51
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Schreiber A, Schiller SM. Nanobiotechnology of protein-based compartments: steps toward nanofactories. BIOINSPIRED BIOMIMETIC AND NANOBIOMATERIALS 2013. [DOI: 10.1680/bbn.13.00008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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52
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Mizuta T, Ando K, Uemura T, Kawata Y, Mizobata T. Probing the dynamic process of encapsulation in Escherichia coli GroEL. PLoS One 2013; 8:e78135. [PMID: 24205127 PMCID: PMC3813556 DOI: 10.1371/journal.pone.0078135] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Accepted: 09/16/2013] [Indexed: 11/24/2022] Open
Abstract
Kinetic analyses of GroE-assisted folding provide a dynamic sequence of molecular events that underlie chaperonin function. We used stopped-flow analysis of various fluorescent GroEL mutants to obtain details regarding the sequence of events that transpire immediately after ATP binding to GroEL and GroEL with prebound unfolded proteins. Characterization of GroEL CP86, a circularly permuted GroEL with the polypeptide ends relocated to the vicinity of the ATP binding site, showed that GroES binding and protection of unfolded protein from solution is achieved surprisingly early in the functional cycle, and in spite of greatly reduced apical domain movement. Analysis of fluorescent GroEL SR-1 and GroEL D398A variants suggested that among other factors, the presence of two GroEL rings and a specific conformational rearrangement of Helix M in GroEL contribute significantly to the rapid release of unfolded protein from the GroEL apical domain.
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Affiliation(s)
- Toshifumi Mizuta
- Department of Biotechnology, Graduate School of Engineering, Tottori, Japan
| | - Kasumi Ando
- Department of Biotechnology, Graduate School of Engineering, Tottori, Japan
| | - Tatsuya Uemura
- Department of Biomedical Science, Graduate School of Medical Sciences, Tottori University, Tottori, Japan
| | - Yasushi Kawata
- Department of Biotechnology, Graduate School of Engineering, Tottori, Japan
- Department of Biomedical Science, Graduate School of Medical Sciences, Tottori University, Tottori, Japan
| | - Tomohiro Mizobata
- Department of Biotechnology, Graduate School of Engineering, Tottori, Japan
- Department of Biomedical Science, Graduate School of Medical Sciences, Tottori University, Tottori, Japan
- * E-mail:
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53
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Cossio P, Hummer G. Bayesian analysis of individual electron microscopy images: towards structures of dynamic and heterogeneous biomolecular assemblies. J Struct Biol 2013; 184:427-37. [PMID: 24161733 DOI: 10.1016/j.jsb.2013.10.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 10/05/2013] [Accepted: 10/09/2013] [Indexed: 10/26/2022]
Abstract
We develop a method to extract structural information from electron microscopy (EM) images of dynamic and heterogeneous molecular assemblies. To overcome the challenge of disorder in the imaged structures, we analyze each image individually, avoiding information loss through clustering or averaging. The Bayesian inference of EM (BioEM) method uses a likelihood-based probabilistic measure to quantify the consistency between each EM image and given structural models. The likelihood function accounts for uncertainties in the molecular position and orientation, variations in the relative intensities and noise in the experimental images. The BioEM formalism is physically intuitive and mathematically simple. We show that for experimental GroEL images, BioEM correctly identifies structures according to the functional state. The top-ranked structure is the corresponding X-ray crystal structure, followed by an EM structure generated previously from a superset of the EM images used here. To analyze EM images of highly flexible molecules, we propose an ensemble refinement procedure, and validate it with synthetic EM maps of the ESCRT-I-II supercomplex. Both the size of the ensemble and its structural members are identified correctly. BioEM offers an alternative to 3D-reconstruction methods, extracting accurate population distributions for highly flexible structures and their assemblies. We discuss limitations of the method, and possible applications beyond ensemble refinement, including the cross-validation and unbiased post-assessment of model structures, and the structural characterization of systems where traditional approaches fail. Overall, our results suggest that the BioEM framework can be used to analyze EM images of both ordered and disordered molecular systems.
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Affiliation(s)
- Pilar Cossio
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany; Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0520, USA
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54
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gEMfitter: a highly parallel FFT-based 3D density fitting tool with GPU texture memory acceleration. J Struct Biol 2013; 184:348-54. [PMID: 24060989 DOI: 10.1016/j.jsb.2013.09.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2013] [Revised: 09/06/2013] [Accepted: 09/10/2013] [Indexed: 11/24/2022]
Abstract
Fitting high resolution protein structures into low resolution cryo-electron microscopy (cryo-EM) density maps is an important technique for modeling the atomic structures of very large macromolecular assemblies. This article presents "gEMfitter", a highly parallel fast Fourier transform (FFT) EM density fitting program which can exploit the special hardware properties of modern graphics processor units (GPUs) to accelerate both the translational and rotational parts of the correlation search. In particular, by using the GPU's special texture memory hardware to rotate 3D voxel grids, the cost of rotating large 3D density maps is almost completely eliminated. Compared to performing 3D correlations on one core of a contemporary central processor unit (CPU), running gEMfitter on a modern GPU gives up to 26-fold speed-up. Furthermore, using our parallel processing framework, this speed-up increases linearly with the number of CPUs or GPUs used. Thus, it is now possible to use routinely more robust but more expensive 3D correlation techniques. When tested on low resolution experimental cryo-EM data for the GroEL-GroES complex, we demonstrate the satisfactory fitting results that may be achieved by using a locally normalised cross-correlation with a Laplacian pre-filter, while still being up to three orders of magnitude faster than the well-known COLORES program.
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55
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Abstract
Noncovalently "stacked" tetramethylrhodamine (TMR) dimers have been used to both report and perturb the allosteric equilibrium in GroEL. A GroEL mutant (K242C) has been labeled with TMR, close to the peptide-binding site in the apical domain, such that TMR molecules on adjacent subunits are able to form dimers in the T allosteric state. Addition of ATP induces the transition to the R state and the separation of the peptide-binding sites, with concomitant unstacking of the TMR dimers. A statistical analysis of the spectra allowed us to compute the number and orientation of TMR dimers per ring as a function of the average number of TMR molecules per ring. The TMR dimers thus serve as quantitative reporter of the allosteric state of the system. The TMR dimers also serve as a surrogate for substrate protein, substituting in a more homogeneous, quantifiable manner for the heterogeneous intersubunit, intraring, noncovalent cross-links provided by the substrate protein. The characteristic stimulation of the ATPase activity by substrate protein is also mimicked by the TMR dimers. Using an expanded version of the nested cooperativity model, we determine values for the free energy of the TT to TR and TR to RR allosteric equilibria to be 27 ± 11 and 46 ± 2 kJ/mol, respectively. The free energy of unstacking of the TMR dimers was estimated at 2.6 ± 1.0 kJ/mol dimer. These results demonstrate that GroEL can perform work during the T to R transition, supporting the iterative annealing model of chaperonin function.
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56
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Colaco CA, Bailey CR, Walker KB, Keeble J. Heat shock proteins: stimulators of innate and acquired immunity. BIOMED RESEARCH INTERNATIONAL 2013; 2013:461230. [PMID: 23762847 PMCID: PMC3677648 DOI: 10.1155/2013/461230] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Accepted: 05/09/2013] [Indexed: 12/26/2022]
Abstract
Adjuvants were reintroduced into modern immunology as the dirty little secret of immunologists by Janeway and thus began the molecular definition of innate immunity. It is now clear that the binding of pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors (PRRs) on antigen presenting cells (APCs) activates the innate immune response and provides the host with a rapid mechanism for detecting infection by pathogens and initiates adaptive immunity. Ironically, in addition to advancing the basic science of immunology, Janeway's revelation on induction of the adaptive system has also spurred an era of rational vaccine design that exploits PRRs. Thus, defined PAMPs that bind to known PRRs are being specifically coupled to antigens to improve their immunogenicity. However, while PAMPs efficiently activate the innate immune response, they do not mediate the capture of antigen that is required to elicit the specific responses of the acquired immune system. Heat shock proteins (HSPs) are molecular chaperones that are found complexed to client polypeptides and have been studied as potential cancer vaccines. In addition to binding PRRs and activating the innate immune response, HSPs have been shown to both induce the maturation of APCs and provide chaperoned polypeptides for specific triggering of the acquired immune response.
