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Kaur U, Meng H, Lui F, Ma R, Ogburn RN, Johnson JHR, Fitzgerald MC, Jones LM. Proteome-Wide Structural Biology: An Emerging Field for the Structural Analysis of Proteins on the Proteomic Scale. J Proteome Res 2018; 17:3614-3627. [PMID: 30222357 DOI: 10.1021/acs.jproteome.8b00341] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Over the past decade, a suite of new mass-spectrometry-based proteomics methods has been developed that now enables the conformational properties of proteins and protein-ligand complexes to be studied in complex biological mixtures, from cell lysates to intact cells. Highlighted here are seven of the techniques in this new toolbox. These techniques include chemical cross-linking (XL-MS), hydroxyl radical footprinting (HRF), Drug Affinity Responsive Target Stability (DARTS), Limited Proteolysis (LiP), Pulse Proteolysis (PP), Stability of Proteins from Rates of Oxidation (SPROX), and Thermal Proteome Profiling (TPP). The above techniques all rely on conventional bottom-up proteomics strategies for peptide sequencing and protein identification. However, they have required the development of unconventional proteomic data analysis strategies. Discussed here are the current technical challenges associated with these different data analysis strategies as well as the relative analytical capabilities of the different techniques. The new biophysical capabilities that the above techniques bring to bear on proteomic research are also highlighted in the context of several different application areas in which these techniques have been used, including the study of protein ligand binding interactions (e.g., protein target discovery studies and protein interaction network analyses) and the characterization of biological states.
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Affiliation(s)
- Upneet Kaur
- Department of Pharmaceutical Sciences , University of Maryland , Baltimore , Maryland 21201 , United States
| | - He Meng
- Department of Chemistry , Duke University , Durham , North Carolina 27708-0346 , United States
| | | | - Renze Ma
- Department of Chemistry , Duke University , Durham , North Carolina 27708-0346 , United States
| | - Ryenne N Ogburn
- Department of Chemistry , Duke University , Durham , North Carolina 27708-0346 , United States
| | - Julia H R Johnson
- Department of Chemistry , Duke University , Durham , North Carolina 27708-0346 , United States
| | - Michael C Fitzgerald
- Department of Chemistry , Duke University , Durham , North Carolina 27708-0346 , United States
| | - Lisa M Jones
- Department of Pharmaceutical Sciences , University of Maryland , Baltimore , Maryland 21201 , United States
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52
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Ferreira LA, Walczyk Mooradally A, Zaslavsky B, Uversky VN, Graether SP. Effect of an Intrinsically Disordered Plant Stress Protein on the Properties of Water. Biophys J 2018; 115:1696-1706. [PMID: 30297135 DOI: 10.1016/j.bpj.2018.09.014] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 09/09/2018] [Accepted: 09/18/2018] [Indexed: 11/19/2022] Open
Abstract
Dehydrins are plant proteins that are able to protect plants from various forms of dehydrative stress such as drought, cold, and high salinity. Dehydrins can prevent enzymes from losing activity after freeze/thaw treatments. Previous studies had suggested that the dehydrins function by a molecular shield effect, essentially preventing a denatured enzyme from aggregating with another enzyme. Therefore, the larger the dehydrin, the larger the shield and theoretically the more effective the protection. Although this relationship holds for smaller dehydrins, it fails to explain why larger dehydrins are less efficient than would be predicted from their size. Using solvatochromic dyes to probe the solvent features of water, we first confirm that the dehydrins do not bind the dyes, which would interfere with interpretation of the data. We then show that the dehydrins have an effect on three solvent properties of water (dipolarity/polarizability, hydrogen-bond donor acidity and hydrogen-bond acceptor basicity), which can contribute to the protective mechanism of these proteins. Interpretation of these data suggests that although polyethylene glycol and dehydrins have similar protective effects, dehydrins may more efficiently modify the hydrogen-bonding ability of bulk water to prevent enzyme denaturation. This possibly explains why dehydrins recover slightly more enzyme activity than polyethylene glycol.
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Affiliation(s)
| | | | | | - Vladimir N Uversky
- Department of Molecular Medicine and Byrd Alzheimer's Research Institute, Morsani College of Medicine, University of South Florida, Tampa, Florida; Institute for Biological Instrumentation, Russian Academy of Sciences, Pushchino, Moscow Region, Russian Federation.
| | - Steffen P Graether
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada.
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53
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Kumar R, Sharma D, Kumar V, Kumar R. Factors defining the effects of macromolecular crowding on dynamics and thermodynamic stability of heme proteins in-vitro. Arch Biochem Biophys 2018; 654:146-162. [DOI: 10.1016/j.abb.2018.07.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 07/18/2018] [Accepted: 07/20/2018] [Indexed: 11/28/2022]
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54
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Ishrat M, Hassan MI, Ahmad F, Islam A. Sugar osmolytes-induced stabilization of RNase A in macromolecular crowded cellular environment. Int J Biol Macromol 2018; 115:349-357. [PMID: 29665392 DOI: 10.1016/j.ijbiomac.2018.04.073] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 03/27/2018] [Accepted: 04/13/2018] [Indexed: 10/17/2022]
Abstract
Organisms synthesize sugar osmolytes during environmental stresses to protect proteins against denaturation. These studies were carried out in dilute buffer whereas intracellular milieu within cells has cytoplasmic concentration of macromolecules in the range of 80-400 mg ml-1. Is the stabilizing effect of sugar osmolytes on the protein in dilute buffer different from that when protein is in cellular environment? To answer this question, we have measured and analysed the effect of sugar osmolytes on the structural and thermodynamic stability of ribonuclease A in the presence of dextran 70 at multiple concentrations of six sugars at different pH values. It was found that (i) each sugar osmolyte in the crowded environment provides stability to the protein in terms of Tm (midpoint of denaturation) and ∆GD° (Gibbs energy change) and this stabilizing effect is under entropic control, (ii) the extent of osmolyte-induced stabilization of RNase A is pH dependent, and (iii) effect of sugars on the stability of protein in presence of the crowding agent remains unchanged. This study concludes that crowding does not affect the efficacy of osmolytes and vice versa; and emphasizes on understanding of internal architecture of the cellular environment with respect to molecular and macromolecular crowding.
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Affiliation(s)
- Moin Ishrat
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India
| | - Md Imtaiyaz Hassan
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India
| | - Faizan Ahmad
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India
| | - Asimul Islam
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India.
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55
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Crowded milieu tuning the stability and activity of stem bromelain. Int J Biol Macromol 2018; 109:114-123. [DOI: 10.1016/j.ijbiomac.2017.12.060] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 12/06/2017] [Accepted: 12/08/2017] [Indexed: 11/24/2022]
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56
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Rivas G, Minton AP. Toward an understanding of biochemical equilibria within living cells. Biophys Rev 2018; 10:241-253. [PMID: 29235084 PMCID: PMC5899707 DOI: 10.1007/s12551-017-0347-6] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 11/13/2017] [Indexed: 12/19/2022] Open
Abstract
Four types of environmental effects that can affect macromolecular reactions in a living cell are defined: nonspecific intermolecular interactions, side reactions, partitioning between microenvironments, and surface interactions. Methods for investigating these interactions and their influence on target reactions in vitro are reviewed. Methods employed to characterize conformational and association equilibria in vivo are reviewed and difficulties in their interpretation cataloged. It is concluded that, in order to be amenable to unambiguous interpretation, in vivo studies must be complemented by in vitro studies carried out in well-characterized and controllable media designed to contain key elements of selected intracellular microenvironments.
