1
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Kosenko M, Onkhonova G, Susloparov I, Ryzhikov A. SARS-CoV-2 proteins structural studies using synchrotron radiation. Biophys Rev 2023; 15:1185-1194. [PMID: 37974992 PMCID: PMC10643813 DOI: 10.1007/s12551-023-01153-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Accepted: 09/20/2023] [Indexed: 11/19/2023] Open
Abstract
In the process of the development of structural biology, both the size and the complexity of the determined macromolecular structures have grown significantly. As a result, the range of application areas for the results of structural studies of biological macromolecules has expanded. Significant progress in the development of structural biology methods has been largely achieved through the use of synchrotron radiation. Modern sources of synchrotron radiation allow to conduct high-performance structural studies with high temporal and spatial resolution. Thus, modern techniques make it possible to obtain not only static structures, but also to study dynamic processes, which play a key role in understanding biological mechanisms. One of the key directions in the development of structural research is the drug design based on the structures of biomolecules. Synchrotron radiation offers insights into the three-dimensional time-resolved structure of individual viral proteins and their complexes at atomic resolution. The rapid and accurate determination of protein structures is crucial for understanding viral pathogenicity and designing targeted therapeutics. Through the application of experimental techniques, including X-ray crystallography and small-angle X-ray scattering (SAXS), it is possible to elucidate the structural details of SARS-CoV-2 virion containing 4 structural, 16 nonstructural proteins (nsp), and several accessory proteins. The most studied potential targets for vaccines and drugs are the structural spike (S) protein, which is responsible for entering the host cell, as well as nonstructural proteins essential for replication and transcription, such as main protease (Mpro), papain-like protease (PLpro), and RNA-dependent RNA polymerase (RdRp). This article provides a brief overview of structural analysis techniques, with focus on synchrotron radiation-based methods applied to the analysis of SARS-CoV-2 proteins.
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Affiliation(s)
- Maksim Kosenko
- Federal Budgetary Research Institution State Research Center of Virology and Biotechnology “Vector” Rospotrebnadzor, Koltsovo, 630559 Russia
| | - Galina Onkhonova
- Federal Budgetary Research Institution State Research Center of Virology and Biotechnology “Vector” Rospotrebnadzor, Koltsovo, 630559 Russia
| | - Ivan Susloparov
- Federal Budgetary Research Institution State Research Center of Virology and Biotechnology “Vector” Rospotrebnadzor, Koltsovo, 630559 Russia
| | - Alexander Ryzhikov
- Federal Budgetary Research Institution State Research Center of Virology and Biotechnology “Vector” Rospotrebnadzor, Koltsovo, 630559 Russia
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2
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Mikhailovskii O, Xue Y, Skrynnikov NR. Modeling a unit cell: crystallographic refinement procedure using the biomolecular MD simulation platform Amber. IUCRJ 2022; 9:114-133. [PMID: 35059216 PMCID: PMC8733891 DOI: 10.1107/s2052252521011891] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Accepted: 11/09/2021] [Indexed: 06/14/2023]
Abstract
A procedure has been developed for the refinement of crystallographic protein structures based on the biomolecular simulation program Amber. The procedure constructs a model representing a crystal unit cell, which generally contains multiple protein molecules and is fully hydrated with TIP3P water. Periodic boundary conditions are applied to the cell in order to emulate the crystal lattice. The refinement is conducted in the form of a specially designed short molecular-dynamics run controlled by the Amber ff14SB force field and the maximum-likelihood potential that encodes the structure-factor-based restraints. The new Amber-based refinement procedure has been tested on a set of 84 protein structures. In most cases, the new procedure led to appreciably lower R free values compared with those reported in the original PDB depositions or obtained by means of the industry-standard phenix.refine program. In particular, the new method has the edge in refining low-accuracy scrambled models. It has also been successful in refining a number of molecular-replacement models, including one with an r.m.s.d. of 2.15 Å. In addition, Amber-refined structures consistently show superior MolProbity scores. The new approach offers a highly realistic representation of protein-protein interactions in the crystal, as well as of protein-water interactions. It also offers a realistic representation of protein crystal dynamics (akin to ensemble-refinement schemes). Importantly, the method fully utilizes the information from the available diffraction data, while relying on state-of-the-art molecular-dynamics modeling to assist with those elements of the structure that do not diffract well (for example mobile loops or side chains). Finally, it should be noted that the protocol employs no tunable parameters, and the calculations can be conducted in a matter of several hours on desktop computers equipped with graphical processing units or using a designated web service.
