 23:715-24. [PMID: 24060334 DOI: 10.1016/j.sbi.2013.08.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Accepted: 08/14/2013] [Indexed: 10/26/2022]
Abstract
Biomolecular NMR structures are now routinely used in biology, chemistry, and bioinformatics. Methods and metrics for assessing the accuracy and precision of protein NMR structures are beginning to be standardized across the biological NMR community. These include both knowledge-based assessment metrics, parameterized from the database of protein structures, and model versus data assessment metrics. On line servers are available that provide comprehensive protein structure quality assessment reports, and efforts are in progress by the world-wide Protein Data Bank (wwPDB) to develop a biomolecular NMR structure quality assessment pipeline as part of the structure deposition process. These quality assessment metrics and standards will aid NMR spectroscopists in determining more accurate structures, and increase the value and utility of these structures for the broad scientific community.
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Affiliation(s)
- Antonio Rosato
- Magnetic Resonance Center and Department of Chemistry, University of Florence, 50019 Sesto Fiorentino, Italy
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Wan X, Ma Y, McClendon CL, Huang LJS, Huang N. Ab initio modeling and experimental assessment of Janus Kinase 2 (JAK2) kinase-pseudokinase complex structure. PLoS Comput Biol 2013; 9:e1003022. [PMID: 23592968 PMCID: PMC3616975 DOI: 10.1371/journal.pcbi.1003022] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Accepted: 02/20/2013] [Indexed: 01/07/2023] Open
Abstract
The Janus Kinase 2 (JAK2) plays essential roles in transmitting signals from multiple cytokine receptors, and constitutive activation of JAK2 results in hematopoietic disorders and oncogenesis. JAK2 kinase activity is negatively regulated by its pseudokinase domain (JH2), where the gain-of-function mutation V617F that causes myeloproliferative neoplasms resides. In the absence of a crystal structure of full-length JAK2, how JH2 inhibits the kinase domain (JH1), and how V617F hyperactivates JAK2 remain elusive. We modeled the JAK2 JH1-JH2 complex structure using a novel informatics-guided protein-protein docking strategy. A detailed JAK2 JH2-mediated auto-inhibition mechanism is proposed, where JH2 traps the activation loop of JH1 in an inactive conformation and blocks the movement of kinase αC helix through critical hydrophobic contacts and extensive electrostatic interactions. These stabilizing interactions are less favorable in JAK2-V617F. Notably, several predicted binding interfacial residues in JH2 were confirmed to hyperactivate JAK2 kinase activity in site-directed mutagenesis and BaF3/EpoR cell transformation studies. Although there may exist other JH2-mediated mechanisms to control JH1, our JH1-JH2 structural model represents a verifiable working hypothesis for further experimental studies to elucidate the role of JH2 in regulating JAK2 in both normal and pathological settings.
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Affiliation(s)
- Xiaobo Wan
- Graduate School in Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
- National Institute of Biological Sciences, Beijing, Zhongguancun Life Science Park, Changping District, Beijing, China
| | - Yue Ma
- Department of Cell Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Christopher L. McClendon
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, San Diego, California, United States of America
| | - Lily Jun-shen Huang
- Department of Cell Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Niu Huang
- Graduate School in Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
- National Institute of Biological Sciences, Beijing, Zhongguancun Life Science Park, Changping District, Beijing, China
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Gessmann R, Axford D, Owen RL, Brückner H, Petratos K. Four complete turns of a curved 3₁₀-helix at atomic resolution: the crystal structure of the peptaibol trichovirin I-4A in a polar environment suggests a transition to α-helix for membrane function. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2012; 68:109-16. [PMID: 22281739 DOI: 10.1107/s090744491105133x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Accepted: 11/29/2011] [Indexed: 09/03/2023]
Abstract
The first crystal structure of a member of peptaibol antibiotic subfamily 4, trichovirin I-4A (14 residues), has been determined by direct methods and refined at atomic resolution. The monoclinic unit cell has two molecules in the asymmetric unit. Both molecules assume a 3₁₀ right-handed helical conformation and are significantly bent. The molecules pack loosely along the crystallographic twofold axis, forming two large tunnels between symmetry-related molecules in which no ordered solvent could be located. Carbonyl O atoms which are not involved in intramolecular hydrogen bonding participate in close van der Waals interactions with apolar groups. The necessary amphipathicity for biological activity of peptaibols is not realised in the crystal structure. Hence, a structural change of trichovirin to an α-helical conformation is proposed for membrane integration and efficient water/ion transportation across the lipid bilayer.
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Bottegoni G, Rocchia W, Cavalli A. Application of conformational clustering in protein-ligand docking. Methods Mol Biol 2012; 819:169-186. [PMID: 22183537 DOI: 10.1007/978-1-61779-465-0_12] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Protein-Ligand docking is a powerful technique routinely employed in structure-based drug design. Despite many reported success stories, docking is not always able to provide an accurate and easily interpretable prediction of the structure of the bound complex formed by a small organic molecule and a pharmacologically relevant target. Cluster analysis can represent a versatile and readily available postprocessing tool to be employed in combination with protein-ligand docking to simplify the evaluation of the results and help to overcome present limitations of docking protocols.