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Affiliation(s)
- Germán Rivas
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Allen P. Minton
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892 USA
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57
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Marianelli AM, Miller BM, Keating CD. Impact of macromolecular crowding on RNA/spermine complex coacervation and oligonucleotide compartmentalization. SOFT MATTER 2018; 14:368-378. [PMID: 29265152 DOI: 10.1039/c7sm02146a] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report the effect of neutral macromolecular crowders poly(ethylene glycol) (PEG) (8 kDa) and Ficoll (70 kDa) on liquid-liquid phase separation in a polyuridylic acid (polyU)/spermine complex coacervate system. The addition of PEG decreased both the amount of spermine required for phase separation and the coacervation temperature (TC). We interpret these effects on phase behavior as arising due to excluded volume and preferential interactions on both the secondary structure/condensation of spermine-associated polyU molecules and on the association of soluble polyU/spermine polyelectrolyte complexes to form coacervate droplets. Examination of coacervates formed in the presence of fluorescently-labeled PEG or Ficoll crowders indicated that Ficoll is accumulated while PEG is excluded from the coacervate phase, which provides further insight into the differences in phase behavior. Crowding agents impact distribution of a biomolecular solute: partitioning of a fluorescently-labeled U15 RNA oligomer into the polyU/spermine coacervates was increased approximately two-fold by 20 wt% Ficoll 70 kDa and by more than two orders of magnitude by 20 wt% PEG 8 kDa. The volume of the coacervate phase decreased in the presence of crowder relative to a dilute buffer solution. These findings indicate that potential impacts of macromolecular crowding on phase behavior and solute partitioning should be considered in model systems for intracellular membraneless organelles.
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Affiliation(s)
- A M Marianelli
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
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58
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Acosta LC, Perez Goncalves GM, Pielak GJ, Gorensek-Benitez AH. Large cosolutes, small cosolutes, and dihydrofolate reductase activity. Protein Sci 2017; 26:2417-2425. [PMID: 28971539 DOI: 10.1002/pro.3316] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 09/27/2017] [Accepted: 09/27/2017] [Indexed: 11/06/2022]
Abstract
Protein enzymes are the main catalysts in the crowded and complex cellular interior, but their activity is almost always studied in dilute buffered solutions. Studies that attempt to recreate the cellular interior in vitro often utilize synthetic polymers as crowding agents. Here, we report the effects of the synthetic polymer cosolutes Ficoll, dextran, and polyvinylpyrrolidone, and their respective monomers, sucrose, glucose, and 1-ethyl-2-pyrrolidone, on the activity of the 18-kDa monomeric enzyme, Escherichia coli dihydrofolate reductase. At low concentrations, reductase activity increases relative to buffer and monomers, suggesting a macromolecular effect. However, the effect decreases at higher concentrations, approaching, and, in some cases, falling below buffer values. We also assessed activity in terms of volume occupancy, viscosity, and the overlap concentration (where polymers form an interwoven mesh). The trends vary with polymer family, but changes in activity are within threefold of buffer values. We also compiled and analyzed results from previous studies and conclude that alterations of steady-state enzyme kinetics in solutions crowded with synthetic polymers are idiosyncratic with respect to the crowding agent and enzyme.
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Affiliation(s)
| | | | - Gary J Pielak
- Department of Chemistry.,Department of Biochemistry and Biophysics.,Lineberger Comprehensive Cancer Center.,Integrative Program for Biological and Genome Sciences University of North Carolina, Chapel Hill, NC, 27599, USA
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Molecular origin of the weak susceptibility of kinesin velocity to loads and its relation to the collective behavior of kinesins. Proc Natl Acad Sci U S A 2017; 114:E8611-E8617. [PMID: 28973894 DOI: 10.1073/pnas.1710328114] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Motor proteins are active enzymatic molecules that support important cellular processes by transforming chemical energy into mechanical work. Although the structures and chemomechanical cycles of motor proteins have been extensively investigated, the sensitivity of a motor's velocity in response to a force is not well-understood. For kinesin, velocity is weakly influenced by a small to midrange external force (weak susceptibility) but is steeply reduced by a large force. Here, we utilize a structure-based molecular dynamic simulation to study the molecular origin of the weak susceptibility for a single kinesin. We show that the key step in controlling the velocity of a single kinesin under an external force is the ATP release from the microtubule-bound head. Only under large loading forces can the motor head release ATP at a fast rate, which significantly reduces the velocity of kinesin. It underpins the weak susceptibility that the velocity will not change at small to midrange forces. The molecular origin of this velocity reduction is that the neck linker of a kinesin only detaches from the motor head when pulled by a large force. This prompts the ATP binding site to adopt an open state, favoring ATP release and reducing the velocity. Furthermore, we show that two load-bearing kinesins are incapable of equally sharing the load unless they are very close to each other. As a consequence of the weak susceptibility, the trailing kinesin faces the challenge of catching up to the leading one, which accounts for experimentally observed weak cooperativity of kinesins motors.
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60
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Kumar S, Sharma D, Kumar R. Role of Macromolecular Crowding on Stability and Iron Release Kinetics of Serum Transferrin. J Phys Chem B 2017; 121:8669-8683. [PMID: 28837344 DOI: 10.1021/acs.jpcb.7b05702] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The macromolecular crowding influences the structural stability and functional properties of transferrin (Tf). The equilibrium as well as kinetic studies of Tf at different concentrations of crowding agents (dextran 40, dextran 70, and ficoll 70) and at a fixed concentration of dextran 40 under different concentrations of NaCl at pH 7.4 and 5.6 (±1) revealed that (i) the crowder environment increases the diferric-Tf (Fe2Tf) stability against iron loss and overall denaturation of the protein, (ii) both in the absence and presence of crowder, the presence of salt promotes the loss of iron and overall denaturation of Fe2Tf which is due to ionic screening of electrostatic interactions, (iii) the crowder environment retards iron release from monoferric N-lobe of Tf (FeNTf) by increasing enthalpic barrier, (iv) the retardation of iron release by crowding is enthalpically dominated than the entropic one, (v) both in the absence and presence of crowder, the presence of salt accelerates the iron release from FeNTf due to ionic screening of electrostatic interactions and anion binding to KISAB sites, and (vi) the crowders environment is unable to diminish (a) the salt-induced destabilization of Fe2Tf against the loss of iron and overall denaturation and (b) the anion effect and ionic screening of diffusive counterions responsible to promote iron release from FeNTf.
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Affiliation(s)
- Sandeep Kumar
- School of Chemistry and Biochemistry, Thapar University , Patiala 147004, India
| | - Deepak Sharma
- Council of Scientific and Industrial Research, Institute of Microbial Technology , Sector 39A, Chandigarh, India
| | - Rajesh Kumar
- Centre for Chemical Sciences, School of Bassic and Applied Sciences, Central University of Punjab , Bathinda 151001, India
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61
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Nasreen K, Ahamad S, Ahmad F, Hassan MI, Islam A. Macromolecular crowding induces molten globule state in the native myoglobin at physiological pH. Int J Biol Macromol 2017; 106:130-139. [PMID: 28811208 DOI: 10.1016/j.ijbiomac.2017.08.014] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Revised: 07/26/2017] [Accepted: 08/01/2017] [Indexed: 01/07/2023]
Abstract
Here, we report the formation of molten globule state of the native myoglobin in crowded environment. We have used Soret absorption spectroscopy and far-UV circular dichroism to monitor changes in tertiary and secondary structures of myoglobin, respectively. Our results reveal that in the presence of ficoll 70, the secondary structure of myoglobin remains unchanged while tertiary structure is lost significantly. 1-anilinonaphthalene-8-sulfonate binding experiments showed that myoglobin in the presence of various concentrations of ficoll 70, has newly exposed hydrophobic surfaces. Dynamic light scattering measurements show that there is almost 1.5 times increase in the hydrodynamic volume of myoglobin in the crowded environment. These structural characteristics of myoglobin in the presence of 300mg/ml ficoll 70 resemble those of molten globule state. Isothermal titration calorimetric (ITC) measurements show that ficoll 70 binds to myoglobin, whereas it shows no interaction with apo form of the protein. ITC results indicate that the reason behind this unique behavior of ficoll 70 towards myoglobin may be interaction of ficoll 70 with the heme group of myoglobin, which was further confirmed by the docking studies. We hypothesize that the soft interactions between heme and ficoll 70 leads to the formation of molten globule in myoglobin.