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Affiliation(s)
- Oleg Mikhailovskii
- Laboratory of Biomolecular NMR, St Petersburg State University, St Petersburg 199034, Russian Federation
- Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA
| | - Yi Xue
- School of Life Sciences, Tsinghua University, Beijing 100084, People's Republic of China
- Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing 100084, People's Republic of China
- Tsinghua University-Peking University Joint Center for Life Sciences, Tsinghua University, Beijing 100084, People's Republic of China
| | - Nikolai R Skrynnikov
- Laboratory of Biomolecular NMR, St Petersburg State University, St Petersburg 199034, Russian Federation
- Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA
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3
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Wang J, Gisriel CJ, Reiss K, Huang HL, Armstrong WH, Brudvig GW, Batista VS. Heterogeneous Composition of Oxygen-Evolving Complexes in Crystal Structures of Dark-Adapted Photosystem II. Biochemistry 2021; 60:3374-3384. [PMID: 34714055 DOI: 10.1021/acs.biochem.1c00611] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photosystem II (PSII) is a homodimeric protein complex that catalyzes water oxidation at the oxygen-evolving complex (OEC), a heterocubanoid calcium-tetramanganese cluster. Here, we analyze the omit electron density peaks of the OEC's metal ions in five X-ray free-electron laser PSII structures at resolutions between 2.15 and 1.95 Å. The omit peaks can be described by the total number of electrons and approximated by the variance of electron density distribution when the distributions are spherically symmetric. We show that the number of electrons of metal centers is different in the two OECs of PSII dimers, implying that the oxidation states and/or occupancies of individual metal ions are different in the two monomers. In either case, we find that the two OECs of dark-adapted PSII dimers in crystals are not fully synchronized in the S1 state. Differences in redox states of the OEC in PSII only partially account for the observation that the electron densities integrate to a smaller number of electrons than expected. Differences between the determined and expected relative electron numbers are much larger than the estimated errors, indicating heterogeneity in the OEC composition.
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Affiliation(s)
- Jimin Wang
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8114, United States
| | - Christopher J Gisriel
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Krystle Reiss
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Hao-Li Huang
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - William H Armstrong
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Gary W Brudvig
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8114, United States.,Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Victor S Batista
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
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4
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Pinto GP, Hendrikse NM, Stourac J, Damborsky J, Bednar D. Virtual screening of potential anticancer drugs based on microbial products. Semin Cancer Biol 2021; 86:1207-1217. [PMID: 34298109 DOI: 10.1016/j.semcancer.2021.07.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 07/14/2021] [Accepted: 07/18/2021] [Indexed: 01/20/2023]
Abstract
The development of microbial products for cancer treatment has been in the spotlight in recent years. In order to accelerate the lengthy and expensive drug development process, in silico screening tools are systematically employed, especially during the initial discovery phase. Moreover, considering the steadily increasing number of molecules approved by authorities for commercial use, there is a demand for faster methods to repurpose such drugs. Here we present a review on virtual screening web tools, such as publicly available databases of molecular targets and libraries of ligands, with the aim to facilitate the discovery of potential anticancer drugs based on microbial products. We provide an entry-level step-by-step description of the workflow for virtual screening of microbial metabolites with known protein targets, as well as two practical examples using freely available web tools. The first case presents a virtual screening study of drugs developed from microbial products using Caver Web, a web tool that performs docking along a tunnel. The second case comprises a comparative analysis between a wild type isocitrate dehydrogenase 1 and a mutant that results in cancer, using the recently developed web tool PredictSNPOnco. In summary, this review provides the basic and essential background information necessary for virtual screening experiments, which may accelerate the discovery of novel anticancer drugs.