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Affiliation(s)
- Camilo A. Colaco
- ImmunoBiology Limited, Babraham Research Campus, Cambridge CB22 3AT, UK
| | | | | | - James Keeble
- NIBSC, Blanche Lane, South Mimms, Potters Bar EN6 3QG, UK
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57
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Zhang K, Wang L, Liu Y, Chan KY, Pang X, Schulten K, Dong Z, Sun F. Flexible interwoven termini determine the thermal stability of thermosomes. Protein Cell 2013; 4:432-44. [PMID: 23709365 DOI: 10.1007/s13238-013-3026-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2013] [Accepted: 04/26/2013] [Indexed: 01/27/2023] Open
Abstract
Group II chaperonins, which assemble as double-ring complexes, assist in the refolding of nascent peptides or denatured proteins in an ATP-dependent manner. The molecular mechanism of group II chaperonin assembly and thermal stability is yet to be elucidated. Here, we selected the group II chaperonins (cpn-α and cpn-β), also called thermosomes, from Acidianus tengchongensis and investigated their assembly and thermal stability. We found that the binding of ATP or its analogs contributed to the successful assembly of thermosomes and enhanced their thermal stabilities. Cpn-β is more thermally stable than cpn-α, while the thermal stability of the hetero thermosome cpn-αβ is intermediate. Cryo-electron microscopy reconstructions of cpn-α and cpn-β revealed the interwoven densities of their non-conserved flexible N/C-termini around the equatorial planes. The deletion or swapping of their termini and pH-dependent thermal stability assays revealed the key role of the termini electrostatic interactions in the assembly and thermal stability of the thermosomes.
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Affiliation(s)
- Kai Zhang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
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58
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Henderson B, Fares MA, Lund PA. Chaperonin 60: a paradoxical, evolutionarily conserved protein family with multiple moonlighting functions. Biol Rev Camb Philos Soc 2013; 88:955-87. [DOI: 10.1111/brv.12037] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Revised: 02/20/2013] [Accepted: 03/04/2013] [Indexed: 02/07/2023]
Affiliation(s)
- Brian Henderson
- Department of Microbial Diseases, UCL-Eastman Dental Institute; University College London; London WC1X 8LD U.K
| | - Mario A. Fares
- Department of Genetics; University of Dublin, Trinity College Dublin; Dublin 2 Ireland
- Department of Abiotic Stress; Instituto de Biologia Molecular y Celular de Plantas, Consejo Superior de Investigaciones Cientificas (CSIC-UPV); Valencia 46022 Spain
| | - Peter A. Lund
- School of Biosciences; University of Birmingham; Birmingham B15 2TT U.K
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59
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Zhang Q, Chen J, Kuwajima K, Zhang HM, Xian F, Young NL, Marshall AG. Nucleotide-induced conformational changes of tetradecameric GroEL mapped by H/D exchange monitored by FT-ICR mass spectrometry. Sci Rep 2013; 3:1247. [PMID: 23409238 PMCID: PMC3570780 DOI: 10.1038/srep01247] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Accepted: 11/06/2012] [Indexed: 11/29/2022] Open
Abstract
Here we employ hydrogen/deuterium exchange mass spectrometry (HDX-MS) to access E. coli chaperonin GroEL conformation. The ~800 kDa tetradecameric GroEL plays an essential role in the proper folding of many proteins. Previous studies of the structural dynamics of GroEL upon ATP binding have been inconsistent, showing either minimal or major allosteric changes. Our results, based on the native, non-mutated, protein under physiological conditions in solution demonstrate substantial changes in conformation and/or flexibility upon ATP binding. We capture the pivotal step in its functional cycle by use of a non-hydrolyzable ATP analog, ATPγS, to mimic the ATP-bound GroEL state. Comparison of HDX-MS results for apo GroEL and GroEL-ATPγS enables the characterization of the nucleotide-regulated conformational changes throughout the entire protein with high sequence resolution. The 14-mer GroEL complex is the largest protein assembly yet accessed by HDX-MS, with sequence resolution of segments of as few as five amino acids.
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Affiliation(s)
- Qian Zhang
- Florida State University, Department of Chemistry, Tallahassee, FL 32306, USA
- These authors contributed equally to this work
| | - Jin Chen
- Okazaki Institute for Integrative Bioscience and Institute for Molecular Science, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki 444-8787, Japan
- These authors contributed equally to this work
| | - Kunihiro Kuwajima
- Okazaki Institute for Integrative Bioscience and Institute for Molecular Science, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki 444-8787, Japan
- Department of Functional Molecular Science, School of Physical Sciences, Graduate University for Advanced Studies (Sokendai), 5-1 Higashiyama, Myodaiji, Okazaki 444-8787, Japan
| | - Hui-Min Zhang
- National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, FL 32310, USA
| | - Feng Xian
- National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, FL 32310, USA
| | - Nicolas L. Young
- National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, FL 32310, USA
| | - Alan G. Marshall
- Florida State University, Department of Chemistry, Tallahassee, FL 32306, USA
- National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, FL 32310, USA
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60
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Consensus among multiple approaches as a reliability measure for flexible fitting into cryo-EM data. J Struct Biol 2013; 182:67-77. [PMID: 23416197 DOI: 10.1016/j.jsb.2013.02.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2012] [Revised: 01/29/2013] [Accepted: 02/01/2013] [Indexed: 12/14/2022]
Abstract
Cryo-electron microscopy (cryo-EM) can provide low-resolution density maps of large macromolecular assemblies. As the number of structures deposited in the Protein Data Bank by fitting a high-resolution structure into a low-resolution cryo-EM map is increasing, there is a need to revise the protocols and improve the measures for fitting. A recent study suggested using a combination of multiple automated flexible fitting approaches to improve the interpretation of cryo-EM data. The current work further explores the use of multiple approaches by validating this "consensus" fitting approach and deriving a local reliability measure. Here four different flexible fitting approaches are applied for fitting an initial structure into a simulated density map of known target structure from a dataset of proteins. It is found that the models produced from different approaches often have a consensus in conformation and are also near to the target structure, whereas cases not showing consensus are away from the target. A high correlation is also observed between the RMSF profiles calculated with respect to the average and the target structures, which indicates that the relation between consensus and accuracy can also be extended to a per-residue level. Therefore, the RMSF among the fitted models is proposed as a local reliability measure, which can be used to assess the reliability of the fit at specific regions. Hence, we encourage the community to use consensus flexible fitting with different methods to report on local reliability of the resulting models and improve the interpretation of cryo-EM data.
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61
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Jayasinghe M, Shrestha P, Wu X, Tehver R, Stan G. Weak intra-ring allosteric communications of the archaeal chaperonin thermosome revealed by normal mode analysis. Biophys J 2013; 103:1285-95. [PMID: 22995501 DOI: 10.1016/j.bpj.2012.07.049] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 07/09/2012] [Accepted: 07/13/2012] [Indexed: 12/21/2022] Open
Abstract
Chaperonins are molecular machines that use ATP-driven cycles to assist misfolded substrate proteins to reach the native state. During the functional cycle, these machines adopt distinct nucleotide-dependent conformational states, which reflect large-scale allosteric changes in individual subunits. Distinct allosteric kinetics has been described for the two chaperonin classes. Bacterial (group I) chaperonins, such as GroEL, undergo concerted subunit motions within each ring, whereas archaeal and eukaryotic chaperonins (group II) undergo sequential subunit motions. We study these distinct mechanisms through a comparative normal mode analysis of monomer and double-ring structures of the archaeal chaperonin thermosome and GroEL. We find that thermosome monomers of each type exhibit common low-frequency behavior of normal modes. The observed distinct higher-frequency modes are attributed to functional specialization of these subunit types. The thermosome double-ring structure has larger contribution from higher-frequency modes, as it is found in the GroEL case. We find that long-range intersubunit correlation of amino-acid pairs is weaker in the thermosome ring than in GroEL. Overall, our results indicate that distinct allosteric behavior of the two chaperonin classes originates from different wiring of individual subunits as well as of the intersubunit communications.
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Affiliation(s)
- Manori Jayasinghe
- Department of Chemistry, Northern Kentucky University, Highland Heights, Kentucky, USA
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62
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de Vries SJ, Zacharias M. ATTRACT-EM: a new method for the computational assembly of large molecular machines using cryo-EM maps. PLoS One 2012; 7:e49733. [PMID: 23251350 PMCID: PMC3522670 DOI: 10.1371/journal.pone.0049733] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Accepted: 10/17/2012] [Indexed: 11/23/2022] Open
Abstract
Many of the most important functions in the cell are carried out by proteins organized in large molecular machines. Cryo-electron microscopy (cryo-EM) is increasingly being used to obtain low resolution density maps of these large assemblies. A new method, ATTRACT-EM, for the computational assembly of molecular assemblies from their components has been developed. Based on concepts from the protein-protein docking field, it utilizes cryo-EM density maps to assemble molecular subunits at near atomic detail, starting from millions of initial subunit configurations. The search efficiency was further enhanced by recombining partial solutions, the inclusion of symmetry information, and refinement using a molecular force field. The approach was tested on the GroES-GroEL system, using an experimental cryo-EM map at 23.5 Å resolution, and on several smaller complexes. Inclusion of experimental information on the symmetry of the systems and the application of a new gradient vector matching algorithm allowed the efficient identification of docked assemblies in close agreement with experiment. Application to the GroES-GroEL complex resulted in a top ranked model with a deviation of 4.6 Å (and a 2.8 Å model within the top 10) from the GroES-GroEL crystal structure, a significant improvement over existing methods.