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Affiliation(s)
- Giovanni Bottegoni
- Department of Drug Discovery and Development, Istituto Italiano di Tecnologia, Genova, Italy
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21
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Mao B, Guan R, Montelione GT. Improved technologies now routinely provide protein NMR structures useful for molecular replacement. Structure 2011; 19:757-66. [PMID: 21645849 DOI: 10.1016/j.str.2011.04.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Revised: 04/07/2011] [Accepted: 04/25/2011] [Indexed: 10/18/2022]
Abstract
Molecular replacement (MR) is widely used for addressing the phase problem in X-ray crystallography. Historically, crystallographers have had limited success using NMR structures as MR search models. Here, we report a comprehensive investigation of the utility of protein NMR ensembles as MR search models, using data for 25 pairs of X-ray and NMR structures solved and refined using modern NMR methods. Starting from NMR ensembles prepared by an improved protocol, FindCore, correct MR solutions were obtained for 22 targets. Based on these solutions, automatic model rebuilding could be done successfully. Rosetta refinement of NMR structures provided MR solutions for another two proteins. We also demonstrate that such properly prepared NMR ensembles and X-ray crystal structures have similar performance when used as MR search models for homologous structures, particularly for targets with sequence identity >40%.
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Affiliation(s)
- Binchen Mao
- Center for Advanced Biotechnology and Medicine, Rutgers, The State University of New Jersey, and Robert Wood Johnson Medical School, UMDNJ, Piscataway, NJ 08854, USA
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22
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Kirchner DK, Güntert P. Objective identification of residue ranges for the superposition of protein structures. BMC Bioinformatics 2011; 12:170. [PMID: 21592348 PMCID: PMC3120703 DOI: 10.1186/1471-2105-12-170] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Accepted: 05/18/2011] [Indexed: 11/27/2022] Open
Abstract
Background The automation of objectively selecting amino acid residue ranges for structure superpositions is important for meaningful and consistent protein structure analyses. So far there is no widely-used standard for choosing these residue ranges for experimentally determined protein structures, where the manual selection of residue ranges or the use of suboptimal criteria remain commonplace. Results We present an automated and objective method for finding amino acid residue ranges for the superposition and analysis of protein structures, in particular for structure bundles resulting from NMR structure calculations. The method is implemented in an algorithm, CYRANGE, that yields, without protein-specific parameter adjustment, appropriate residue ranges in most commonly occurring situations, including low-precision structure bundles, multi-domain proteins, symmetric multimers, and protein complexes. Residue ranges are chosen to comprise as many residues of a protein domain that increasing their number would lead to a steep rise in the RMSD value. Residue ranges are determined by first clustering residues into domains based on the distance variance matrix, and then refining for each domain the initial choice of residues by excluding residues one by one until the relative decrease of the RMSD value becomes insignificant. A penalty for the opening of gaps favours contiguous residue ranges in order to obtain a result that is as simple as possible, but not simpler. Results are given for a set of 37 proteins and compared with those of commonly used protein structure validation packages. We also provide residue ranges for 6351 NMR structures in the Protein Data Bank. Conclusions The CYRANGE method is capable of automatically determining residue ranges for the superposition of protein structure bundles for a large variety of protein structures. The method correctly identifies ordered regions. Global structure superpositions based on the CYRANGE residue ranges allow a clear presentation of the structure, and unnecessary small gaps within the selected ranges are absent. In the majority of cases, the residue ranges from CYRANGE contain fewer gaps and cover considerably larger parts of the sequence than those from other methods without significantly increasing the RMSD values. CYRANGE thus provides an objective and automatic method for standardizing the choice of residue ranges for the superposition of protein structures.