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Affiliation(s)
- Khalida Nasreen
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, 110025, India
| | - Shahzaib Ahamad
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, 110025, India
| | - Faizan Ahmad
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, 110025, India
| | - Md Imtaiyaz Hassan
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, 110025, India
| | - Asimul Islam
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, 110025, India.
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62
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Liu B, Åberg C, van Eerden FJ, Marrink SJ, Poolman B, Boersma AJ. Design and Properties of Genetically Encoded Probes for Sensing Macromolecular Crowding. Biophys J 2017; 112:1929-1939. [PMID: 28494963 DOI: 10.1016/j.bpj.2017.04.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 03/27/2017] [Accepted: 04/04/2017] [Indexed: 10/19/2022] Open
Abstract
Cells are highly crowded with proteins and polynucleotides. Any reaction that depends on the available volume can be affected by macromolecular crowding, but the effects of crowding in cells are complex and difficult to track. Here, we present a set of Förster resonance energy transfer (FRET)-based crowding-sensitive probes and investigate the role of the linker design. We investigate the sensors in vitro and in vivo and by molecular dynamics simulations. We find that in vitro all the probes can be compressed by crowding, with a magnitude that increases with the probe size, the crowder concentration, and the crowder size. We capture the role of the linker in a heuristic scaling model, and we find that compression is a function of size of the probe and volume fraction of the crowder. The FRET changes observed in Escherichia coli are more complicated, where FRET-increases and scaling behavior are observed solely with probes that contain the helices in the linker. The probe with the highest sensitivity to crowding in vivo yields the same macromolecular volume fractions as previously obtained from cell dry weight. The collection of new probes provides more detailed readouts on the macromolecular crowding than a single sensor.
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Affiliation(s)
- Boqun Liu
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Christoffer Åberg
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Floris J van Eerden
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Siewert J Marrink
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Bert Poolman
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands.
| | - Arnold J Boersma
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands.
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63
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Gtari W, Bey H, Aschi A, Bitri L, Othman T. Impact of macromolecular crowding on structure and properties of pepsin and trypsin. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2017; 72:98-105. [DOI: 10.1016/j.msec.2016.11.046] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 09/24/2016] [Accepted: 11/13/2016] [Indexed: 11/25/2022]
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64
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Fonin AV, Silonov SA, Sitdikova AK, Kuznetsova IM, Uversky VN, Turoverov KK. Structure and Conformational Properties of d-Glucose/d-Galactose-Binding Protein in Crowded Milieu. Molecules 2017; 22:molecules22020244. [PMID: 28178192 PMCID: PMC6155729 DOI: 10.3390/molecules22020244] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 01/26/2017] [Accepted: 01/29/2017] [Indexed: 11/18/2022] Open
Abstract
Conformational changes of d-glucose/d-galactose-binding protein (GGBP) were studied under molecular crowding conditions modeled by concentrated solutions of polyethylene glycols (PEG-12000, PEG-4000, and PEG-600), Ficoll-70, and Dextran-70, addition of which induced noticeable structural changes in the GGBP molecule. All PEGs promoted compaction of GGBP and lead to the increase in ordering of its structure. Concentrated solutions of PEG-12000 and PEG-4000 caused GGBP aggregation. Although Ficoll-70 and Dextran-70 also promoted increase in the GGBP ordering, the structural outputs were different for different crowders. For example, in comparison with the GGBP in buffer, the intrinsic fluorescence spectrum of this protein was shifted to short-wave region in the presence of PEGs but was red-shifted in the presence of Ficoll-70 and Dextran-70. It was hypothesized that this difference could be due to the specific interaction of GGBP with the sugar-based polymers (Ficoll-70 and Dextran-70), indicating that protein can adopt different conformations in solutions containing molecular crowders of different chemical nature. It was also shown that all tested crowding agents were able to stabilize GGBP structure shifting the GGBP guanidine hydrochloride (GdnHCl)-induced unfolding curves to higher denaturant concentrations, but their stabilization capabilities did not depend on the hydrodynamic dimensions of the polymers molecules. Refolding of GGBP was complicated by protein aggregation in all tested solutions of crowding agents. The lowest yield of refolded protein was achieved in the highly concentrated solutions of PEG-12000. These data support the previous notion that the influence of macromolecular crowders on proteins is rather complex phenomenon that extends beyond the excluded volume effects.
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Affiliation(s)
- Alexander V Fonin
- Institute of Cytology of the Russian Academy of Sciences, Laboratory of Structural Dynamics, Stability and Folding of Proteins, Tikhoretsky av. 4, St. Petersburg 197046, Russia.
| | - Sergey A Silonov
- Institute of Cytology of the Russian Academy of Sciences, Laboratory of Structural Dynamics, Stability and Folding of Proteins, Tikhoretsky av. 4, St. Petersburg 197046, Russia.
- Saint-Petersburg Technological Institute (Technical University), Moskovsky av. 26, Saint-Petersburg 190013, Russia.
| | - Asiya K Sitdikova
- Institute of Cytology of the Russian Academy of Sciences, Laboratory of Structural Dynamics, Stability and Folding of Proteins, Tikhoretsky av. 4, St. Petersburg 197046, Russia.
- Department of Biophysics, St. Petersburg State Polytechnical University, Polytechnicheskaya av. 29, St. Petersburg 195251, Russia.
| | - Irina M Kuznetsova
- Institute of Cytology of the Russian Academy of Sciences, Laboratory of Structural Dynamics, Stability and Folding of Proteins, Tikhoretsky av. 4, St. Petersburg 197046, Russia.
| | - Vladimir N Uversky
- Institute of Cytology of the Russian Academy of Sciences, Laboratory of Structural Dynamics, Stability and Folding of Proteins, Tikhoretsky av. 4, St. Petersburg 197046, Russia.
- Department of Molecular Medicine and Byrd Alzheimer's Research Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA.
| | - Konstantin K Turoverov
- Institute of Cytology of the Russian Academy of Sciences, Laboratory of Structural Dynamics, Stability and Folding of Proteins, Tikhoretsky av. 4, St. Petersburg 197046, Russia.
- Department of Biophysics, St. Petersburg State Polytechnical University, Polytechnicheskaya av. 29, St. Petersburg 195251, Russia.