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Affiliation(s)
- Sjoerd J de Vries
- Physik-Department T38, Technische Universität München, Garching, Germany.
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63
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Burger V, Chennubhotla C. Nhs: network-based hierarchical segmentation for cryo-electron microscopy density maps. Biopolymers 2012; 97:732-41. [PMID: 22696408 PMCID: PMC3483038 DOI: 10.1002/bip.22041] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Cryo-electron microscopy (cryo-EM) experiments yield low-resolution (3-30 Å) 3D-density maps of macromolecules. These density maps are segmented to identify structurally distinct proteins, protein domains, and subunits. Such partitioning aids the inference of protein motions and guides fitting of high-resolution atomistic structures. Cryo-EM density map segmentation has traditionally required tedious and subjective manual partitioning or semisupervised computational methods, whereas validation of resulting segmentations has remained an open problem in this field. We introduce a network-based hierarchical segmentation (Nhs) method, that provides a multi-scale partitioning, reflecting local and global clustering, while requiring no user input. This approach models each map as a graph, where map voxels constitute nodes and weighted edges connect neighboring voxels. Nhs initiates Markov diffusion (or random walk) on the weighted graph. As Markov probabilities homogenize through diffusion, an intrinsic segmentation emerges. We validate the segmentations with ground-truth maps based on atomistic models. When implemented on density maps in the 2010 Cryo-EM Modeling Challenge, Nhs efficiently and objectively partitions macromolecules into structurally and functionally relevant subregions at multiple scales.
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Affiliation(s)
- Virginia Burger
- Joint CMU-Pitt Ph.D. Program in Computational Biology, University of Pittsburgh School of Medicine
- Department of Computational and Systems Biology, University of Pittsburgh School of Medicine
| | - Chakra Chennubhotla
- Department of Computational and Systems Biology, University of Pittsburgh School of Medicine
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64
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Baker ML, Baker MR, Hryc CF, Ju T, Chiu W. Gorgon and pathwalking: macromolecular modeling tools for subnanometer resolution density maps. Biopolymers 2012; 97:655-68. [PMID: 22696403 PMCID: PMC3899894 DOI: 10.1002/bip.22065] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The complex interplay of proteins and other molecules, often in the form of large transitory assemblies, are critical to cellular function. Today, X-ray crystallography and electron cryo-microscopy (cryo-EM) are routinely used to image these macromolecular complexes, though often at limited resolutions. Despite the rapidly growing number of macromolecular structures, few tools exist for modeling and annotating structures in the range of 3-10 Å resolution. To address this need, we have developed a number of utilities specifically targeting subnanometer resolution density maps. As part of the 2010 Cryo-EM Modeling Challenge, we demonstrated two of our latest de novo modeling tools, Pathwalking and Gorgon, as well as a tool for secondary structure identification (SSEHunter) and a new rigid-body/flexible fitting tool in Gorgon. In total, we submitted 30 structural models from ten different subnanometer resolution data sets in four of the six challenge categories. Each of our utlities produced accurate structural models and annotations across the various density maps. In the end, the utilities that we present here offer users a robust toolkit for analyzing and modeling protein structure in macromolecular assemblies at non-atomic resolutions.
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Affiliation(s)
- Matthew L Baker
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, National Center for Macromolecular Imaging, Baylor College of Medicine, Houston, TX 77030, USA.
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65
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Wang Z, Schröder GF. Real-space refinement with DireX: from global fitting to side-chain improvements. Biopolymers 2012; 97:687-97. [PMID: 22696405 DOI: 10.1002/bip.22046] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Single-particle cryo-electron microscopy (cryo-EM) has become an important tool to determine the structure of large biomolecules and assemblies thereof. However, the achievable resolution varies considerably over a wide range of about 3.5-20 Å. The interpretation of these intermediate- to low-resolution density maps in terms of atomic models is a big challenge and an area of active research. Here, we present our real-space structure refinement program DireX, which was developed primarily for cryo-EM-derived density maps. The basic principle and its main features are described. DireX employs Deformable Elastic Network (DEN) restraints to reduce overfitting by decreasing the effective number of degrees of freedom used in the refinement. Missing or reduced density due to flexible parts of the protein can lead to artifacts in the structure refinement, which is addressed through the concept of restrained grouped occupancy refinement. Furthermore, we describe the performance of DireX in the 2010 Cryo-EM Modeling Challenge, where we chose six density maps of four different proteins provided by the Modeling Challenge exemplifying typical refinement results at a large resolution range from 3 to 23 Å.
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Affiliation(s)
- Zhe Wang
- Institute of Complex Systems, Forschungszentrum Jülich, Jülich, Germany
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66
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Zhang Q, Bettadapura R, Bajaj C. Macromolecular structure modeling from 3D EM using VolRover 2.0. Biopolymers 2012; 97:709-31. [PMID: 22696407 DOI: 10.1002/bip.22052] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We review tools for structure identification and model-based refinement from three-dimensional electron microscopy implemented in our in-house software package, VOLROVER 2.0. For viral density maps with icosahedral symmetry, we segment the capsid, polymeric, and monomeric subunits using techniques based on automatic symmetry detection and multidomain fast marching. For large biomolecules without symmetry information, we again use our multidomain fast-marching method with manual or fit-based multiseeding to segment meaningful substructures. In either case, we subject the resulting segmented subunit to secondary structure detection when the EM resolution is sufficiently high, and rigid-body structure fitting when the corresponding X-ray structure is available. Secondary structure elements are identified by three techniques: our earlier volume-based and boundary-based skeletonization methods as well as a new method, currently in development, based on solving the grassfire flow equation. For rigid-body fitting, we adapt our earlier fast Fourier-based correlation scheme F2Dock. Our reported segmentation, secondary structure elements identification, and rigid-body fitting techniques, implemented in VOLROVER 2.0 are applied to the PSB 2011 cryo-EM modeling challenge data, and our results are briefly compared to similar results submitted from other research groups. The comparisons show that our techniques are equally capable of segmenting relatively accurate subunits from a viral or protein assembly, and that high segmentation quality leads in turn to higher-quality results of secondary structure elements identification and correlation-based rigid-body fitting. © 2012 Wiley Periodicals, Inc. Biopolymers 97: 709-731, 2012.
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Affiliation(s)
- Qin Zhang
- Institute for Computational Engineering and Sciences, The University of Texas, Austin, TX 78712, USA
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67
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Skjaerven L, Muga A, Reuter N, Martinez A. A dynamic model of long-range conformational adaptations triggered by nucleotide binding in GroEL-GroES. Proteins 2012; 80:2333-46. [PMID: 22576372 DOI: 10.1002/prot.24113] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Revised: 04/26/2012] [Accepted: 05/04/2012] [Indexed: 11/09/2022]
Abstract
The molecular chaperone, GroEL, essential for correct protein folding in E. coli, is composed of 14 identical subunits organized in two interacting rings, each providing a folding chamber for non-native substrate proteins. The oligomeric assembly shows positive cooperativity within each ring and negative cooperativity between the rings. Although it is well known that ATP and long-range allosteric interactions drive the functional cycle of GroEL, an atomic resolution view of how ligand binding modulates conformational adaptations over long distances remains a major challenge. Moreover, little is known on the relation between equilibrium dynamics at physiological temperatures and the allosteric transitions in GroEL. Here we present multiple all-atom molecular dynamics simulations of the GroEL-GroES assemblies at different stages of the functional cycle. Combined with an extensive analysis of the complete set of experimentally available structures, principal component analysis and conformer plots, we provide an explicit evaluation of the accessible conformational space of unliganded GroEL. Our results suggest the presence of pre-existing conformers at the equatorial domain level, and a shift of the conformational ensemble upon ATP-binding. At the inter-ring interface the simulations capture a remarkable offset motion of helix D triggered by ATP-binding to the folding active ring. The reorientation of helix D, previously only observed upon GroES association, correlates with a change of the internal dynamics in the opposite ring. This work contributes to the understanding of the molecular mechanisms in GroEL and highlights the ability of all-atom MD simulations to model long-range structural changes and allosteric events in large systems.
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Affiliation(s)
- Lars Skjaerven
- Department of Biomedicine, University of Bergen, Bergen, Norway.