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Affiliation(s)
- Donata K Kirchner
- Institute of Biophysical Chemistry, Center for Biomolecular Magnetic Resonance, and Frankfurt Institute for Advanced Studies, Goethe University Frankfurt am Main, Max-von-Laue-Str, 9, 60438 Frankfurt am Main, Germany
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23
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Bolognesi ML, Bartolini M, Mancini F, Chiriano G, Ceccarini L, Rosini M, Milelli A, Tumiatti V, Andrisano V, Melchiorre C. Bis(7)-tacrine derivatives as multitarget-directed ligands: Focus on anticholinesterase and antiamyloid activities. ChemMedChem 2010; 5:1215-20. [PMID: 20486153 DOI: 10.1002/cmdc.201000086] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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24
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Targeting Alzheimer’s disease: Novel indanone hybrids bearing a pharmacophoric fragment of AP2238. Bioorg Med Chem 2010; 18:1749-60. [DOI: 10.1016/j.bmc.2010.01.071] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Revised: 01/22/2010] [Accepted: 01/29/2010] [Indexed: 11/21/2022]
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25
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Schneider M, Fu X, Keating AE. X-ray vs. NMR structures as templates for computational protein design. Proteins 2009; 77:97-110. [PMID: 19422060 DOI: 10.1002/prot.22421] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Certain protein-design calculations involve using an experimentally determined high-resolution structure as a template to identify new sequences that can adopt the same fold. This approach has led to the successful design of many novel, well-folded, native-like proteins. Although any atomic-resolution structure can serve as a template in such calculations, most successful designs have used high-resolution crystal structures. Because there are many proteins for which crystal structures are not available, it is of interest whether nuclear magnetic resonance (NMR) templates are also appropriate. We have analyzed differences between using X-ray and NMR templates in side-chain repacking and design calculations. We assembled a database of 29 proteins for which both a high-resolution X-ray structure and an ensemble of NMR structures are available. Using these pairs, we compared the rotamericity, chi(1)-angle recovery, and native-sequence recovery of X-ray and NMR templates. We carried out design using RosettaDesign on both types of templates, and compared the energies and packing qualities of the resulting structures. Overall, the X-ray structures were better templates for use with Rosetta. However, for approximately 20% of proteins, a member of the reported NMR ensemble gave rise to designs with similar properties. Re-evaluating RosettaDesign structures with other energy functions indicated much smaller differences between the two types of templates. Ultimately, experiments are required to confirm the utility of particular X-ray and NMR templates. But our data suggest that the lack of a high-resolution X-ray structure should not preclude attempts at computational design if an NMR ensemble is available.
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26
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Velankar S, Best C, Beuth B, Boutselakis CH, Cobley N, Sousa Da Silva AW, Dimitropoulos D, Golovin A, Hirshberg M, John M, Krissinel EB, Newman R, Oldfield T, Pajon A, Penkett CJ, Pineda-Castillo J, Sahni G, Sen S, Slowley R, Suarez-Uruena A, Swaminathan J, van Ginkel G, Vranken WF, Henrick K, Kleywegt GJ. PDBe: Protein Data Bank in Europe. Nucleic Acids Res 2009; 38:D308-17. [PMID: 19858099 PMCID: PMC2808887 DOI: 10.1093/nar/gkp916] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The Protein Data Bank in Europe (PDBe) (http://www.ebi.ac.uk/pdbe/) is actively working with its Worldwide Protein Data Bank partners to enhance the quality and consistency of the international archive of bio-macromolecular structure data, the Protein Data Bank (PDB). PDBe also works closely with its collaborators at the European Bioinformatics Institute and the scientific community around the world to enhance its databases and services by adding curated and actively maintained derived data to the existing structural data in the PDB. We have developed a new database infrastructure based on the remediated PDB archive data and a specially designed database for storing information on interactions between proteins and bound molecules. The group has developed new services that allow users to carry out simple textual queries or more complex 3D structure-based queries. The newly designed 'PDBeView Atlas pages' provide an overview of an individual PDB entry in a user-friendly layout and serve as a starting point to further explore the information available in the PDBe database. PDBe's active involvement with the X-ray crystallography, Nuclear Magnetic Resonance spectroscopy and cryo-Electron Microscopy communities have resulted in improved tools for structure deposition and analysis.
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Affiliation(s)
- S Velankar
- Protein Databank in Europe, EMBL-EBI, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SD, UK.
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27
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Grazioso G, Cavalli A, De Amici M, Recanatini M, De Micheli C. Alpha7 nicotinic acetylcholine receptor agonists: prediction of their binding affinity through a molecular mechanics Poisson-Boltzmann surface area approach. J Comput Chem 2008; 29:2593-602. [PMID: 18478580 DOI: 10.1002/jcc.21019] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A group of agonists for the alpha7 neuronal nicotinic acetylcholine receptors (nAChRs) was investigated, and their free energies of binding DeltaG(bind) were calculated by applying the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) approach. This method, based on molecular dynamics simulations of fully solvated protein-ligand complexes, allowed us to estimate the contribution of both polar and nonpolar terms as well as the entropy to the overall free energy of binding. The calculated results were in a good agreement with the experimentally determined DeltaG(bind) values, thereby pointing to the MM-PBSA protocol as a valuable computational tool for the rational design of specific agents targeting the neuronal alpha7 nAChR subtypes.