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Affiliation(s)
- Gaspar P Pinto
- Loschmidt Laboratories, Department of Experimental Biology and RECETOX, Faculty of Science, Masaryk University, Kamenice 5/A13, Brno, 625 00, Czech Republic; International Clinical Research Center, St. Anne's University Hospital Brno, Pekarska 53, Brno, 656 91, Czech Republic
| | - Natalie M Hendrikse
- Loschmidt Laboratories, Department of Experimental Biology and RECETOX, Faculty of Science, Masaryk University, Kamenice 5/A13, Brno, 625 00, Czech Republic
| | - Jan Stourac
- Loschmidt Laboratories, Department of Experimental Biology and RECETOX, Faculty of Science, Masaryk University, Kamenice 5/A13, Brno, 625 00, Czech Republic; International Clinical Research Center, St. Anne's University Hospital Brno, Pekarska 53, Brno, 656 91, Czech Republic
| | - Jiri Damborsky
- Loschmidt Laboratories, Department of Experimental Biology and RECETOX, Faculty of Science, Masaryk University, Kamenice 5/A13, Brno, 625 00, Czech Republic; International Clinical Research Center, St. Anne's University Hospital Brno, Pekarska 53, Brno, 656 91, Czech Republic
| | - David Bednar
- Loschmidt Laboratories, Department of Experimental Biology and RECETOX, Faculty of Science, Masaryk University, Kamenice 5/A13, Brno, 625 00, Czech Republic; International Clinical Research Center, St. Anne's University Hospital Brno, Pekarska 53, Brno, 656 91, Czech Republic.
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5
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Zhang C, Recacha R, Ruddock LW, Moilanen A. Efficient soluble production of folded cat allergen Fel d 1 in Escherichia coli. Protein Expr Purif 2020; 180:105809. [PMID: 33338588 DOI: 10.1016/j.pep.2020.105809] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Revised: 12/10/2020] [Accepted: 12/11/2020] [Indexed: 10/22/2022]
Abstract
The major cat allergen Fel d 1 is one of the most common and potent causes of animal related allergy. Medical treatment of cat allergy has relied on immunotherapy carried out with cat dander extract. This approach has been problematic, mainly due to inconsistent levels of the major allergen in the produced extracts. Recombinant DNA technology has been proposed as an alternative method to produce more consistent pharmaceuticals for immunotherapy and diagnostics of allergy. Current approaches to produce recombinant Fel d 1 (recFel d 1) in the cytoplasm of Escherichia coli have however resulted in protein folding deficiencies and insoluble inclusion body formation, requiring elaborate in vitro processing to acquire folded material. In this study, we introduce an efficient method for cytoplasmic production of recFel d 1 that utilizes eukaryotic folding factors to aid recFel d 1 to fold and be produced in the soluble fraction of E. coli. The solubly expressed recFel d 1 is shown by biophysical in vitro experiments to contain structural disulfides, is extremely stable, and has a sensitivity for methionine sulfoxidation. The latter is discussed in the context of functional relevance.
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Affiliation(s)
- Chi Zhang
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Aapistie 7, 90220, Oulu, Finland.
| | - Rosario Recacha
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Aapistie 7, 90220, Oulu, Finland.
| | - Lloyd W Ruddock
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Aapistie 7, 90220, Oulu, Finland.
| | - Antti Moilanen
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Aapistie 7, 90220, Oulu, Finland.