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Clare DK, Vasishtan D, Stagg S, Quispe J, Farr GW, Topf M, Horwich AL, Saibil HR. ATP-triggered conformational changes delineate substrate-binding and -folding mechanics of the GroEL chaperonin. Cell 2012; 149:113-23. [PMID: 22445172 PMCID: PMC3326522 DOI: 10.1016/j.cell.2012.02.047] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Revised: 10/24/2011] [Accepted: 02/06/2012] [Indexed: 11/24/2022]
Abstract
The chaperonin GroEL assists the folding of nascent or stress-denatured polypeptides by actions of binding and encapsulation. ATP binding initiates a series of conformational changes triggering the association of the cochaperonin GroES, followed by further large movements that eject the substrate polypeptide from hydrophobic binding sites into a GroES-capped, hydrophilic folding chamber. We used cryo-electron microscopy, statistical analysis, and flexible fitting to resolve a set of distinct GroEL-ATP conformations that can be ordered into a trajectory of domain rotation and elevation. The initial conformations are likely to be the ones that capture polypeptide substrate. Then the binding domains extend radially to separate from each other but maintain their binding surfaces facing the cavity, potentially exerting mechanical force upon kinetically trapped, misfolded substrates. The extended conformation also provides a potential docking site for GroES, to trigger the final, 100° domain rotation constituting the “power stroke” that ejects substrate into the folding chamber.
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Affiliation(s)
- Daniel K Clare
- Crystallography and Institute of Structural and Molecular Biology, Birkbeck College, University of London, Malet Street, London WC1E 7HX, UK
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69
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Dynamics, flexibility and ligand-induced conformational changes in biological macromolecules: a computational approach. Future Med Chem 2012; 3:2079-100. [PMID: 22098354 DOI: 10.4155/fmc.11.159] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Biomolecules possess important dynamical properties that enable them to adapt and alternate their conformation as a response to environmental stimuli. Recent advancements in computational resources and methodology allow a higher capability to mimic in vitro conditions and open up the possibility of studying large systems over longer timescales. Here, we describe commonly used computational approaches for studying the dynamic properties of proteins. We review a selected set of simulation studies on ligand-induced changes in the chaperonin GroEL-GroES, a molecular folding machine, maltose-binding protein, a prototypical member of the periplasmic binding proteins, and the bacterial ribosomal A-site, focusing on aminoglycoside antibiotic recognition. We also discuss a recent quantitative reconstruction of the binding process of benzamidine and trypsin. These studies contribute to the understanding and further development of the medicinal regulation of large biomolecular systems.
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70
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Piggot TJ, Sessions RB, Burston SG. Toward a detailed description of the pathways of allosteric communication in the GroEL chaperonin through atomistic simulation. Biochemistry 2012; 51:1707-18. [PMID: 22289022 DOI: 10.1021/bi201237a] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
GroEL, along with its coprotein GroES, is essential for ensuring the correct folding of unfolded or newly synthesized proteins in bacteria. GroEL is a complex, allosteric molecule, composed of two heptameric rings stacked back to back, that undergoes large structural changes during its reaction cycle. These structural changes are driven by the cooperative binding and subsequent hydrolysis of ATP, by GroEL. Despite numerous previous studies, the precise mechanisms of allosteric communication and the associated structural changes remain elusive. In this paper, we describe a series of all-atom, unbiased, molecular dynamics simulations over relatively long (50-100 ns) time scales of a single, isolated GroEL subunit and also a heptameric GroEL ring, in the presence and absence of ATP. Combined with results from a distance restraint-biased simulation of the single ring, the atomistic details of the earliest stages of ATP-driven structural changes within this complex molecule are illuminated. Our results are in broad agreement with previous modeling studies of isolated subunits and with a coarse-grained, forcing simulation of the single ring. These are the first reported all-atom simulations of the GroEL single-ring complex and provide a unique insight into the role of charged residues K80, K277, R284, R285, and E388 at the subunit interface in transmission of the allosteric signal. These simulations also demonstrate the feasibility of performing all-atom simulations of very large systems on sufficiently long time scales on typical high performance computing facilities to show the origins of the earliest events in biologically relevant processes.
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Affiliation(s)
- Thomas J Piggot
- School of Biochemistry, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK
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71
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Finding rigid bodies in protein structures: Application to flexible fitting into cryoEM maps. J Struct Biol 2012; 177:520-31. [DOI: 10.1016/j.jsb.2011.10.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2011] [Revised: 10/22/2011] [Accepted: 10/27/2011] [Indexed: 11/18/2022]
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72
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Hildenbrand ZL, Bernal RA. Chaperonin-Mediated Folding of Viral Proteins. VIRAL MOLECULAR MACHINES 2012; 726:307-24. [DOI: 10.1007/978-1-4614-0980-9_13] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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73
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Tanabe M, Ishida R, Izuhara F, Komatsuda A, Wakui H, Sawada K, Otaka M, Nakamura N, Itoh H. The ATPase activity of molecular chaperone HSP60 is inhibited by immunosuppressant mizoribine. ACTA ACUST UNITED AC 2012. [DOI: 10.4236/ajmb.2012.22010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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74
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Lasker K, Velázquez-Muriel JA, Webb BM, Yang Z, Ferrin TE, Sali A. Macromolecular assembly structures by comparative modeling and electron microscopy. Methods Mol Biol 2012; 857:331-350. [PMID: 22323229 DOI: 10.1007/978-1-61779-588-6_15] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Advances in electron microscopy allow for structure determination of large biological machines at increasingly higher resolutions. A key step in this process is fitting component structures into the electron microscopy-derived density map of their assembly. Comparative modeling can contribute by providing atomic models of the components, via fold assignment, sequence-structure alignment, model building, and model assessment. All four stages of comparative modeling can also benefit from consideration of the density map. In this chapter, we describe numerous types of modeling problems restrained by a density map and available protocols for finding solutions. In particular, we provide detailed instructions for density map-guided modeling using the Integrative Modeling Platform (IMP), MODELLER, and UCSF Chimera.
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Affiliation(s)
- Keren Lasker
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, CA, USA.
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75
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Mitternacht S, Berezovsky IN. Coherent conformational degrees of freedom as a structural basis for allosteric communication. PLoS Comput Biol 2011; 7:e1002301. [PMID: 22174669 PMCID: PMC3234217 DOI: 10.1371/journal.pcbi.1002301] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Accepted: 10/29/2011] [Indexed: 01/10/2023] Open
Abstract
Conformational changes in allosteric regulation can to a large extent be described as motion along one or a few coherent degrees of freedom. The states involved are inherent to the protein, in the sense that they are visited by the protein also in the absence of effector ligands. Previously, we developed the measure binding leverage to find sites where ligand binding can shift the conformational equilibrium of a protein. Binding leverage is calculated for a set of motion vectors representing independent conformational degrees of freedom. In this paper, to analyze allosteric communication between binding sites, we introduce the concept of leverage coupling, based on the assumption that only pairs of sites that couple to the same conformational degrees of freedom can be allosterically connected. We demonstrate how leverage coupling can be used to analyze allosteric communication in a range of enzymes (regulated by both ligand binding and post-translational modifications) and huge molecular machines such as chaperones. Leverage coupling can be calculated for any protein structure to analyze both biological and latent catalytic and regulatory sites. What are the molecular mechanisms of allosteric communication in proteins? We base our analysis on the hypothesis that a folded protein has a number of conformational degrees of freedom, which describe fluctuations around the native conformation and switching from/to functional states. Transitions between the protein states involved in function and its regulation are based on coherent conformational degrees of freedom. Motion of one part of a protein along such a degree of freedom, implies a correlated motion in other parts of the protein. By determining which binding sites are simultaneously affected by the same motion we find sites that are allosterically coupled, i.e. where binding at one site can cause a change in ligand-affinity at another. Leverage coupling, the quantity introduced to measure this type of connection, reflects allosteric communication between different binding sites. We show how it can be used to understand allostery in enzymes of different sizes as well as in large protein complexes such as chaperones. Analysis of leverage coupling provides guidance in targeting native and latent regulatory sites.
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Affiliation(s)
- Simon Mitternacht
- Computational Biology Unit/Uni Research, University of Bergen, Bergen, Norway
- Department of Informatics, University of Bergen, Bergen, Norway
| | - Igor N. Berezovsky
- Computational Biology Unit/Uni Research, University of Bergen, Bergen, Norway
- * E-mail:
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76
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Rusu M, Wriggers W. Evolutionary bidirectional expansion for the tracing of alpha helices in cryo-electron microscopy reconstructions. J Struct Biol 2011; 177:410-9. [PMID: 22155667 DOI: 10.1016/j.jsb.2011.11.029] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2011] [Revised: 11/22/2011] [Accepted: 11/28/2011] [Indexed: 01/10/2023]
Abstract
Cryo-electron microscopy (cryo-EM) enables the imaging of macromolecular complexes in near-native environments at resolutions that often permit the visualization of secondary structure elements. For example, alpha helices frequently show consistent patterns in volumetric maps, exhibiting rod-like structures of high density. Here, we introduce VolTrac (Volume Tracer) - a novel technique for the annotation of alpha-helical density in cryo-EM data sets. VolTrac combines a genetic algorithm and a bidirectional expansion with a tabu search strategy to trace helical regions. Our method takes advantage of the stochastic search by using a genetic algorithm to identify optimal placements for a short cylindrical template, avoiding exploration of already characterized tabu regions. These placements are then utilized as starting positions for the adaptive bidirectional expansion that characterizes the curvature and length of the helical region. The method reliably predicted helices with seven or more residues in experimental and simulated maps at intermediate (4-10Å) resolution. The observed success rates, ranging from 70.6% to 100%, depended on the map resolution and validation parameters. For successful predictions, the helical axes were located within 2Å from known helical axes of atomic structures.