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Affiliation(s)
- Giovanni Grazioso
- Istituto di Chimica Farmaceutica e Tossicologica "Pietro Pratesi", Università degli Studi di Milano, Via Mangiagalli 25, 20133 Milano, Italy
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28
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Abstract
MOTIVATION Protein structure ensembles provide important insight into the dynamics and function of a protein and contain information that is not captured with a single static structure. However, it is not clear a priori to what extent the variability within an ensemble is caused by internal structural changes. Additional variability results from overall translations and rotations of the molecule. And most experimental data do not provide information to relate the structures to a common reference frame. To report meaningful values of intrinsic dynamics, structural precision, conformational entropy, etc., it is therefore important to disentangle local from global conformational heterogeneity. RESULTS We consider the task of disentangling local from global heterogeneity as an inference problem. We use probabilistic methods to infer from the protein ensemble missing information on reference frames and stable conformational sub-states. To this end, we model a protein ensemble as a mixture of Gaussian probability distributions of either entire conformations or structural segments. We learn these models from a protein ensemble using the expectation-maximization algorithm. Our first model can be used to find multiple conformers in a structure ensemble. The second model partitions the protein chain into locally stable structural segments or core elements and less structured regions typically found in loops. Both models are simple to implement and contain only a single free parameter: the number of conformers or structural segments. Our models can be used to analyse experimental ensembles, molecular dynamics trajectories and conformational change in proteins. AVAILABILITY The Python source code for protein ensemble analysis is available from the authors upon request.
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Affiliation(s)
- Michael Hirsch
- Department of Empirical Inference, Max-Planck-Institute for Biological Cybernetics, Spemannstrasse 38, 72076 Tübingen, Germany
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29
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Kiviranta PH, Salo HS, Leppänen J, Rinne VM, Kyrylenko S, Kuusisto E, Suuronen T, Salminen A, Poso A, Lahtela-Kakkonen M, Wallén EAA. Characterization of the binding properties of SIRT2 inhibitors with a N-(3-phenylpropenoyl)-glycine tryptamide backbone. Bioorg Med Chem 2008; 16:8054-62. [PMID: 18701307 DOI: 10.1016/j.bmc.2008.07.059] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2008] [Accepted: 07/22/2008] [Indexed: 12/01/2022]
Abstract
SIRT2 inhibitors with a N-(3-phenylpropenoyl)-glycine tryptamide backbone were studied. This backbone has been developed in our group, and it is derived from a compound originally found by virtual screening. In addition, compounds with a smaller 3-phenylpropenoic acid tryptamide backbone were also included in the study. Binding modes for the new compounds and the previously reported compounds were analyzed with molecular modelling methods. The approach, which included a combination of molecular dynamics, molecular docking and cluster analysis, showed that certain docking poses were favourable despite the conformational variation in the target protein. The N-(3-phenylpropenoyl)-glycine tryptamide backbone is also a good backbone for SIRT2 inhibitors, and the series of compounds includes several potent SIRT2 inhibitors.
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Affiliation(s)
- Päivi H Kiviranta
- Department of Pharmaceutical Chemistry, University of Kuopio, PO Box 1627, 70211 Kuopio, Finland.
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30
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Domingues FS, Rahnenführer J, Lengauer T. Conformational analysis of alternative protein structures. Bioinformatics 2007; 23:3131-8. [PMID: 17933849 DOI: 10.1093/bioinformatics/btm499] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
MOTIVATION Alternative structural models determined experimentally are available for an increasing number of proteins. Structural and functional studies of these proteins need to take these models into consideration as they can present considerable structural differences. The characterization of the structural differences and similarities between these models is a fundamental task in structural biology requiring appropriate methods. RESULTS We propose a method for characterizing sets of alternative structural models. Three types of analysis are performed: grouping according to structural similarity, visualization and detection of structural variation and comparison of subsets for identifying and locating distinct conformational states. The alpha carbon atoms are used in order to analyse the backbone conformations. Alternatively, side-chain atoms are used for detailed conformational analysis of specific sites. The method takes into account estimates of atom coordinate uncertainty. The invariant regions are used to generate optimal superpositions of these models. We present the results obtained for three proteins showing different degrees of conformational variability: relative motion of two structurally conserved subdomains, a disordered subdomain and flexibility in the functional site associated with ligand binding. The method has been applied in the analysis of the alternative models available in SCOP. Considerable structural variability can be observed for most proteins. AVAILABILITY The results of the analysis of the SCOP alternative models, the estimates of coordinate uncertainty as well as the source code of the implementation are available in the STRuster web site: http://struster.bioinf.mpi-inf.mpg.de.
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31
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Bolognesi ML, Banzi R, Bartolini M, Cavalli A, Tarozzi A, Andrisano V, Minarini A, Rosini M, Tumiatti V, Bergamini C, Fato R, Lenaz G, Hrelia P, Cattaneo A, Recanatini M, Melchiorre C. Novel class of quinone-bearing polyamines as multi-target-directed ligands to combat Alzheimer's disease. J Med Chem 2007; 50:4882-97. [PMID: 17850125 DOI: 10.1021/jm070559a] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
One of the characteristics of Alzheimer's disease (AD) that hinders the discovery of effective disease-modifying therapies is the multifactorial nature of its etiopathology. To circumvent this drawback, the use of multi-target-directed ligands (MTDLs) has recently been proposed as a means of simultaneously hitting several targets involved in the development of the AD syndrome. In this paper, a new class of MTDLs based on a polyamine-quinone skeleton, whose lead (memoquin, 2) showed promising properties in preclinical investigations (Cavalli et al. Angew. Chem., Int. Ed. 2007, 46, 3689-3692), is described. 3-29 were tested in vitro against a number of isolated AD-related targets, namely, AChE and BChE, and Abeta aggregation (both AChE-mediated and self-induced). Furthermore, the ability of the compounds to counteract the oxidative stress in a human neuronal-like cellular system (SH-SY5Y cells) was assayed, in both the presence and absence of NQO1, an enzyme able to generate and maintain the reduced form of quinone.