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65
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Shahid S, Hassan MI, Islam A, Ahmad F. Size-dependent studies of macromolecular crowding on the thermodynamic stability, structure and functional activity of proteins: in vitro and in silico approaches. Biochim Biophys Acta Gen Subj 2017; 1861:178-197. [DOI: 10.1016/j.bbagen.2016.11.014] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 11/09/2016] [Accepted: 11/10/2016] [Indexed: 11/27/2022]
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66
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Biswas S, Mukherjee SK, Chowdhury PK. Crowder-Induced Rigidity in a Multidomain Protein: Insights from Solvation. J Phys Chem B 2016; 120:12501-12510. [DOI: 10.1021/acs.jpcb.6b10478] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Saikat Biswas
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Sanjib Kumar Mukherjee
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Pramit Kumar Chowdhury
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
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67
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Wu Y, Teng N, Li S. Effects of macromolecular crowding and osmolyte on human Tau fibrillation. Int J Biol Macromol 2016; 90:27-36. [DOI: 10.1016/j.ijbiomac.2015.11.091] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 11/13/2015] [Accepted: 11/29/2015] [Indexed: 10/22/2022]
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68
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Yu T, Zhu Y, He Z, Chen SJ. Predicting Molecular Crowding Effects in Ion-RNA Interactions. J Phys Chem B 2016; 120:8837-44. [PMID: 27490487 DOI: 10.1021/acs.jpcb.6b05625] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
We develop a new statistical mechanical model to predict the molecular crowding effects in ion-RNA interactions. By considering discrete distributions of the crowders, the model can treat the main crowder-induced effects, such as the competition with ions for RNA binding, changes of electrostatic interaction due to crowder-induced changes in the dielectric environment, and changes in the nonpolar hydration state of the crowder-RNA system. To enhance the computational efficiency, we sample the crowder distribution using a hybrid approach: For crowders in the close vicinity of RNA surface, we sample their discrete distributions; for crowders in the bulk solvent away from the RNA surface, we use a continuous mean-field distribution for the crowders. Moreover, using the tightly bound ion (TBI) model, we account for ion fluctuation and correlation effects in the calculation for ion-RNA interactions. Applications of the model to a variety of simple RNA structures such as RNA helices show a crowder-induced increase in free energy and decrease in ion binding. Such crowding effects tend to contribute to the destabilization of RNA structure. Further analysis indicates that these effects are associated with the crowder-ion competition in RNA binding and the effective decrease in the dielectric constant. This simple ion effect model may serve as a useful framework for modeling more realistic crowders with larger, more complex RNA structures.
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Affiliation(s)
- Tao Yu
- Department of Physics, Department of Biochemistry, and Informatics Institute, University of Missouri , Columbia, Missouri 65211, United States.,Department of Physics, Jianghan University , Wuhan, Hubei 430056, China
| | - Yuhong Zhu
- Department of Physics, Department of Biochemistry, and Informatics Institute, University of Missouri , Columbia, Missouri 65211, United States.,Department of Physics, Hangzhou Normal University , Hangzhou, Zhejiang 310036, China
| | - Zhaojian He
- Department of Physics, Department of Biochemistry, and Informatics Institute, University of Missouri , Columbia, Missouri 65211, United States
| | - Shi-Jie Chen
- Department of Physics, Department of Biochemistry, and Informatics Institute, University of Missouri , Columbia, Missouri 65211, United States
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69
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Kadumuri RV, Gullipalli J, Subramanian S, Jaipuria G, Atreya HS, Vadrevu R. Crowding interactions perturb structure and stability by destabilizing the stable core of the α-subunit of tryptophan synthase. FEBS Lett 2016; 590:2096-105. [PMID: 27311646 DOI: 10.1002/1873-3468.12259] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 06/06/2016] [Accepted: 06/13/2016] [Indexed: 11/12/2022]
Abstract
The consequences of crowding derived from relatively small and intrinsically disordered proteins are not clear yet. We report the effect of ficoll-70 on the structure and stability of native and partially folded states of the 29 kDa alpha subunit of tryptophan synthase (αTS). Overall, combining the changes in the circular dichroism and fluorescence spectra, in conjunction with the gradual loss of cooperativity under urea denaturation in the presence of increasing amounts of ficoll, it may be concluded that the crowding agent perturbs not only the native state but also the partially folded state of αTS. Importantly, NMR data indicate that ficoll interacts with the residues that constitute the stable core of the protein thus shedding light on the origin of the observed perturbation.
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Affiliation(s)
- Rajashekar Varma Kadumuri
- Department of Biological Sciences, Birla Institute of Technology & Science-Pilani, Hyderabad Campus, Hyderabad, India
| | - Jagadeesh Gullipalli
- Department of Biological Sciences, Birla Institute of Technology & Science-Pilani, Hyderabad Campus, Hyderabad, India
| | - SriVidya Subramanian
- Department of Biological Sciences, Birla Institute of Technology & Science-Pilani, Hyderabad Campus, Hyderabad, India
| | - Garima Jaipuria
- NMR Research Centre, Indian Institute of Science, Bangalore, India
| | | | - Ramakrishna Vadrevu
- Department of Biological Sciences, Birla Institute of Technology & Science-Pilani, Hyderabad Campus, Hyderabad, India
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70
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Stepanenko OV, Roginskii DO, Stepanenko OV, Kuznetsova IM, Uversky VN, Turoverov KK. Structure and stability of recombinant bovine odorant-binding protein: III. Peculiarities of the wild type bOBP unfolding in crowded milieu. PeerJ 2016; 4:e1642. [PMID: 27114858 PMCID: PMC4841217 DOI: 10.7717/peerj.1642] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 01/08/2016] [Indexed: 11/23/2022] Open
Abstract
Contrary to the majority of the members of the lipocalin family, which are stable monomers with the specific OBP fold (a β-barrel consisting of a 8-stranded anti-parallel β-sheet followed by a short α-helical segment, a ninth β-strand, and a disordered C-terminal tail) and a conserved disulfide bond, bovine odorant-binding protein (bOBP) does not have such a disulfide bond and forms a domain-swapped dimer that involves crossing the α-helical region from each monomer over the β-barrel of the other monomer. Furthermore, although natural bOBP isolated from bovine tissues exists as a stable domain-swapped dimer, recombinant bOBP has decreased dimerization potential and therefore exists as a mixture of monomeric and dimeric variants. In this article, we investigated the effect model crowding agents of similar chemical nature but different molecular mass on conformational stability of the recombinant bOBP. These experiments were conducted in order to shed light on the potential influence of model crowded environment on the unfolding-refolding equilibrium. To this end, we looked at the influence of PEG-600, PEG-4000, and PEG-12000 in concentrations of 80, 150, and 300 mg/mL on the equilibrium unfolding and refolding transitions induced in the recombinant bOBP by guanidine hydrochloride. We are showing here that the effect of crowding agents on the structure and conformational stability of the recombinant bOBP depends on the size of the crowder, with the smaller crowding agents being more effective in the stabilization of the bOBP native dimeric state against the guanidine hydrochloride denaturing action. This effect of the crowding agents is concentration dependent, with the high concentrations of the agents being more effective.
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Affiliation(s)
- Olga V. Stepanenko
- Laboratory of structural dynamics, stability and folding of proteins, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
| | - Denis O. Roginskii
- Laboratory of structural dynamics, stability and folding of proteins, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
| | - Olesya V. Stepanenko
- Laboratory of structural dynamics, stability and folding of proteins, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
| | - Irina M. Kuznetsova
- Laboratory of structural dynamics, stability and folding of proteins, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
| | - Vladimir N. Uversky
- Laboratory of structural dynamics, stability and folding of proteins, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
- Department of Molecular Medicine, University of South Florida, United States
| | - Konstantin K. Turoverov
- Laboratory of structural dynamics, stability and folding of proteins, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
- Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russia
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71
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Paul SS, Sil P, Chakraborty R, Haldar S, Chattopadhyay K. Molecular Crowding Affects the Conformational Fluctuations, Peroxidase Activity, and Folding Landscape of Yeast Cytochrome c. Biochemistry 2016; 55:2332-43. [DOI: 10.1021/acs.biochem.6b00053] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Simanta Sarani Paul
- Protein
Folding and Dynamics Laboratory, Structural Biology and Bioinformatics
Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S. C.
Mullick Road, Kolkata 700032, India
| | - Pallabi Sil
- Protein
Folding and Dynamics Laboratory, Structural Biology and Bioinformatics
Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S. C.