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Affiliation(s)
- Mirabela Rusu
- School of Biomedical Informatics, The University of Texas Health Science Center at Houston, 7000 Fannin St., Houston, TX 77030, USA.
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77
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Mizobata T, Uemura T, Isaji K, Hirayama T, Hongo K, Kawata Y. Probing the functional mechanism of Escherichia coli GroEL using circular permutation. PLoS One 2011; 6:e26462. [PMID: 22028884 PMCID: PMC3196576 DOI: 10.1371/journal.pone.0026462] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Accepted: 09/27/2011] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The Escherichia coli chaperonin GroEL subunit consists of three domains linked via two hinge regions, and each domain is responsible for a specific role in the functional mechanism. Here, we have used circular permutation to study the structural and functional characteristics of the GroEL subunit. METHODOLOGY/PRINCIPAL FINDINGS Three soluble, partially active mutants with polypeptide ends relocated into various positions of the apical domain of GroEL were isolated and studied. The basic functional hallmarks of GroEL (ATPase and chaperoning activities) were retained in all three mutants. Certain functional characteristics, such as basal ATPase activity and ATPase inhibition by the cochaperonin GroES, differed in the mutants while at the same time, the ability to facilitate the refolding of rhodanese was roughly equal. Stopped-flow fluorescence experiments using a fluorescent variant of the circularly permuted GroEL CP376 revealed that a specific kinetic transition that reflects movements of the apical domain was missing in this mutant. This mutant also displayed several characteristics that suggested that the apical domains were behaving in an uncoordinated fashion. CONCLUSIONS/SIGNIFICANCE The loss of apical domain coordination and a concomitant decrease in functional ability highlights the importance of certain conformational signals that are relayed through domain interlinks in GroEL. We propose that circular permutation is a very versatile tool to probe chaperonin structure and function.
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Affiliation(s)
- Tomohiro Mizobata
- Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, Tottori, Japan.
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78
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Ahmed A, Whitford PC, Sanbonmatsu KY, Tama F. Consensus among flexible fitting approaches improves the interpretation of cryo-EM data. J Struct Biol 2011; 177:561-70. [PMID: 22019767 DOI: 10.1016/j.jsb.2011.10.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Revised: 10/05/2011] [Accepted: 10/06/2011] [Indexed: 12/31/2022]
Abstract
Cryo-elecron microscopy (cryo-EM) can provide important structural information of large macromolecular assemblies in different conformational states. Recent years have seen an increase in structures deposited in the Protein Data Bank (PDB) by fitting a high-resolution structure into its low-resolution cryo-EM map. A commonly used protocol for accommodating the conformational changes between the X-ray structure and the cryo-EM map is rigid body fitting of individual domains. With the emergence of different flexible fitting approaches, there is a need to compare and revise these different protocols for the fitting. We have applied three diverse automated flexible fitting approaches on a protein dataset for which rigid domain fitting (RDF) models have been deposited in the PDB. In general, a consensus is observed in the conformations, which indicates a convergence from these theoretically different approaches to the most probable solution corresponding to the cryo-EM map. However, the result shows that the convergence might not be observed for proteins with complex conformational changes or with missing densities in cryo-EM map. In contrast, RDF structures deposited in the PDB can represent conformations that not only differ from the consensus obtained by flexible fitting but also from X-ray crystallography. Thus, this study emphasizes that a "consensus" achieved by the use of several automated flexible fitting approaches can provide a higher level of confidence in the modeled configurations. Following this protocol not only increases the confidence level of fitting, but also highlights protein regions with uncertain fitting. Hence, this protocol can lead to better interpretation of cryo-EM data.
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Affiliation(s)
- Aqeel Ahmed
- Department of Chemistry and Biochemistry, The University of Arizona, 1041 E. Lowell Street, Tucson, AZ 85721, USA.
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79
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Yang Z, Lasker K, Schneidman-Duhovny D, Webb B, Huang CC, Pettersen EF, Goddard TD, Meng EC, Sali A, Ferrin TE. UCSF Chimera, MODELLER, and IMP: an integrated modeling system. J Struct Biol 2011; 179:269-78. [PMID: 21963794 DOI: 10.1016/j.jsb.2011.09.006] [Citation(s) in RCA: 428] [Impact Index Per Article: 32.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Revised: 09/16/2011] [Accepted: 09/18/2011] [Indexed: 02/02/2023]
Abstract
Structural modeling of macromolecular complexes greatly benefits from interactive visualization capabilities. Here we present the integration of several modeling tools into UCSF Chimera. These include comparative modeling by MODELLER, simultaneous fitting of multiple components into electron microscopy density maps by IMP MultiFit, computing of small-angle X-ray scattering profiles and fitting of the corresponding experimental profile by IMP FoXS, and assessment of amino acid sidechain conformations based on rotamer probabilities and local interactions by Chimera.
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Affiliation(s)
- Zheng Yang
- Resource for Biocomputing, Visualization, and Informatics, Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94158, USA
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80
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Zhang J, Ma B, DiMaio F, Douglas NR, Joachimiak LA, Baker D, Frydman J, Levitt M, Chiu W. Cryo-EM structure of a group II chaperonin in the prehydrolysis ATP-bound state leading to lid closure. Structure 2011; 19:633-9. [PMID: 21565698 DOI: 10.1016/j.str.2011.03.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2010] [Revised: 03/02/2011] [Accepted: 03/05/2011] [Indexed: 10/18/2022]
Abstract
Chaperonins are large ATP-driven molecular machines that mediate cellular protein folding. Group II chaperonins use their "built-in lid" to close their central folding chamber. Here we report the structure of an archaeal group II chaperonin in its prehydrolysis ATP-bound state at subnanometer resolution using single particle cryo-electron microscopy (cryo-EM). Structural comparison of Mm-cpn in ATP-free, ATP-bound, and ATP-hydrolysis states reveals that ATP binding alone causes the chaperonin to close slightly with a ∼45° counterclockwise rotation of the apical domain. The subsequent ATP hydrolysis drives each subunit to rock toward the folding chamber and to close the lid completely. These motions are attributable to the local interactions of specific active site residues with the nucleotide, the tight couplings between the apical and intermediate domains within the subunit, and the aligned interactions between two subunits across the rings. This mechanism of structural changes in response to ATP is entirely different from those found in group I chaperonins.
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Affiliation(s)
- Junjie Zhang
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, National Center for Macromolecular Imaging, Baylor College of Medicine, Houston, TX 77030, USA
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81
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Li Y, Zheng Z, Ramsey A, Chen L. Analysis of peptides and proteins in their binding to GroEL. J Pept Sci 2011; 16:693-700. [PMID: 20814869 DOI: 10.1002/psc.1288] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The GroEL-GroES is an essential molecular chaperon system that assists protein folding in cell. Binding of various substrate proteins to GroEL is one of the key aspects in GroEL-assisted protein folding. Small peptides may mimic segments of the substrate proteins in contact with GroEL and allow detailed structural analysis of the interactions. A model peptide SBP has been shown to bind to a region in GroEL that is important for binding of substrate proteins. Here, we investigated whether the observed GroEL-SBP interaction represented those of GroEL-substrate proteins, and whether SBP was able to mimic various aspects of substrate proteins in GroE-assisted protein folding cycle. We found that SBP competed with substrate proteins, including α-lactalbumin, rhodanese, and malate dehydrogenase, in binding to GroEL. SBP stimulated GroEL ATP hydrolysis rate in a manner similar to that of α-lactalbumin. SBP did not prevent GroES from binding to GroEL, and GroES association reduced the ATPase rates of GroEL/SBP and GroEL/α-lactalbumin to a comparable extent. Binding of both SBP and α-lactalbumin to apo GroEL was dominated by hydrophobic interaction. Interestingly, association of α-lactalbumin to GroEL/GroES was thermodynamically distinct from that to GroEL with reduced affinity and decreased contribution from hydrophobic interaction. However, SBP did not display such differential binding behaviors to apo GroEL and GroEL/GroES, likely due to the lack of a contiguous polypeptide chain that links all of the bound peptide fragments. Nevertheless, studies using peptides provide valuable information on the nature of GroEL-substrate protein interaction, which is central to understand the mechanism of GroEL-assisted protein folding.