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Affiliation(s)
- Maria Laura Bolognesi
- Department of Pharmaceutical Sciences, Alma Mater Studiorum, University of Bologna, Via Belmeloro 6, Italy.
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32
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Rainey JK, Fliegel L, Sykes BD. Strategies for dealing with conformational sampling in structural calculations of flexible or kinked transmembrane peptides. Biochem Cell Biol 2007; 84:918-29. [PMID: 17215879 DOI: 10.1139/o06-178] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Peptides corresponding to transmembrane (TM) segments from membrane proteins provide a potential route for the determination of membrane protein structure. We have determined that 2 functionally critical TM segments from the mammalian Na+/H+ exchanger display well converged structure in regions separated by break points. The flexibility of these break points results in conformational sampling in solution. A brief review of available NMR structures of helical membrane proteins demonstrates that there are a number of published structures showing similar properties. Such flexibility is likely indicative of kinks in the full-length protein. This minireview focuses on methods and protocols for NMR structure calculation and analysis of peptide structures under conditions of conformational sampling. The methods outlined allow the identification and analysis of structured peptides containing break points owing to conformational sampling and the differentiation between oligomerization and ensemble-averaged observation of multiple peptide conformations.
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Affiliation(s)
- Jan K Rainey
- Protein Engineering Network of Centres of Excellence and Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
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33
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Snyder DA, Montelione GT. Clustering algorithms for identifying core atom sets and for assessing the precision of protein structure ensembles. Proteins 2006; 59:673-86. [PMID: 15822099 DOI: 10.1002/prot.20402] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
An important open question in the field of NMR-based biomolecular structure determination is how best to characterize the precision of the resulting ensemble of structures. Typically, the RMSD, as minimized in superimposing the ensemble of structures, is the preferred measure of precision. However, the presence of poorly determined atomic coordinates and multiple "RMSD-stable domains"--locally well-defined regions that are not aligned in global superimpositions--complicate RMSD calculations. In this paper, we present a method, based on a novel, structurally defined order parameter, for identifying a set of core atoms to use in determining superimpositions for RMSD calculations. In addition we present a method for deciding whether to partition that core atom set into "RMSD-stable domains" and, if so, how to determine partitioning of the core atom set. We demonstrate our algorithm and its application in calculating statistically sound RMSD values by applying it to a set of NMR-derived structural ensembles, superimposing each RMSD-stable domain (or the entire core atom set, where appropriate) found in each protein structure under consideration. A parameter calculated by our algorithm using a novel, kurtosis-based criterion, the epsilon-value, is a measure of precision of the superimposition that complements the RMSD. In addition, we compare our algorithm with previously described algorithms for determining core atom sets. The methods presented in this paper for biomolecular structure superimposition are quite general, and have application in many areas of structural bioinformatics and structural biology.
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Affiliation(s)
- David A Snyder
- Center for Advanced Biotechnology and Medicine, Department of Molecular Biology and Biochemistry, and Northeast Structural Genomics Consortium, Rutgers University, Piscataway, New Jersey 08854, USA
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34
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Bottegoni G, Cavalli A, Recanatini M. A Comparative Study on the Application of Hierarchical−Agglomerative Clustering Approaches to Organize Outputs of Reiterated Docking Runs. J Chem Inf Model 2006; 46:852-62. [PMID: 16563017 DOI: 10.1021/ci050141q] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Reiterated runs of standard docking protocols usually provide a collection of possible binding modes rather than pinpoint a single solution. Usually, this ensemble is then ranked by means of an energy-based scoring function. However, since many degrees of approximation have to be introduced in the computation of the binding free energy, scoring functions cannot always rank the experimental pose among the top scorers. Cluster analysis might help to overcome this limit, provided that data clusterability has been earlier assessed. In this paper, first, we present a modified version of a test earlier developed by Hopkins to assess whether or not docking outputs show the natural tendency to be grouped in clusters. Then, we report the results of a comparative study on the application of different hierarchical-agglomerative cluster rules to partition docking outputs. The rule that was able to best manage the observed data was finally applied to the whole ensemble of poses collected from several docking tools. The combination of the average linkage rule with the cutting function developed by Sutcliffe and co-workers turned out to be an approach that meets all of the criteria required for a robust clustering protocol. Furthermore, a consensus clustering allowed us to identify the pose closest to the experimental one within a statistically significant cluster, whose number was always of few units.