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6
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Wang J, Brudvig GW, Batista VS, Moore PB. On the relationship between cumulative correlation coefficients and the quality of crystallographic data sets. Protein Sci 2017; 26:2410-2416. [DOI: 10.1002/pro.3314] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 09/26/2017] [Accepted: 09/27/2017] [Indexed: 02/03/2023]
Affiliation(s)
- Jimin Wang
- Department of Molecular Biophysics and BiochemistryYale UniversityNew Haven Connecticut06520‐8114
| | - Gary W. Brudvig
- Department of Molecular Biophysics and BiochemistryYale UniversityNew Haven Connecticut06520‐8114
- Department of ChemistryYale UniversityNew Haven Connecticut06520‐8107
| | - Victor S. Batista
- Department of ChemistryYale UniversityNew Haven Connecticut06520‐8107
| | - Peter B. Moore
- Department of Molecular Biophysics and BiochemistryYale UniversityNew Haven Connecticut06520‐8114
- Department of ChemistryYale UniversityNew Haven Connecticut06520‐8107
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7
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Wang J. Determination of chemical identity and occupancy from experimental density maps. Protein Sci 2017; 27:411-420. [PMID: 29027293 DOI: 10.1002/pro.3325] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 10/11/2017] [Accepted: 10/11/2017] [Indexed: 12/13/2022]
Abstract
Three basic electronic properties of molecules, electron density (ED), charge density (CD), and electrostatic potentials (ESP), are dependent on both atomic mobility and occupancy of components in the molecules. Small protein subunits may bind large macromolecular complexes with a reduced occupancy or an increased atomic mobility or both due to affinity-based functional regulation, and so may substrates, products, cofactors, ions or solvent molecule to the active sites of enzymes. A quantitative theory is presented in this study that describes the dependence of atomic functions on atomic B-factor in Fourier transforms of the corresponding maps. An application of this theory is described to an experimental ED map at 1.73-Å resolution, and to an experimental CD map at 2.2-Å resolution. All the three density functions are linearly proportional to occupancy when the structure factor F(000) term of Fourier transforms of experimental density maps is included. Upon application of this theory to both experimental CD and ESP maps recently reported for photosystem II-light harvesting complex II supercomplex at 3.2-Å resolution, the occupancy of two extrinsic protein subunits PsbQ and PsbP is determined to be 20.4 ± 0.2%, and the negative mean ESP value of vitreous ice displaced by the supercomplex on electron scattering path is estimated to be 3% of the mean ESP value of protein α-helices.
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Affiliation(s)
- Jimin Wang
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, 06520
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8
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Wang J, Askerka M, Brudvig GW, Batista VS. Insights into Photosystem II from Isomorphous Difference Fourier Maps of Femtosecond X-ray Diffraction Data and Quantum Mechanics/Molecular Mechanics Structural Models. ACS ENERGY LETTERS 2017; 2:397-407. [PMID: 28217747 PMCID: PMC5307371 DOI: 10.1021/acsenergylett.6b00626] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 01/12/2017] [Indexed: 05/30/2023]
Abstract
Understanding structure-function relations in photosystem II (PSII) is important for the development of biomimetic photocatalytic systems. X-ray crystallography, computational modeling, and spectroscopy have played central roles in elucidating the structure and function of PSII. Recent breakthroughs in femtosecond X-ray crystallography offer the possibility of collecting diffraction data from the X-ray free electron laser (XFEL) before radiation damage of the sample, thereby overcoming the main challenge of conventional X-ray diffraction methods. However, the interpretation of XFEL data from PSII intermediates is challenging because of the issues regarding data-processing, uncertainty on the precise positions of light oxygen atoms next to heavy metal centers, and different kinetics of the S-state transition in microcrystals compared to solution. Here, we summarize recent advances and outstanding challenges in PSII structure-function determination with emphasis on the implementation of quantum mechanics/molecular mechanics techniques combined with isomorphous difference Fourier maps, direct methods, and high-resolution spectroscopy.
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Affiliation(s)
- Jimin Wang
- Department
of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8114, United States
| | - Mikhail Askerka
- Department
of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Gary W. Brudvig
- Department
of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Victor S. Batista
- Department
of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
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9
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Abstract
Diffraction data acquisition is the final experimental stage of the crystal structure analysis. All subsequent steps involve mainly computer calculations. Optimally measured and accurate data make the structure solution and refinement easier and lead to more faithful interpretation of the final models. Here, the important factors in data collection from macromolecular crystals are discussed and strategies appropriate for various applications, such as molecular replacement, anomalous phasing, and atomic-resolution refinement are presented. Criteria useful for judging the diffraction data quality are also discussed.