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Affiliation(s)
- Yali Li
- Interdisciplinary Biochemistry Program, Indiana University, 212 S. Hawthorne Dr., Bloomington, IN 47405, USA
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82
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Fuchigami S, Fujisaki H, Matsunaga Y, Kidera A. Protein Functional Motions: Basic Concepts and Computational Methodologies. ADVANCING THEORY FOR KINETICS AND DYNAMICS OF COMPLEX, MANY-DIMENSIONAL SYSTEMS: CLUSTERS AND PROTEINS 2011. [DOI: 10.1002/9781118087817.ch2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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83
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Yébenes H, Mesa P, Muñoz IG, Montoya G, Valpuesta JM. Chaperonins: two rings for folding. Trends Biochem Sci 2011; 36:424-32. [PMID: 21723731 DOI: 10.1016/j.tibs.2011.05.003] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 05/13/2011] [Accepted: 05/18/2011] [Indexed: 01/08/2023]
Abstract
Chaperonins are ubiquitous chaperones found in Eubacteria, eukaryotic organelles (group I), Archaea and the eukaryotic cytosol (group II). They all share a common structure and a basic functional mechanism. Although a large amount of information has been gathered for the simpler group I, much less is known about group II chaperonins. Recent crystallographic and electron microscopy structures have provided new insights into the mechanism of these chaperonins and revealed important differences between group I and II chaperonins, mainly in the molecular rearrangements that take place during the functional cycle. These differences are evident for the most complex chaperonin, the eukaryotic cytosolic CCT, which highlights the uniqueness of this important molecular machine.
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Affiliation(s)
- Hugo Yébenes
- Centro Nacional de Biotecnología (CNB-CSIC), Campus de la Universidad Autónoma de Madrid, Darwin 3, 28049 Madrid, Spain
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84
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Núñez-Ramírez R, Klinge S, Sauguet L, Melero R, Recuero-Checa MA, Kilkenny M, Perera RL, García-Alvarez B, Hall RJ, Nogales E, Pellegrini L, Llorca O. Flexible tethering of primase and DNA Pol α in the eukaryotic primosome. Nucleic Acids Res 2011; 39:8187-99. [PMID: 21715379 PMCID: PMC3185431 DOI: 10.1093/nar/gkr534] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The Pol α/primase complex or primosome is the primase/polymerase complex that initiates nucleic acid synthesis during eukaryotic replication. Within the primosome, the primase synthesizes short RNA primers that undergo limited extension by Pol α. The resulting RNA–DNA primers are utilized by Pol δ and Pol ε for processive elongation on the lagging and leading strands, respectively. Despite its importance, the mechanism of RNA–DNA primer synthesis remains poorly understood. Here, we describe a structural model of the yeast primosome based on electron microscopy and functional studies. The 3D architecture of the primosome reveals an asymmetric, dumbbell-shaped particle. The catalytic centers of primase and Pol α reside in separate lobes of high relative mobility. The flexible tethering of the primosome lobes increases the efficiency of primer transfer between primase and Pol α. The physical organization of the primosome suggests that a concerted mechanism of primer hand-off between primase and Pol α would involve coordinated movements of the primosome lobes. The first three-dimensional map of the eukaryotic primosome at 25 Å resolution provides an essential structural template for understanding initiation of eukaryotic replication.
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Affiliation(s)
- Rafael Núñez-Ramírez
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Ramiro de Maetzu 9, 28040 Madrid, Spain, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK and University of California, 742 Stanley Hall, MS 3220, Berkeley, CA 94720-3220, USA
| | - Sebastian Klinge
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Ramiro de Maetzu 9, 28040 Madrid, Spain, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK and University of California, 742 Stanley Hall, MS 3220, Berkeley, CA 94720-3220, USA
| | - Ludovic Sauguet
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Ramiro de Maetzu 9, 28040 Madrid, Spain, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK and University of California, 742 Stanley Hall, MS 3220, Berkeley, CA 94720-3220, USA
| | - Roberto Melero
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Ramiro de Maetzu 9, 28040 Madrid, Spain, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK and University of California, 742 Stanley Hall, MS 3220, Berkeley, CA 94720-3220, USA
| | - María A. Recuero-Checa
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Ramiro de Maetzu 9, 28040 Madrid, Spain, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK and University of California, 742 Stanley Hall, MS 3220, Berkeley, CA 94720-3220, USA
| | - Mairi Kilkenny
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Ramiro de Maetzu 9, 28040 Madrid, Spain, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK and University of California, 742 Stanley Hall, MS 3220, Berkeley, CA 94720-3220, USA
| | - Rajika L. Perera
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Ramiro de Maetzu 9, 28040 Madrid, Spain, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK and University of California, 742 Stanley Hall, MS 3220, Berkeley, CA 94720-3220, USA
| | - Begoña García-Alvarez
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Ramiro de Maetzu 9, 28040 Madrid, Spain, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK and University of California, 742 Stanley Hall, MS 3220, Berkeley, CA 94720-3220, USA
| | - Richard J. Hall
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Ramiro de Maetzu 9, 28040 Madrid, Spain, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK and University of California, 742 Stanley Hall, MS 3220, Berkeley, CA 94720-3220, USA
| | - Eva Nogales
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Ramiro de Maetzu 9, 28040 Madrid, Spain, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK and University of California, 742 Stanley Hall, MS 3220, Berkeley, CA 94720-3220, USA
| | - Luca Pellegrini
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Ramiro de Maetzu 9, 28040 Madrid, Spain, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK and University of California, 742 Stanley Hall, MS 3220, Berkeley, CA 94720-3220, USA
- *To whom correspondence should be addressed. Tel: +34 918373112 (Ext. 4446); Fax: +34 915360432;
| | - Oscar Llorca
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Ramiro de Maetzu 9, 28040 Madrid, Spain, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK and University of California, 742 Stanley Hall, MS 3220, Berkeley, CA 94720-3220, USA
- *To whom correspondence should be addressed. Tel: +34 918373112 (Ext. 4446); Fax: +34 915360432;
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Skjaerven L, Grant B, Muga A, Teigen K, McCammon JA, Reuter N, Martinez A. Conformational sampling and nucleotide-dependent transitions of the GroEL subunit probed by unbiased molecular dynamics simulations. PLoS Comput Biol 2011; 7:e1002004. [PMID: 21423709 PMCID: PMC3053311 DOI: 10.1371/journal.pcbi.1002004] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Accepted: 12/09/2010] [Indexed: 12/01/2022] Open
Abstract
GroEL is an ATP dependent molecular chaperone that promotes the folding of a large number of substrate proteins in E. coli. Large-scale conformational transitions occurring during the reaction cycle have been characterized from extensive crystallographic studies. However, the link between the observed conformations and the mechanisms involved in the allosteric response to ATP and the nucleotide-driven reaction cycle are not completely established. Here we describe extensive (in total long) unbiased molecular dynamics (MD) simulations that probe the response of GroEL subunits to ATP binding. We observe nucleotide dependent conformational transitions, and show with multiple 100 ns long simulations that the ligand-induced shift in the conformational populations are intrinsically coded in the structure-dynamics relationship of the protein subunit. Thus, these simulations reveal a stabilization of the equatorial domain upon nucleotide binding and a concomitant “opening” of the subunit, which reaches a conformation close to that observed in the crystal structure of the subunits within the ADP-bound oligomer. Moreover, we identify changes in a set of unique intrasubunit interactions potentially important for the conformational transition. Molecular machines convert chemical energy to mechanical work in the process of carrying out their specific tasks. Often these proteins are fueled by ATP binding and hydrolysis, enabling switching between different conformations. The ATP-dependent chaperone GroEL is a molecular machine that opens and closes its barrel-like structure in order to provide a folding cage for unfolded proteins. The quest to fully understand and control GroEL and other molecular machines is enhanced by complementing experimental work with computational approaches. Here, we provide a description of the molecular basis for the conformational changes in the GroEL subunit by performing extensive molecular dynamics simulations. The simulations sample the conformational population for the different nucleotide-free and bound states in the isolated subunit. The results reveal that the conformations of the subunit when isolated resemble those of the subunit integrated in the GroEL complex. Moreover, the molecular dynamics simulations allow following detailed changes in individual interatomic interactions brought about by ATP-binding.
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Affiliation(s)
- Lars Skjaerven
- Department of Biomedicine, University of Bergen, Bergen, Norway
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87
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Lasker K, Sali A, Wolfson HJ. Determining macromolecular assembly structures by molecular docking and fitting into an electron density map. Proteins 2011; 78:3205-11. [PMID: 20827723 DOI: 10.1002/prot.22845] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Structural models of macromolecular assemblies are instrumental for gaining a mechanistic understanding of cellular processes. Determining these structures is a major challenge for experimental techniques, such as X-ray crystallography, NMR spectroscopy and electron microscopy (EM). Thus, computational modeling techniques, including molecular docking, are required. The development of most molecular docking methods has so far been focused on modeling of binary complexes. We have recently introduced the MultiFit method for modeling the structure of a multisubunit complex by simultaneously optimizing the fit of the model into an EM density map of the entire complex and the shape complementarity between interacting subunits. Here, we report algorithmic advances of the MultiFit method that result in an efficient and accurate assembly of the input subunits into their density map. The successful predictions and the increasing number of complexes being characterized by EM suggests that the CAPRI challenge could be extended to include docking-based modeling of macromolecular assemblies guided by EM.