Mullick Road, Kolkata 700032, India
| | - Ritobrita Chakraborty
- Protein
Folding and Dynamics Laboratory, Structural Biology and Bioinformatics
Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S. C.
Mullick Road, Kolkata 700032, India
| | - Shubhasis Haldar
- Department
of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz
18, 82152 Martinsried, Germany
| | - Krishnananda Chattopadhyay
- Protein
Folding and Dynamics Laboratory, Structural Biology and Bioinformatics
Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S. C.
Mullick Road, Kolkata 700032, India
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72
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Macdonald B, McCarley S, Noeen S, van Giessen AE. β-Hairpin Crowding Agents Affect α-Helix Stability in Crowded Environments. J Phys Chem B 2016; 120:650-9. [DOI: 10.1021/acs.jpcb.5b10575] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Bryanne Macdonald
- Department of Chemistry, Mount Holyoke College, South Hadley, Massachusetts 01075, United States
| | - Shannon McCarley
- Department of Chemistry, Mount Holyoke College, South Hadley, Massachusetts 01075, United States
| | - Sundus Noeen
- Department of Chemistry, Mount Holyoke College, South Hadley, Massachusetts 01075, United States
| | - Alan E. van Giessen
- Department of Chemistry, Mount Holyoke College, South Hadley, Massachusetts 01075, United States
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73
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Stepanenko OV, Povarova OI, Sulatskaya AI, Ferreira LA, Zaslavsky BY, Kuznetsova IM, Turoverov KK, Uversky VN. Protein unfolding in crowded milieu: what crowding can do to a protein undergoing unfolding? J Biomol Struct Dyn 2016; 34:2155-70. [PMID: 26474212 DOI: 10.1080/07391102.2015.1109554] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The natural environment of a protein inside a cell is characterized by the almost complete lack of unoccupied space, limited amount of free water, and the tightly packed crowd of various biological macromolecules, such as proteins, nucleic acids, polysaccharides, and complexes thereof. This extremely crowded natural milieu is poorly mimicked by slightly salted aqueous solutions containing low concentrations of a protein of interest. The accepted practice is to model crowded environments by adding high concentrations of various polymers that serve as model "crowding agents" to the solution of a protein of interest. Although studies performed under these model conditions revealed that macromolecular crowding might have noticeable influence on various aspects related to the protein structure, function, folding, conformational stability, and aggregation propensity, the complete picture describing conformational behavior of a protein under these conditions is missing as of yet. Furthermore, there is an accepted belief that the conformational stability of globular proteins increases in the presence crowding agents due to the excluded volume effects. The goal of this study was to conduct a systematic analysis of the effect of high concentrations of PEG-8000 and Dextran-70 on the unfolding behavior of eleven globular proteins belonging to different structural classes.
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Affiliation(s)
- Olga V Stepanenko
- a Laboratory of Structural Dynamics, Stability and Folding of Proteins , Institute of Cytology, Russian Academy of Sciences , St. Petersburg , Russia
| | - Olga I Povarova
- a Laboratory of Structural Dynamics, Stability and Folding of Proteins , Institute of Cytology, Russian Academy of Sciences , St. Petersburg , Russia
| | - Anna I Sulatskaya
- a Laboratory of Structural Dynamics, Stability and Folding of Proteins , Institute of Cytology, Russian Academy of Sciences , St. Petersburg , Russia
| | - Luisa A Ferreira
- b Cleveland Diagnostics , 3615 Superior Ave., Suite 4407B, Cleveland , OH 44114 , USA
| | - Boris Y Zaslavsky
- b Cleveland Diagnostics , 3615 Superior Ave., Suite 4407B, Cleveland , OH 44114 , USA
| | - Irina M Kuznetsova
- a Laboratory of Structural Dynamics, Stability and Folding of Proteins , Institute of Cytology, Russian Academy of Sciences , St. Petersburg , Russia
| | - Konstantin K Turoverov
- a Laboratory of Structural Dynamics, Stability and Folding of Proteins , Institute of Cytology, Russian Academy of Sciences , St. Petersburg , Russia.,c Department of Biophysics , Peter the Great St. Petersburg Polytechnic University , St. Petersburg , 195251 , Russia
| | - Vladimir N Uversky
- a Laboratory of Structural Dynamics, Stability and Folding of Proteins , Institute of Cytology, Russian Academy of Sciences , St. Petersburg , Russia.,d Department of Molecular Medicine and Byrd Alzheimer's Research Institute, Morsani College of Medicine , University of South Florida , Tampa , FL 33612 , USA
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74
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Kumar R, Sharma D, Jain R, Kumar S, Kumar R. Role of macromolecular crowding and salt ions on the structural-fluctuation of a highly compact configuration of carbonmonoxycytochrome c. Biophys Chem 2015; 207:61-73. [DOI: 10.1016/j.bpc.2015.09.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 09/04/2015] [Accepted: 09/06/2015] [Indexed: 11/25/2022]
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75
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Niwa T, Sugimoto R, Watanabe L, Nakamura S, Ueda T, Taguchi H. Large-scale analysis of macromolecular crowding effects on protein aggregation using a reconstituted cell-free translation system. Front Microbiol 2015; 6:1113. [PMID: 26500644 PMCID: PMC4597115 DOI: 10.3389/fmicb.2015.01113] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 09/25/2015] [Indexed: 11/21/2022] Open
Abstract
Proteins must fold into their native structures in the crowded cellular environment, to perform their functions. Although such macromolecular crowding has been considered to affect the folding properties of proteins, large-scale experimental data have so far been lacking. Here, we individually translated 142 Escherichia coli cytoplasmic proteins using a reconstituted cell-free translation system in the presence of macromolecular crowding reagents (MCRs), Ficoll 70 or dextran 70, and evaluated the aggregation propensities of 142 proteins. The results showed that the MCR effects varied depending on the proteins, although the degree of these effects was modest. Statistical analyses suggested that structural parameters were involved in the effects of the MCRs. Our dataset provides a valuable resource to understand protein folding and aggregation inside cells.
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Affiliation(s)
- Tatsuya Niwa
- Department of Biomolecular Engineering, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology Yokohama, Japan
| | - Ryota Sugimoto
- Department of Biomolecular Engineering, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology Yokohama, Japan
| | - Lisa Watanabe
- Department of Biomolecular Engineering, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology Yokohama, Japan
| | - Shugo Nakamura
- Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo Tokyo, Japan
| | - Takuya Ueda
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo Chiba, Japan
| | - Hideki Taguchi
- Department of Biomolecular Engineering, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology Yokohama, Japan
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76
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Shahid S, Ahmad F, Hassan MI, Islam A. Relationship between protein stability and functional activity in the presence of macromolecular crowding agents alone and in mixture: An insight into stability-activity trade-off. Arch Biochem Biophys 2015; 584:42-50. [PMID: 26325080 DOI: 10.1016/j.abb.2015.08.015] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 08/19/2015] [Accepted: 08/23/2015] [Indexed: 12/25/2022]
Abstract
The cellular environment is crowded with different kinds of molecules with varying sizes, shapes and compositions. Most of the experiments studying the nature and behaviour of a protein have been done on the isolated protein in dilute buffer solutions which actually do not imitate the in vivo situation. To understand the consequences of such crowded environment, we investigated the effect of macromolecular crowding on the stability and activity of hen egg white lysozyme. Two crowding agents, dextran 70 and ficoll 70 which have different shapes and composition, have been employed in this study. To mimic the cellular condition from physiological point of view, the effect of mixtures of both the crowding agents has been also studied. The results indicate that owing to volume exclusion, lysozyme is stabilized while its activity decays with the increasing concentration of both the crowders elucidating the hypothesis of stability-activity trade-off. Mixed macromolecular crowding exerts greater effect than the sum of constituent crowding agents (dextran 70 and ficoll 70).