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Affiliation(s)
- Zbigniew Dauter
- Synchrotron Radiation Research Section, MCL, National Cancer Institute, Argonne National Laboratory, Argonne, IL, 60439, USA.
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10
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Abstract
Diffraction data acquisition is the final experimental stage of the crystal structure analysis. All subsequent steps involve mainly computer calculations. Optimally measured and accurate data make the structure solution and refinement easier and lead to more faithful interpretation of the final models. Here, the important factors in data collection from macromolecular crystals are discussed and strategies appropriate for various applications, such as molecular replacement, anomalous phasing, and atomic-resolution refinement are presented. Criteria useful for judging the diffraction data quality are also discussed.
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11
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Wang J. Oxygen additions in serial femtosecond crystallographic protein structures. Protein Sci 2016; 25:1797-802. [PMID: 27438534 DOI: 10.1002/pro.2987] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 07/19/2016] [Indexed: 11/09/2022]
Abstract
In principle, serial femtosecond crystallography (SFX) could yield data sets that are completely free of the effects caused by slow, radiation-induced chemical reactions, for example, oxygen additions, responsible for radiation damage. However, experimental evidence is presented here that SFX data sets obtained by techniques that expose different parts of the same specimen to single pulses of radiation do not have this property, even if the specimen in question is frozen. The diffraction image of each such crystal obtained with the first pulse of radiation is certain to represent the structure of a protein that has not been modified chemically, but all of the images obtained subsequently from the same crystal will represent structures that have been modified to a lesser or greater extent by oxygen additions because of the rapid diffusion of oxygenic free radicals through the specimen. The higher the level of oxygen additions a crystal suffers during data collection, the poorer the statistical quality of data set obtained from it will, and the higher the free R-factors of the resulting structural model.
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Affiliation(s)
- Jimin Wang
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, 06520.
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12
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Carugo O, Djinović-Carugo K. Criteria to Extract High-Quality Protein Data Bank Subsets for Structure Users. Methods Mol Biol 2016; 1415:139-152. [PMID: 27115631 DOI: 10.1007/978-1-4939-3572-7_7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
It is often necessary to build subsets of the Protein Data Bank to extract structural trends and average values. For this purpose it is mandatory that the subsets are non-redundant and of high quality. The first problem can be solved relatively easily at the sequence level or at the structural level. The second, on the contrary, needs special attention. It is not sufficient, in fact, to consider the crystallographic resolution and other feature must be taken into account: the absence of strings of residues from the electron density maps and from the files deposited in the Protein Data Bank; the B-factor values; the appropriate validation of the structural models; the quality of the electron density maps, which is not uniform; and the temperature of the diffraction experiments. More stringent criteria produce smaller subsets, which can be enlarged with more tolerant selection criteria. The incessant growth of the Protein Data Bank and especially of the number of high-resolution structures is allowing the use of more stringent selection criteria, with a consequent improvement of the quality of the subsets of the Protein Data Bank.
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Affiliation(s)
- Oliviero Carugo
- Chemistry Department, University of Pavia, Pavia, Italy.
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, Vienna University, Campus Vienna Biocenter 5, 1030, Vienna, Austria.
| | - Kristina Djinović-Carugo
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, Vienna University, Campus Vienna Biocenter 5, 1030, Vienna, Austria
- Department of Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia
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13
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Wang J. Comment on "Crystal structures of translocator protein (TSPO) and mutant mimic of a human polymorphism". Science 2015; 350:519. [PMID: 26516276 DOI: 10.1126/science.aab1432] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 09/29/2015] [Indexed: 01/17/2023]
Abstract
Li et al. (Reports, 30 January, p. 555) reported on a crystal structure for a translocator protein (TSPO) from Rhodobacter sphaeroides in which some of the electron density is modeled as a porphyrin. The analysis of the x-ray data discussed here suggests that this assignment is incorrect.