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Affiliation(s)
- Giovanni Bottegoni
- Department of Pharmaceutical Sciences, University of Bologna, Via Belmeloro, 6-I-40126 Bologna, Italy
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35
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Slepkov ER, Rainey JK, Li X, Liu Y, Cheng FJ, Lindhout DA, Sykes BD, Fliegel L. Structural and Functional Characterization of Transmembrane Segment IV of the NHE1 Isoform of the Na+/H+ Exchanger. J Biol Chem 2005; 280:17863-72. [PMID: 15677483 DOI: 10.1074/jbc.m409608200] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Na(+)/H(+) exchanger isoform 1 is a ubiquitously expressed integral membrane protein that regulates intracellular pH in mammals. We characterized the structural and functional aspects of the critical transmembrane (TM) segment IV. Each residue was mutated to cysteine in cysteine-less NHE1. TM IV was exquisitely sensitive to mutation with 10 of 23 mutations causing greatly reduced expression and/or activity. The Phe(161) --> Cys mutant was inhibited by treatment with the water-soluble sulfhydryl-reactive compounds [2-(trimethylammonium)ethyl]methanethiosulfonate and [2-sulfonatoethyl]methanethiosulfonate, suggesting it is a pore-lining residue. The structure of purified TM IV peptide was determined using high resolution NMR in a CD(3)OH:CDCl(3):H(2)O mixture and in Me(2)SO. In CD(3)OH: CDCl(3):H(2)O, TM IV was structured but not as a canonical alpha-helix. Residues Asp(159)-Leu(162) were a series of beta-turns; residues Leu(165)-Pro(168) showed an extended structure, and residues Ile(169)-Phe(176) were helical in character. These three structured regions rotated quite freely with respect to the others. In Me(2)SO, the structure was much less defined. Our results demonstrate that TM IV is an unusually structured transmembrane segment that is exquisitely sensitive to mutagenesis and that Phe(161) is a pore-lining residue.
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Affiliation(s)
- Emily R Slepkov
- Membrane Protein Research Group, Department of Biochemistry, Canadian Institutes of Health Research Group in Protein Structure and Function, and Protein Engineering Network of Centers of Excellence, University of Alberta, Edmonton, Alberta, Canada
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36
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Snyder DA, Bhattacharya A, Huang YJ, Montelione GT. Assessing precision and accuracy of protein structures derived from NMR data. Proteins 2005; 59:655-61. [PMID: 15822105 DOI: 10.1002/prot.20499] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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37
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Brewer L, Corzett M, Lau EY, Balhorn R. Dynamics of protamine 1 binding to single DNA molecules. J Biol Chem 2003; 278:42403-8. [PMID: 12912999 DOI: 10.1074/jbc.m303610200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protamine molecules bind to and condense DNA in the sperm of most vertebrates, packaging the sperm genome in an inactive state until it can be reactivated following fertilization. By using methods that enable the analysis of protamine binding to individual DNA molecules, we have monitored the kinetics of DNA condensation and decondensation by protamine 1 (P1) and synthetic peptides corresponding to specific segments of the bull P1 DNA binding domain. Our results show that the number of clustered arginine residues present in the DNA binding domain is the most important factor affecting the condensation and stability of the DNA-protamine complex prior to the formation of inter-protamine disulfide cross-links. The high affinity of P1 for DNA is achieved by the coordinated binding of three anchoring domains, which together in bull P1 contain 19 Arg residues. The single DNA molecule experiments show that sequences containing two or more anchoring domains have an off-rate that is at least 3 orders of magnitude slower than those containing a single domain. The use of Arg, rather than Lys residues, and the inclusion of Tyr or Phe residues in the hinge regions between anchoring domains provide additional stability to the complex.
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Affiliation(s)
- Laurence Brewer
- Electronic Engineering Technologies Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
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Nifosì R, Reyes CM, Kollman PA. Molecular dynamics studies of the HIV-1 TAR and its complex with argininamide. Nucleic Acids Res 2000; 28:4944-55. [PMID: 11121486 PMCID: PMC115235 DOI: 10.1093/nar/28.24.4944] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The dynamic behavior of HIV-1 TAR and its complex with argininamide is investigated by means of molecular dynamics simulations starting from NMR structures, with explicit inclusion of water and periodic boundary conditions particle mesh Ewald representation of the electrostatic energy. During simulations of free and argininamide-bound TAR, local structural patterns, as determined by NMR experiments, were reproduced. An interdomain motion was observed in the simulations of free TAR, which is absent in the case of bound TAR, leading to the conclusion that the free conformation of TAR is intrinsically more flexible than the bound conformation. In particular, in the bound conformation the TAR-argininamide interface is very well ordered, as a result of the formation of a U.A.U base triple, which imposes structural constraints on the global conformation of the molecule. Free energy analysis, which includes solvation contributions, was used to evaluate the influence of van der Waals and electrostatic terms on formation of the complex and on the conformational rearrangement from free to bound TAR.