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Affiliation(s)
- Keren Lasker
- Raymond and Beverly Sackler Faculty of Exact Sciences, Blavatnik School of Computer Science, Tel Aviv University, Tel Aviv 69978, Israel
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88
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Birmanns S, Rusu M, Wriggers W. Using Sculptor and Situs for simultaneous assembly of atomic components into low-resolution shapes. J Struct Biol 2010; 173:428-35. [PMID: 21078392 DOI: 10.1016/j.jsb.2010.11.002] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Revised: 10/31/2010] [Accepted: 11/04/2010] [Indexed: 10/18/2022]
Abstract
We describe an integrated software system called Sculptor that combines visualization capabilities with molecular modeling algorithms for the analysis of multi-scale data sets. Sculptor features extensive special purpose visualization techniques that are based on modern GPU programming and are capable of representing complex molecular assemblies in real-time. The integration of graphics and modeling offers several advantages. The user interface not only eases the usually steep learning curve of pure algorithmic techniques, but it also permits instant analysis and post-processing of results, as well as the integration of results from external software. Here, we implemented an interactive peak-selection strategy that enables the user to explore a preliminary score landscape generated by the colors tool of Situs. The interactive placement of components, one at a time, is advantageous for low-resolution or ambiguously shaped maps, which are sometimes difficult to interpret by the fully automatic peak selection of colors. For the subsequent refinement of the preliminary models resulting from both interactive and automatic peak selection, we have implemented a novel simultaneous multi-body docking in Sculptor and Situs that softly enforces shape complementarities between components using the normalization of the cross-correlation coefficient. The proposed techniques are freely available in Situs version 2.6 and Sculptor version 2.0.
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Affiliation(s)
- Stefan Birmanns
- University of Texas School of Biomedical Informatics at Houston, 7000 Fannin St. UCT 600, Houston, TX 77030, USA.
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89
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Tekpinar M, Zheng W. Predicting order of conformational changes during protein conformational transitions using an interpolated elastic network model. Proteins 2010; 78:2469-81. [PMID: 20602461 DOI: 10.1002/prot.22755] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The decryption of sequence of structural events during protein conformational transitions is essential to a detailed understanding of molecular functions of various biological nanomachines. Coarse-grained models have proven useful by allowing highly efficient simulations of protein conformational dynamics. By combining two coarse-grained elastic network models constructed based on the beginning and end conformations of a transition, we have developed an interpolated elastic network model to generate a transition pathway between the two protein conformations. For validation, we have predicted the order of local and global conformational changes during key ATP-driven transitions in three important biological nanomachines (myosin, F(1) ATPase and chaperonin GroEL). We have found that the local conformational change associated with the closing of active site precedes the global conformational change leading to mechanical motions. Our finding is in good agreement with the distribution of intermediate experimental structures, and it supports the importance of local motions at active site to drive or gate various conformational transitions underlying the workings of a diverse range of biological nanomachines.
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Affiliation(s)
- Mustafa Tekpinar
- Department of Physics, University at Buffalo, Buffalo, New York 14260, USA
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90
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Lawson CL, Baker ML, Best C, Bi C, Dougherty M, Feng P, van Ginkel G, Devkota B, Lagerstedt I, Ludtke SJ, Newman RH, Oldfield TJ, Rees I, Sahni G, Sala R, Velankar S, Warren J, Westbrook JD, Henrick K, Kleywegt GJ, Berman HM, Chiu W. EMDataBank.org: unified data resource for CryoEM. Nucleic Acids Res 2010; 39:D456-64. [PMID: 20935055 PMCID: PMC3013769 DOI: 10.1093/nar/gkq880] [Citation(s) in RCA: 192] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Cryo-electron microscopy reconstruction methods are uniquely able to reveal structures of many important macromolecules and macromolecular complexes. EMDataBank.org, a joint effort of the Protein Data Bank in Europe (PDBe), the Research Collaboratory for Structural Bioinformatics (RCSB) and the National Center for Macromolecular Imaging (NCMI), is a global ‘one-stop shop’ resource for deposition and retrieval of cryoEM maps, models and associated metadata. The resource unifies public access to the two major archives containing EM-based structural data: EM Data Bank (EMDB) and Protein Data Bank (PDB), and facilitates use of EM structural data of macromolecules and macromolecular complexes by the wider scientific community.
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Affiliation(s)
- Catherine L Lawson
- Department of Chemistry and Chemical Biology and Research Collaboratory for Structural Bioinformatics, Rutgers, The State University of New Jersey, 610 Taylor Road Piscataway, NJ 08854, USA.
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91
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Gymnastics of Molecular Chaperones. Mol Cell 2010; 39:321-31. [DOI: 10.1016/j.molcel.2010.07.012] [Citation(s) in RCA: 253] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2010] [Revised: 06/14/2010] [Accepted: 07/09/2010] [Indexed: 11/20/2022]
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92
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Zhang S, Vasishtan D, Xu M, Topf M, Alber F. A fast mathematical programming procedure for simultaneous fitting of assembly components into cryoEM density maps. Bioinformatics 2010; 26:i261-8. [PMID: 20529915 PMCID: PMC2881386 DOI: 10.1093/bioinformatics/btq201] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
MOTIVATION Single-particle cryo electron microscopy (cryoEM) typically produces density maps of macromolecular assemblies at intermediate to low resolution (approximately 5-30 A). By fitting high-resolution structures of assembly components into these maps, pseudo-atomic models can be obtained. Optimizing the quality-of-fit of all components simultaneously is challenging due to the large search space that makes the exhaustive search over all possible component configurations computationally unfeasible. RESULTS We developed an efficient mathematical programming algorithm that simultaneously fits all component structures into an assembly density map. The fitting is formulated as a point set matching problem involving several point sets that represent component and assembly densities at a reduced complexity level. In contrast to other point matching algorithms, our algorithm is able to match multiple point sets simultaneously and not only based on their geometrical equivalence, but also based on the similarity of the density in the immediate point neighborhood. In addition, we present an efficient refinement method based on the Iterative Closest Point registration algorithm. The integer quadratic programming method generates an assembly configuration in a few seconds. This efficiency allows the generation of an ensemble of candidate solutions that can be assessed by an independent scoring function. We benchmarked the method using simulated density maps of 11 protein assemblies at 20 A, and an experimental cryoEM map at 23.5 A resolution. Our method was able to generate assembly structures with root-mean-square errors <6.5 A, which have been further reduced to <1.8 A by the local refinement procedure. AVAILABILITY The program is available upon request as a Matlab code package. SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics Online.
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Affiliation(s)
- Shihua Zhang
- Program in Molecular and Computational Biology, University of Southern California, Los Angeles, CA, USA
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93
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Kim KT, Meeuwissen SA, Nolte RJM, van Hest JCM. Smart nanocontainers and nanoreactors. NANOSCALE 2010; 2:844-858. [PMID: 20648280 DOI: 10.1039/b9nr00409b] [Citation(s) in RCA: 132] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We highlight recent advances in the synthesis of nanocarriers and nanoreactors from synthetic and biological building blocks with emphasis on the stimulus-responsive regulation of their function.
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Affiliation(s)
- Kyoung Taek Kim
- Radboud University Nijmegen, Institute for Molecules and Materials, Heyendaalseweg 135, Nijmegen, 6525, AJ, The Netherlands
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94
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Out-of-equilibrium conformational cycling of GroEL under saturating ATP concentrations. Proc Natl Acad Sci U S A 2010; 107:6270-4. [PMID: 20308583 DOI: 10.1073/pnas.0910246107] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The molecular chaperone GroEL exists in at least two allosteric states, T and R, that interconvert in an ATP-controlled manner. Thermodynamic analysis suggests that the T-state population becomes negligible with increasing ATP concentrations, in conflict with the requirement for conformational cycling, which is essential for the operation of molecular machines. To solve this conundrum, we performed fluorescence correlation spectroscopy on the single-ring version of GroEL, using a fluorescent switch recently built into its structure, which turns "on," i.e., increases its fluorescence dramatically, when ATP is added. A series of correlation functions was measured as a function of ATP concentration and analyzed using singular-value decomposition. The analysis assigned the signal to two states whose dynamics clearly differ. Surprisingly, even at ATP saturation, approximately 50% of the molecules still populate the T state at any instance of time, indicating constant out-of-equilibrium cycling between T and R. Only upon addition of the cochaperonin GroES does the T-state population vanish. Our results suggest a model in which the T/R ratio is controlled by the rate of ADP release after hydrolysis, which can be determined accordingly.