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Affiliation(s)
- Jimin Wang
- Department of Molecular Biophysics and Biochemistry, Yale University, 266 Whitney Avenue, New Haven, CT 06520, USA
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14
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Li F, Liu J, Zheng Y, Garavito RM, Ferguson-Miller S. Response to Comment on "Crystal structures of translocator protein (TSPO) and mutant mimic of a human polymorphism". Science 2015; 350:519. [PMID: 26516277 DOI: 10.1126/science.aab2595] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 09/29/2015] [Indexed: 12/15/2022]
Abstract
Wang comments that the diffraction data for the structure of the A139T mutant of translocator protein TSPO from Rhodobacter sphaeroides should be used to 1.65 instead of 1.8 angstroms and that the density interpreted as porphyrin and monoolein is better fitted as polyethylene glycol. Although different practices of data processing exist, in this case they do not substantially influence the final map. Additional data are presented supporting the fit of a porphyrin and monooleins.
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Affiliation(s)
- Fei Li
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Jian Liu
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Yi Zheng
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - R Michael Garavito
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Shelagh Ferguson-Miller
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA.
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15
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Karplus PA, Diederichs K. Assessing and maximizing data quality in macromolecular crystallography. Curr Opin Struct Biol 2015. [PMID: 26209821 DOI: 10.1016/j.sbi.2015.07.003] [Citation(s) in RCA: 166] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The quality of macromolecular crystal structures depends, in part, on the quality and quantity of the data used to produce them. Here, we review recent shifts in our understanding of how to use data quality indicators to select a high resolution cutoff that leads to the best model, and of the potential to greatly increase data quality through the merging of multiple measurements from multiple passes of single crystals or from multiple crystals. Key factors supporting this shift are the introduction of more robust correlation coefficient based indicators of the precision of merged data sets as well as the recognition of the substantial useful information present in extensive amounts of data once considered too weak to be of value.
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Affiliation(s)
- P Andrew Karplus
- Department of Biochemistry & Biophysics, Oregon State University, Corvallis, OR 97331, USA.
| | - Kay Diederichs
- University of Konstanz, Faculty of Biology, Box 647, D-78457 Konstanz, Germany.
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16
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Chellapa GD, Rose GD. On interpretation of protein X-ray structures: Planarity of the peptide unit. Proteins 2015; 83:1687-92. [PMID: 26148341 DOI: 10.1002/prot.24854] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Revised: 06/26/2015] [Accepted: 06/30/2015] [Indexed: 11/09/2022]
Abstract
Pauling's mastery of peptide stereochemistry-based on small molecule crystal structures and the theory of chemical bonding-led to his realization that the peptide unit is planar and then to the Pauling-Corey-Branson model of the α-helix. Similarly, contemporary protein structure refinement is based on experimentally determined diffraction data together with stereochemical restraints. However, even an X-ray structure at ultra-high resolution is still an under-determined model in which the linkage among refinement parameters is complex. Consequently, restrictions imposed on any given parameter can affect the entire structure. Here, we examine recent studies of high resolution protein X-ray structures, where substantial distortions of the peptide plane are found to be commonplace. Planarity is assessed by the ω-angle, a dihedral angle determined by the peptide bond (C-N) and its flanking covalent neighbors; for an ideally planar trans peptide, ω = 180°. By using a freely available refinement package, Phenix [Afonine et al. (2012) Acta Cryst. D, 68:352-367], we demonstrate that tightening default restrictions on the ω-angle can significantly reduce apparent deviations from peptide unit planarity without consequent reduction in reported evaluation metrics (e.g., R-factors). To be clear, our result does not show that substantial non-planarity is absent, only that an equivalent alternative model is possible. Resolving this disparity will ultimately require improved understanding of the deformation energy. Meanwhile, we urge inclusion of ω-angle statistics in new structure reports in order to focus critical attention on the usual practice of assigning default values to ω-angle constraints during structure refinement.
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Affiliation(s)
- George D Chellapa
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, 21218
| | - George D Rose
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, 21218
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17
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Matthews BW. Which of the 100,000 structures in the protein data bank are reliable? Protein Sci 2015; 24:589-91. [DOI: 10.1002/pro.2662] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 02/06/2015] [Indexed: 11/09/2022]
Affiliation(s)
- Brian W. Matthews
- Institute of Molecular Biology and Department of Physics; University of Oregon; Eugene Oregon 97403
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