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Affiliation(s)
- Sumra Shahid
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, Jamia Nagar, New Delhi 110025, India
| | - Faizan Ahmad
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, Jamia Nagar, New Delhi 110025, India
| | - Md Imtaiyaz Hassan
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, Jamia Nagar, New Delhi 110025, India
| | - Asimul Islam
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, Jamia Nagar, New Delhi 110025, India.
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77
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Mikaelsson T, Ådén J, Wittung-Stafshede P, Johansson LBÅ. Macromolecular crowding effects on two homologs of ribosomal protein s16: protein-dependent structural changes and local interactions. Biophys J 2015; 107:401-410. [PMID: 25028882 DOI: 10.1016/j.bpj.2014.05.038] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Revised: 05/28/2014] [Accepted: 05/30/2014] [Indexed: 11/30/2022] Open
Abstract
Proteins function in cellular environments that are crowded with biomolecules, and in this reduced available space, their biophysical properties may differ from those observed in dilute solutions in vitro. Here, we investigated the effects of a synthetic macromolecular crowding agent, dextran 20, on the folded states of hyperthermophilic (S16Thermo) and mesophilic (S16Meso) homologs of the ribosomal protein S16. As expected for an excluded-volume effect, the resistance of the mesophilic protein to heat-induced unfolding increased in the presence of dextran 20, and chemical denaturation experiments at different fixed temperatures showed the macromolecular crowding effect to be temperature-independent. Förster resonance energy transfer experiments show that intramolecular distances between an intrinsic Trp residue and BODIPY-labeled S16Meso depend on the level of the crowding agent. The BODIPY group was attached at three specific positions in S16Meso, allowing measurements of three intraprotein distances. All S16Meso variants exhibited a decrease in the average Trp-BODIPY distance at up to 100 mg/mL dextran 20, whereas the changes in distance became anisotropic (one distance increased, two distances decreased) at higher dextran concentrations. In contrast, the two S16Thermo mutants did not show any changes in Trp-BODIPY distances upon increase of dextran 20 concentrations. It should be noted that the fluorescence quantum yields and lifetimes of BODIPY attached to the two S16 homologs decreased gradually in the presence of dextran 20. To investigate the origin of this decrease, we studied the BODIPY quantum yield in three protein variants in the presence of a tyrosine-labeled dextran. The experiments revealed distinct tyrosine quenching behaviors of BODIPY in the three variants, suggesting a dynamic local interaction between dextran and one particular S16 variant.
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Affiliation(s)
| | - Jörgen Ådén
- Department of Chemistry, Umeå University, Umeå, Sweden
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78
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What macromolecular crowding can do to a protein. Int J Mol Sci 2014; 15:23090-140. [PMID: 25514413 PMCID: PMC4284756 DOI: 10.3390/ijms151223090] [Citation(s) in RCA: 355] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 12/04/2014] [Accepted: 12/05/2014] [Indexed: 01/17/2023] Open
Abstract
The intracellular environment represents an extremely crowded milieu, with a limited amount of free water and an almost complete lack of unoccupied space. Obviously, slightly salted aqueous solutions containing low concentrations of a biomolecule of interest are too simplistic to mimic the “real life” situation, where the biomolecule of interest scrambles and wades through the tightly packed crowd. In laboratory practice, such macromolecular crowding is typically mimicked by concentrated solutions of various polymers that serve as model “crowding agents”. Studies under these conditions revealed that macromolecular crowding might affect protein structure, folding, shape, conformational stability, binding of small molecules, enzymatic activity, protein-protein interactions, protein-nucleic acid interactions, and pathological aggregation. The goal of this review is to systematically analyze currently available experimental data on the variety of effects of macromolecular crowding on a protein molecule. The review covers more than 320 papers and therefore represents one of the most comprehensive compendia of the current knowledge in this exciting area.
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79
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Goldenberg DP, Argyle B. Minimal effects of macromolecular crowding on an intrinsically disordered protein: a small-angle neutron scattering study. Biophys J 2014; 106:905-14. [PMID: 24559993 DOI: 10.1016/j.bpj.2013.12.003] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 11/26/2013] [Accepted: 12/02/2013] [Indexed: 01/04/2023] Open
Abstract
Small-angle neutron scattering was used to study the effects of macromolecular crowding by two globular proteins, i.e., bovine pancreatic trypsin inhibitor and equine metmyoglobin, on the conformational ensemble of an intrinsically disordered protein, the N protein of bacteriophage λ. The λ N protein was uniformly labeled with (2)H, and the concentrations of D2O in the samples were adjusted to match the neutron scattering contrast of the unlabeled crowding proteins, thereby masking their contribution to the scattering profiles. Scattering from the deuterated λ N was recorded for samples containing up to 0.12 g/mL bovine pancreatic trypsin inhibitor or 0.2 g/mL metmyoglobin. The radius of gyration of the uncrowded protein was estimated to be 30 Å and was found to be remarkably insensitive to the presence of crowders, varying by <2 Å for the highest crowder concentrations. The scattering profiles were also used to estimate the fractal dimension of λ N, which was found to be ∼1.8 in the absence or presence of crowders, indicative of a well-solvated and expanded random coil under all of the conditions examined. These results are contrary to the predictions of theoretical treatments and previous experimental studies demonstrating compaction of unfolded proteins by crowding with polymers such as dextran and Ficoll. A computational simulation suggests that some previous treatments may have overestimated the effective volumes of disordered proteins and the variation of these volumes within an ensemble. The apparent insensitivity of λ N to crowding may also be due in part to weak attractive interactions with the crowding proteins, which may compensate for the effects of steric exclusion.
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Affiliation(s)
| | - Brian Argyle
- Department of Biology, University of Utah, Salt Lake City, Utah
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80
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Jaganathan M, Dhathathreyan A. Conformational transitions of cytochrome c in sub-micron-sized capsules at air/buffer interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:11356-11365. [PMID: 25233344 DOI: 10.1021/la5024696] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
This work presents the design of sub-micron-sized capsules of Cytochrome c (cyt c) in the range 300-350 nm and the conformational transitions of the protein that occur when the films of these capsules spread at the air/buffer interface are subjected to repeated compression-expansion cycles. Steady state fluorescence, time-resolved fluorescence, and circular dichroic (CD) spectra have been used to study the highly compact native conformation (70% helicity) of the protein in the capsules and its stability has been analyzed using cyclic voltammetry. The capsules have been characterized using zeta sizer and high resolution transmission electron microscopy (HRTEM). Surface concentration-surface pressure (Γ-π) isotherms of the films of the capsules spread at air/buffer interface following compression-expansion show destabilizing effect on cyt c. FTIR and CD spectra of these films skimmed from the surface show that the protein transitions gradually from its native helical to an anomalous beta sheet aggregated state. This results from a competition between stabilizing hydrated polar segments of the protein in the capsule and destabilizing nonspecific hydrophobic interactions arising at the air/buffer interface. This 2D model could further our understanding of the spatial and temporal roles of proteins in confined spaces and also in the design of new drug delivery vehicles using proteins.