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Affiliation(s)
- R Nifosì
- Scuola Normale Superiore and Istituto Nazionale di Fisica della Materia, Piazza dei Cavalieri 7, 56126 Pisa, Italy
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39
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Abstract
To determine if variable sequences (spacers) between conserved positions in a sequence motif or pattern share a consensus structure, three-dimensional structures containing PROSITE patterns with spacers of fixed length greater than three residues were analyzed. Structural similarities of a given pattern were evaluated by computing the backbone phi, psi and side-chain chi1 dihedral order parameters. The exact bias information in analyzing the conformational variability of the patterns was taken into account by introducing a new parameter, the bias coefficient, which describes the number and distribution of residue types found at each position of a pattern in the structures. The results of the analyses show that backbone conformational heterogeneity at a given position in a sequence motif does not necessarily correlate with the residue-type variability at that position, and the long spacer region can adopt a well-defined backbone conformation, in addition to the conserved residues. Furthermore, a PROSITE pattern may be redefined to yield two or more "refined" regular expressions, each corresponding to a distinct backbone conformation. A way in which the observed structural consensus in a pattern may be employed to improve the accuracy of function prediction from sequence is suggested.
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Affiliation(s)
- K Y Lin
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan, 11529
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40
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Tillett ML, Blackledge MJ, Derrick JP, Lian LY, Norwood TJ. Overall rotational diffusion and internal mobility in domain II of protein G from Streptococcus determined from 15N relaxation data. Protein Sci 2000; 9:1210-6. [PMID: 10892813 PMCID: PMC2144651 DOI: 10.1110/ps.9.6.1210] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The backbone dynamics and overall tumbling of protein G have been investigated using 15N relaxation. Comparison of measured R2/R1 relaxation rate ratios with known three-dimensional coordinates of the protein show that the rotational diffusion tensor is significantly asymmetric, exhibiting a prolate axial symmetry. Extensive Monte Carlo simulations have been used to estimate the uncertainty due to experimental error in the relaxation rates to be D(parallel)/D(perpendicular) = 1.68 +/- 0.08, while the dispersion in the NMR ensemble leads to a variation of D(parallel)/D(perpendicular) = 1.65 +/- 0.03. Incorporation of this tensorial description into a Lipari-Szabo type analysis of internal motion has allowed us to accurately describe the local dynamics of the molecule. This analysis differs from an earlier study where the overall rotational diffusion was described by a spherical top. In this previous analysis, exchange parameters were fitted to many of the residues in the alpha helix. This was interpreted as reflecting a small motion of the alpha helix with respect to the beta sheet. We propose that the differential relaxation properties of this helix compared to the beta sheet are due to the near-orthogonality of the NH vectors in the two structural motifs with respect to the unique axis of the diffusion tensor. Our analysis shows that when anisotropic rotational diffusion is taken into account NH vectors in these structural motifs appear to be equally rigid. This study underlines the importance of a correct description of the rotational diffusion tensor if internal motion is to be accurately investigated.
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Affiliation(s)
- M L Tillett
- Biological NMR Centre, Department of Biochemistry, Leicester University, United Kingdom
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41
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42
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Sutcliffe MJ, Smeeton AH, Wo ZG, Oswald RE. Molecular modeling of ligand-gated ion channels. Methods Enzymol 1998; 293:589-620. [PMID: 9711630 DOI: 10.1016/s0076-6879(98)93035-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
MESH Headings
- Amino Acid Sequence
- Animals
- Binding Sites
- Cell Membrane/physiology
- Cell Membrane/ultrastructure
- Computer Graphics
- Conserved Sequence
- Ion Channel Gating
- Ion Channels/chemistry
- Ion Channels/physiology
- Ligands
- Models, Molecular
- Models, Structural
- Molecular Sequence Data
- Peptide Fragments/chemistry
- Protein Conformation
- Protein Structure, Secondary
- Receptors, GABA/chemistry
- Receptors, GABA/physiology
- Receptors, N-Methyl-D-Aspartate/chemistry
- Receptors, Neurotransmitter/chemistry
- Receptors, Neurotransmitter/physiology
- Receptors, Nicotinic/chemistry
- Receptors, Nicotinic/physiology
- Sequence Alignment
- Sequence Homology, Amino Acid
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Affiliation(s)
- M J Sutcliffe
- Department of Chemistry, University of Leicester, United Kingdom
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43
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Abstract
The analysis of internal motion in ensembles of flexible molecules in coordinate space requires the removal of overall motion by a least-squares fitting procedure of the Cartesian coordinates. It has been demonstrated that the choice of the atom set used for fitting influences the picture of the internal motion of BPTI. We have performed essential dynamics analyses of a 1 ns molecular dynamics trajectory of the single-stranded DNA-binding protein from the Pf3 phage using either all alpha-carbon atoms or the least mobile ones for fitting the trajectory prior to the analysis. We found that covariances of atoms separated by long distances were significantly reduced in the latter case; the overall overlap of essential spaces was still high. In the second part we present a method that does not introduce and bias caused by overall motion: principal component analysis in distance space. Non-trivial dynamic cross-correlations were preserved in distance space, which answers the question posed in the title in the affirmative. However, cross-correlations were throughout smaller than those detected by standard essential dynamics analyses.