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95
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Oligomeric structure of brain abundant proteins GAP-43 and BASP1. J Struct Biol 2010; 170:470-83. [PMID: 20109554 DOI: 10.1016/j.jsb.2010.01.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Revised: 12/21/2009] [Accepted: 01/20/2010] [Indexed: 11/19/2022]
Abstract
Brain abundant proteins GAP-43 and BASP1 participate in the regulation of actin cytoskeleton dynamics in neuronal axon terminals. The proposed mechanism suggests that the proteins sequester phosphatidylinositol-4,5-diphosphate (PIP(2)) in the inner leaflet of the plasma membrane. We found that model anionic phospholipid membranes in the form of liposomes induce rapid oligomerization of GAP-43 and BASP1 proteins. Multiply charged phosphoinositides produced the most potent effect. Anionic detergent sodium dodecyl sulfate (SDS) at submicellar concentration stimulated formation of similar oligomers in solution. BASP1, but not GAP-43, also formed oligomers at sufficiently high concentration in the absence of lipids and SDS. Electron microscopy study demonstrated that the oligomers have disk-shaped or annular structure of 10-30nm in diameter. BASP1 also formed higher aggregates of linear rod-like structure, with average length of about 100nm. In outward appearance, the oligomers and linear aggregates are reminiscent of oligomers and protofibrils of amyloid proteins. Both the synthetic N-terminal peptide GAP-43(1-40) and the brain-derived fragment GAP-43-3 preserved the ability to oligomerize under the action of acidic phospholipids and SDS. On the contrary, BASP1 fragment truncated by the short N-terminal myristoylated peptide was unable to form oligomers. GAP-43 and BASP1 oligomerization can be regulated by calmodulin, which disrupts the oligomers and displaces the proteins from the membrane. We suggest that in vivo, the role of membrane-bound GAP-43 and BASP1 oligomers consists in accumulation of PIP(2) in functional clusters, which become accessible for other PIP(2)-binding proteins after dissociation of the oligomers.
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96
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ATP-triggered ADP release from the asymmetric chaperonin GroEL/GroES/ADP7 is not the rate-limiting step of the GroEL/GroES reaction cycle. FEBS Lett 2010; 584:951-3. [PMID: 20083109 PMCID: PMC2849271 DOI: 10.1016/j.febslet.2010.01.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2009] [Revised: 01/11/2010] [Accepted: 01/12/2010] [Indexed: 11/23/2022]
Abstract
The GroEL/GroES protein folding chamber is formed and dissociated by ATP binding and hydrolysis. ATP hydrolysis in the GroES-bound (cis) ring gates entry of ATP into the opposite unoccupied trans ring, which allosterically ejects cis ligands. While earlier studies suggested that hydrolysis of cis ATP is the rate-limiting step of the cycle (t1/2 approximately 10 s), a recent study suggested that ADP release from the cis ring may be rate-limiting (t1/2 approximately 15-20 s). Here we have measured ADP release using a coupled enzyme assay and observed a t1/2 for release of <or=4-5 s, indicating that this is not the rate-limiting step of the reaction cycle.
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97
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Noi K, Hirai H, Hongo K, Mizobata T, Kawata Y. A potentially versatile nucleotide hydrolysis activity of group II chaperonin monomers from Thermoplasma acidophilum. Biochemistry 2009; 48:9405-15. [PMID: 19728744 DOI: 10.1021/bi900959c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Compared to the group I chaperonins such as Escherichia coli GroEL, which facilitate protein folding, many aspects of the functional mechanism of archaeal group II chaperonins are still unclear. Here, we show that monomeric forms of archaeal group II chaperonin alpha and beta from Thermoplasma acidophilum may be purified stably and that these monomers display a strong AMPase activity in the presence of divalent ions, especially Co(2+) ion, in addition to ATPase and ADPase activities. Furthermore, other nucleoside phosphates (guanosine, cytidine, uridine, and inosine phosphates) in addition to adenine nucleotides were hydrolyzed. From analyses of the products of hydrolysis using HPLC, it was revealed that the monomeric chaperonin successively hydrolyzed the phosphoanhydride and phosphoester bonds of ATP in the order of gamma to alpha. This activity was strongly suppressed by point mutation of specific essential aspartic acid residues. Although these archaeal monomeric chaperonins did not alter the refolding of MDH, their novel versatile nucleotide hydrolysis activity might fulfill a new function. Western blot experiments demonstrated that the monomeric chaperonin subunits were also present in lysed cell extracts of T. acidophilum, and partially purified native monomer displayed Co(2+)-dependent AMPase activity.
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Affiliation(s)
- Kentaro Noi
- Department of Chemistry and Biotechnology, Graduate School of Engineering, Institute of Regenerative Medicine Biofunction, Graduate School of Medical Science, Tottori University, Tottori 680-8552, Japan
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98
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Aryal RP, Ju T, Cummings RD. The endoplasmic reticulum chaperone Cosmc directly promotes in vitro folding of T-synthase. J Biol Chem 2009; 285:2456-62. [PMID: 19923218 DOI: 10.1074/jbc.m109.065169] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The T-synthase is the key beta 3-galactosyltransferase essential for biosynthesis of core 1 O-glycans (Gal beta 1-3GalNAc alpha 1-Ser/Thr) in animal cell glycoproteins. Here we describe the novel ability of an endoplasmic reticulum-localized molecular chaperone termed Cosmc to specifically interact with partly denatured T-synthase in vitro to cause partial restoration of activity. By contrast, a mutated form of Cosmc observed in patients with Tn syndrome has reduced chaperone function. The chaperone activity of Cosmc is specific, does not require ATP in vitro, and is effective toward T-synthase but not another beta-galactosyltransferase. Cosmc represents the first ER chaperone identified to be required for folding of a glycosyltransferase.
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Affiliation(s)
- Rajindra P Aryal
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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99
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GroEL/GroES cycling: ATP binds to an open ring before substrate protein favoring protein binding and production of the native state. Proc Natl Acad Sci U S A 2009; 106:20264-9. [PMID: 19915138 DOI: 10.1073/pnas.0911556106] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The GroEL/GroES reaction cycle involves steps of ATP and polypeptide binding to an open GroEL ring before the GroES encapsulation step that triggers productive folding in a sequestered chamber. The physiological order of addition of ATP and nonnative polypeptide, typically to the open trans ring of an asymmetrical GroEL/GroES/ADP complex, has been unknown, although there have been assumptions that polypeptide binds first, allowing subsequent ATP-mediated movement of the GroEL apical domains to exert an action of forceful unfolding on the nonnative polypeptide. Here, using fluorescence measurements, we show that the physiological order of addition is the opposite, involving rapid binding of ATP, accompanied by nearly as rapid apical domain movements, followed by slower binding of nonnative polypeptide. In order-of-addition experiments, approximately twice as much Rubisco activity was recovered when nonnative substrate protein was added after ATP compared with it being added before ATP, associated with twice as much Rubisco protein recovered with the chaperonin. Furthermore, the rate of Rubisco binding to an ATP-exposed ring was twice that observed in the absence of nucleotide. Finally, when both ATP and Rubisco were added simultaneously to a GroEL ring, simulating the physiological situation, the rate of Rubisco binding corresponded to that observed when ATP had been added first. We conclude that the physiological order, ATP binding before polypeptide, enables more efficient capture of nonnative substrate proteins, and thus allows greater recovery of the native state for any given round of the chaperonin cycle.
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100
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Lu HM, Liang J. Perturbation-based Markovian transmission model for probing allosteric dynamics of large macromolecular assembling: a study of GroEL-GroES. PLoS Comput Biol 2009; 5:e1000526. [PMID: 19798437 PMCID: PMC2741606 DOI: 10.1371/journal.pcbi.1000526] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2009] [Accepted: 08/31/2009] [Indexed: 11/19/2022] Open
Abstract
Large macromolecular assemblies are often important for biological processes in cells. Allosteric communications between different parts of these molecular machines play critical roles in cellular signaling. Although studies of the topology and fluctuation dynamics of coarse-grained residue networks can yield important insights, they do not provide characterization of the time-dependent dynamic behavior of these macromolecular assemblies. Here we develop a novel approach called Perturbation-based Markovian Transmission (PMT) model to study globally the dynamic responses of the macromolecular assemblies. By monitoring simultaneous responses of all residues (>8,000) across many (>6) decades of time spanning from the initial perturbation until reaching equilibrium using a Krylov subspace projection method, we show that this approach can yield rich information. With criteria based on quantitative measurements of relaxation half-time, flow amplitude change, and oscillation dynamics, this approach can identify pivot residues that are important for macromolecular movement, messenger residues that are key to signal mediating, and anchor residues important for binding interactions. Based on a detailed analysis of the GroEL-GroES chaperone system, we found that our predictions have an accuracy of 71-84% judged by independent experimental studies reported in the literature. This approach is general and can be applied to other large macromolecular machineries such as the virus capsid and ribosomal complex.
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Affiliation(s)
- Hsiao-Mei Lu
- Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Jie Liang
- Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States of America
- * E-mail:
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