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81
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The effect of macromolecular crowding on the electrostatic component of barnase-barstar binding: a computational, implicit solvent-based study. PLoS One 2014; 9:e98618. [PMID: 24915485 PMCID: PMC4051634 DOI: 10.1371/journal.pone.0098618] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 05/05/2014] [Indexed: 02/02/2023] Open
Abstract
Macromolecular crowding within the cell can impact both protein folding and binding. Earlier models of cellular crowding focused on the excluded volume, entropic effect of crowding agents, which generally favors compact protein states. Recently, other effects of crowding have been explored, including enthalpically-related crowder–protein interactions and changes in solvation properties. In this work, we explore the effects of macromolecular crowding on the electrostatic desolvation and solvent-screened interaction components of protein–protein binding. Our simple model enables us to focus exclusively on the electrostatic effects of water depletion on protein binding due to crowding, providing us with the ability to systematically analyze and quantify these potentially intuitive effects. We use the barnase–barstar complex as a model system and randomly placed, uncharged spheres within implicit solvent to model crowding in an aqueous environment. On average, we find that the desolvation free energy penalties incurred by partners upon binding are lowered in a crowded environment and solvent-screened interactions are amplified. At a constant crowder density (fraction of total available volume occupied by crowders), this effect generally increases as the radius of model crowders decreases, but the strength and nature of this trend can depend on the water probe radius used to generate the molecular surface in the continuum model. In general, there is huge variation in desolvation penalties as a function of the random crowder positions. Results with explicit model crowders can be qualitatively similar to those using a lowered “effective” solvent dielectric to account for crowding, although the “best” effective dielectric constant will likely depend on multiple system properties. Taken together, this work systematically demonstrates, quantifies, and analyzes qualitative intuition-based insights into the effects of water depletion due to crowding on the electrostatic component of protein binding, and it provides an initial framework for future analyses.
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82
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Mittal S, Singh LR. Macromolecular crowding decelerates aggregation of a β-rich protein, bovine carbonic anhydrase: a case study. J Biochem 2014; 156:273-82. [PMID: 24917682 DOI: 10.1093/jb/mvu039] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The majority of in vitro investigations concerning protein aggregation have been performed in dilute systems, which poorly reflect the crowded in vivo scenario. Cell interior is highly crowded with soluble and insoluble macromolecules that alter macromolecular properties. Macromolecular crowding is known to enhance the rate and/or extent of protein aggregation. However, most of the understandings were derived from studies with α-rich or predominantly α-proteins. Indeed, α-proteins fold faster than β-proteins and conversion of α-helices to cross β-sheets are responsible for aggregate/amyloid formation. Therefore, it is important to investigate how macromolecular crowding affects the aggregation propensity of β-rich proteins. In this study, we investigated the effect of synthetic macromolecular crowders on bovine carbonic anhydrase (BCA, a β-rich protein) aggregation. In contrast to the effect of macromolecular crowding on α-rich proteins, BCA aggregation was observed to be reduced due to decrease in the population of aggregation-prone intermediates as a consequence of increased native state stability. In addition, the extent of aggregation was found to depend on the nature of the crowder under consideration. Combining the published data on α-proteins and this study, we conclude that macromolecular crowding can have opposite consequences on protein aggregation process depending on the fold type of the protein.
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Affiliation(s)
- Shruti Mittal
- Dr. B. R. Ambedkar Centre for Biomedical Research, University of Delhi, North Campus, New Delhi 110 007, India
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83
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Satyam A, Kumar P, Fan X, Gorelov A, Rochev Y, Joshi L, Peinado H, Lyden D, Thomas B, Rodriguez B, Raghunath M, Pandit A, Zeugolis D. Macromolecular crowding meets tissue engineering by self-assembly: a paradigm shift in regenerative medicine. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:3024-3034. [PMID: 24505025 DOI: 10.1002/adma.201304428] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Revised: 10/07/2013] [Indexed: 06/03/2023]
Abstract
MMC, the addition of inert polydispersed macromolecules in the culture media, effectively emulates the dense in vivo extracellular space, resulting in amplified deposition of ECM in vitro and subsequent production of cohesive, ECM-rich living substitutes.
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Affiliation(s)
- Abhigyan Satyam
- Network of Excellence for Functional Biomaterials (NFB), National University of Ireland Galway, (NUI Galway), Galway, Ireland
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84
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Spiga E, Abriata LA, Piazza F, Dal Peraro M. Dissecting the effects of concentrated carbohydrate solutions on protein diffusion, hydration, and internal dynamics. J Phys Chem B 2014; 118:5310-21. [PMID: 24773474 DOI: 10.1021/jp4126705] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
We present herein a thorough description of the effects of high glucose concentrations on the diffusion, hydration and internal dynamics of ubiquitin, as predicted from extensive molecular dynamics simulations on several systems described at fully atomistic level. We observe that the protein acts as a seed that speeds up the natural propensity of glucose to cluster at high concentration; the sugar molecules thus aggregate around the protein trapping it inside a dynamic cage. This process extensively dehydrates the protein surface, restricts the motions of the remaining water molecules, and drags the large-scale, collective motions of protein atoms slowing down the rate of exploration of the conformational space despite only a slight dampening of fast, local dynamics. We discuss how these effects could be relevant to the function of sugars as preservation agents in biological materials, and how crowding by small sticky molecules could modulate proteins across different reaction coordinates inside the cellular cytosol.
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Affiliation(s)
- Enrico Spiga
- Laboratory for Biomolecular Modeling, Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), and Swiss Institute of Bioinformatics (SIB), 1015 Lausanne, Switzerland
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85
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Christiansen A, Wittung-Stafshede P. Quantification of excluded volume effects on the folding landscape of Pseudomonas aeruginosa apoazurin in vitro. Biophys J 2014; 105:1689-99. [PMID: 24094410 DOI: 10.1016/j.bpj.2013.08.038] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 08/09/2013] [Accepted: 08/15/2013] [Indexed: 11/15/2022] Open
Abstract
Proteins fold and function inside cells that are crowded with macromolecules. Here, we address the role of the resulting excluded volume effects by in vitro spectroscopic studies of Pseudomonas aeruginosa apoazurin stability (thermal and chemical perturbations) and folding kinetics (chemical perturbation) as a function of increasing levels of crowding agents dextran (sizes 20, 40, and 70 kDa) and Ficoll 70. We find that excluded volume theory derived by Minton quantitatively captures the experimental effects when crowding agents are modeled as arrays of rods. This finding demonstrates that synthetic crowding agents are useful for studies of excluded volume effects. Moreover, thermal and chemical perturbations result in free energy effects by the presence of crowding agents that are identical, which shows that the unfolded state is energetically the same regardless of method of unfolding. This also underscores the two-state approximation for apoazurin's unfolding reaction and suggests that thermal and chemical unfolding experiments can be used in an interchangeable way. Finally, we observe increased folding speed and invariant unfolding speed for apoazurin in the presence of macromolecular crowding agents, a result that points to unfolded-state perturbations. Although the absolute magnitude of excluded volume effects on apoazurin is only on the order of 1-3 kJ/mol, differences of this scale may be biologically significant.
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86
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Abstract
Solutes excluded from macromolecules or colloids are known to drive depletion attractions. The established Asakura-Oosawa model, as well as subsequent theories aimed at explaining the effects of macromolecular crowding, attribute depletion forces to diminished hard-core excluded volume upon compaction, and hence predict depletion forces dominated by entropy. However, recent experiments measuring the effect of preferentially excluded solutes on protein folding and macromolecular association find these forces can also be enthalpic. We use simulations of macromolecular association in explicit binary cosolute-solvent mixtures, with solvent and cosolute intermolecular interactions that go beyond hard-cores, to show that not all cosolutes conform to the established entropically dominated model. We further demonstrate how the enthalpically dominated depletion forces that we find can be well described within an Asakura-Oosawa like model provided that the hard-core macromolecule-cosolute potential of mean force is augmented by a "soft" step-like repulsion.