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Affiliation(s)
- R Abseher
- European Molecular Biology Laboratory, Meyerhofstrasse 1 69117 Heidelberg, Germany
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44
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Smith G, Modi S, Pillai I, Lian LY, Sutcliffe MJ, Pritchard MP, Friedberg T, Roberts GC, Wolf CR. Determinants of the substrate specificity of human cytochrome P-450 CYP2D6: design and construction of a mutant with testosterone hydroxylase activity. Biochem J 1998; 331 ( Pt 3):783-92. [PMID: 9560305 PMCID: PMC1219418 DOI: 10.1042/bj3310783] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cytochrome P-450 CYP2D6, human debrisoquine hydroxylase, metabolizes more than 30 prescribed drugs, the vast majority of which are small molecules containing a basic nitrogen atom. In contrast, the similar mouse protein Cyp2d-9 was first characterized as a testosterone 16alpha-hydroxylase. No common substrates have been reported for the two enzymes. Here we investigate the structural basis of this difference in substrate specificity. We have earlier used a combination of NMR data and homology modelling to generate a three-dimensional model of CYP2D6 [Modi, Paine, Sutcliffe, Lian, Primrose, Wolf, C.R. and Roberts (1996) Biochemistry 35, 4541-4550]. We have now generated a homology model of Cyp2d-9 and compared the two models to identify specific amino acid residues that we believe form the substrate-binding site in each protein and therefore influence catalytic selectivity. Although there are many similarities in active site structure, the most notable difference is a phenylalanine residue (Phe-483) in CYP2D6, which in the model is located such that the bulky phenyl ring is positioned across the channel mouth, thus limiting the size of substrate that can access the active site. In Cyp2d-9, the corresponding position is occupied by an isoleucine residue, which imposes fewer steric restraints on the size of substrate that can access the active site. To investigate whether the amino acid residue at this position does indeed influence the catalytic selectivity of these enzymes, site-directed mutagenesis was used to change Phe-483 in CYP2D6 to isoleucine and also to tryptophan. CYP2D6, Cyp2d-9 and both mutant CYP2D6 proteins were co-expressed with NADPH cytochrome P-450 reductase as a functional mono-oxygenase system in Escherichia coli and their relative catalytic activities towards bufuralol and testosterone were determined. All four proteins exhibited catalytic activity towards bufuralol but only Cyp2d-9 catalysed the formation of 16alpha-hydroxytesterone. Uniquely, the CYP2D6F483I mutant acquired the ability to metabolize testosterone to a novel product, which was identified by MS and proton NMR spectroscopy as 15alpha-hydroxytestosterone. NMR spin relaxation experiments were used to measure distances between the haem iron and protons of testosterone bound to the CYP2D6F483I mutant. These experiments demonstrate that very minor modifications to the active site structure of CYP2D6 can have a profound influence on the substrate specificity of the enzyme.
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Affiliation(s)
- G Smith
- Biomedical Research Centre, Ninewells Hospital and Medical School, Dundee DD1 9SY, Scotland, UK
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45
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Kelley LA, Sutcliffe MJ. OLDERADO: on-line database of ensemble representatives and domains. On Line Database of Ensemble Representatives And DOmains. Protein Sci 1997; 6:2628-30. [PMID: 9416612 PMCID: PMC2143626 DOI: 10.1002/pro.5560061215] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
In cases where the structure of a single protein is represented by an ensemble of conformations, there is often a need to determine the common features and to choose a "representative" conformation. This occurs, for example, with structures determined by NMR spectroscopy, analysis of the trajectory from a molecular dynamics simulation, or an ensemble of structures produced by comparative modeling. We reported previously automatic methods for (1) defining the atoms with low spatial variance across an ensemble (i.e., the "core" atoms) and the domains in which these atoms lie, and (2) clustering an ensemble into conformationally related subfamilies. To extend the utility of these methods, we have developed a freely available server on the World Wide Web at http:/(/)neon.chem.le.ac.uk/olderado/. This (1) contains an automatically generated database of representative structures, core atoms, and domains determined for 449 ensembles of NMR-derived protein structures in the Protein Data Bank (PDB) in May 1997, and (2) allows the user to upload a PDB-formatted file containing the coordinates of an ensemble of structures. The server returns in real time: (1) information on the residues constituting domains: (2) the structures that constitute each conformational subfamily; and (3) an interactive java-based three-dimensional viewer to visualise the domains and clusters. Such information is useful, for example, when selecting conformations to be used in comparative modeling and when choosing parts of structures to be used in molecular replacement. Here we describe the OLDERADO server.
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Affiliation(s)
- L A Kelley
- Department of Chemistry, University of Leicester, United Kingdom
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