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Affiliation(s)
- Liel Sapir
- Institute of Chemistry and The Fritz Haber Research Center, The Hebrew University, Jerusalem 91904, Israel
| | - Daniel Harries
- Institute of Chemistry and The Fritz Haber Research Center, The Hebrew University, Jerusalem 91904, Israel
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87
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Ådén J, Wittung-Stafshede P. Folding of an Unfolded Protein by Macromolecular Crowding in Vitro. Biochemistry 2014; 53:2271-7. [DOI: 10.1021/bi500222g] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jörgen Ådén
- Department of Chemistry, Umeå University, 90187 Umeå, Sweden
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88
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Cao C, Wang QB, Tang LJ, Ge BQ, Chen ZX, Deng SP. Chain-Length-Dependent Autocatalytic Hydrolysis of Fatty Acid Anhydrides in Polyethylene Glycol. J Phys Chem B 2014; 118:3461-8. [DOI: 10.1021/jp4125233] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Cao Cao
- College of Food & Biology Engineering, Zhejiang Gongshang University, Hangzhou, Zhejiang 310035, China
| | - Qing-Biao Wang
- College of Food & Biology Engineering, Zhejiang Gongshang University, Hangzhou, Zhejiang 310035, China
| | - Lin-Jun Tang
- College of Food & Biology Engineering, Zhejiang Gongshang University, Hangzhou, Zhejiang 310035, China
| | - Bing-Qiang Ge
- College of Food & Biology Engineering, Zhejiang Gongshang University, Hangzhou, Zhejiang 310035, China
| | - Zhong-Xiu Chen
- College of Food & Biology Engineering, Zhejiang Gongshang University, Hangzhou, Zhejiang 310035, China
| | - Shao-Ping Deng
- College of Food & Biology Engineering, Zhejiang Gongshang University, Hangzhou, Zhejiang 310035, China
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89
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Qin S, Zhou HX. Effects of Macromolecular Crowding on the Conformational Ensembles of Disordered Proteins. J Phys Chem Lett 2013; 4:10.1021/jz401817x. [PMID: 24312701 PMCID: PMC3846091 DOI: 10.1021/jz401817x] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Due to their conformational malleability, intrinsically disordered proteins (IDPs) are particularly susceptible to influences of crowded cellular environments. Here we report a computational study of the effects of macromolecular crowding on the conformational ensemble of a coarse-grained IDP model, by using two approaches. In one, the IDP is simulated along with the crowders; in the other, crowder-free simulations are postprocessed to predict the conformational ensembles under crowding. We found significant decreases in the radius of gyration of the IDP under crowding, and suggest repulsive interactions with crowders as a common cause for chain compaction in a number of experimental studies. The postprocessing approach accurately reproduced the conformational ensembles of the IDP in the direct simulations here, and holds enormous potential for realistic modeling of IDPs under crowding, by permitting thorough conformation sampling for the proteins even when they and the crowders are both represented at the all-atom level.
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Affiliation(s)
| | - Huan-Xiang Zhou
- Correspondence information: phone, (850) 645-1336; fax, (850) 644-7244; e-mail,
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90
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Qin S, Zhou HX. An FFT-based method for modeling protein folding and binding under crowding: benchmarking on ellipsoidal and all-atom crowders. J Chem Theory Comput 2013; 9. [PMID: 24187527 DOI: 10.1021/ct4005195] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
It is now well recognized that macromolecular crowding can exert significant effects on protein folding and binding stability. In order to calculate such effects in direct simulations of proteins mixed with bystander macromolecules, the latter (referred to as crowders) are usually modeled as spheres and the proteins represented at a coarse-grained level. Our recently developed postprocessing approach allows the proteins to be represented at the all-atom level but, for computational efficiency, has only been implemented for spherical crowders. Modeling crowder molecules in cellular environments and in vitro experiments as spheres may distort their effects on protein stability. Here we present a new method that is capable for treating aspherical crowders. The idea, borrowed from protein-protein docking, is to calculate the excess chemical potential of the proteins in crowded solution by fast Fourier transform (FFT). As the first application, we studied the effects of ellipsoidal crowders on the folding and binding free energies of all-atom proteins, and found, in agreement with previous direct simulations with coarse-grained protein models, that the aspherical crowders exert greater stabilization effects than spherical crowders of the same volume. Moreover, as demonstrated here, the FFT-based method has the important property that its computational cost does not increase strongly even when the level of details in representing the crowders is increased all the way to all-atom, thus significantly accelerating realistic modeling of protein folding and binding in cell-like environments.
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Affiliation(s)
- Sanbo Qin
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida
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91
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Feig M, Sugita Y. Reaching new levels of realism in modeling biological macromolecules in cellular environments. J Mol Graph Model 2013; 45:144-56. [PMID: 24036504 DOI: 10.1016/j.jmgm.2013.08.017] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Revised: 08/14/2013] [Accepted: 08/19/2013] [Indexed: 12/21/2022]
Abstract
An increasing number of studies are aimed at modeling cellular environments in a comprehensive and realistic fashion. A major challenge in these efforts is how to bridge spatial and temporal scales over many orders of magnitude. Furthermore, there are additional challenges in integrating different aspects ranging from questions about biomolecular stability in crowded environments to the description of reactive processes on cellular scales. In this review, recent studies with models of biomolecules in cellular environments at different levels of detail are discussed in terms of their strengths and weaknesses. In particular, atomistic models, implicit representations of cellular environments, coarse-grained and spheroidal models of biomolecules, as well as the inclusion of reactive processes via reaction-diffusion models are described. Furthermore, strategies for integrating the different models into a comprehensive description of cellular environments are discussed.
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Affiliation(s)
- Michael Feig
- Department of Biochemistry & Molecular Biology and Department of Chemistry, Michigan State University, 603 Wilson Road, BCH 218, East Lansing, MI 48824, United States; RIKEN Quantitative Biology Center, International Medical Device Alliance (IMDA) 6F, 1-6-5 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan.
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92
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Direct observation of protein unfolded state compaction in the presence of macromolecular crowding. Biophys J 2013; 104:694-704. [PMID: 23442920 DOI: 10.1016/j.bpj.2012.12.020] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 11/20/2012] [Accepted: 12/06/2012] [Indexed: 11/22/2022] Open
Abstract
Proteins fold and function in cellular environments that are crowded with other macromolecules. As a consequence of excluded volume effects, compact folded states of proteins should be indirectly stabilized due to destabilization of extended unfolded conformations. Here, we assess the role of excluded volume in terms of protein stability, structural dimensions and folding dynamics using a sugar-based crowding agent, dextran 20, and the small ribosomal protein S16 as a model system. To specifically address dimensions, we labeled the protein with BODIPY at two positions and measured Trp-BODIPY distances under different conditions. As expected, we found that dextran 20 (200 mg/ml) stabilized the variants against urea-induced unfolding. At conditions where the protein is unfolded, Förster resonance energy transfer measurements reveal that in the presence of dextran, the unfolded ensemble is more compact and there is residual structure left as probed by far-ultraviolet circular dichroism. In the presence of a crowding agent, folding rates are faster in the two-state regime, and at low denaturant concentrations, a kinetic intermediate is favored. Our study provides direct evidence for protein unfolded-state compaction in the presence of macromolecular crowding along with its energetic and kinetic consequences.
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93
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Abriata LA, Spiga E, Dal Peraro M. All-atom simulations of crowding effects on ubiquitin dynamics. Phys Biol 2013; 10:045006. [DOI: 10.1088/1478-3975/10/4/045006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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94
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Where soft matter meets living matter--protein structure, stability, and folding in the cell. Curr Opin Struct Biol 2013; 23:212-7. [PMID: 23474325 DOI: 10.1016/j.sbi.2013.02.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2012] [Revised: 02/08/2013] [Accepted: 02/13/2013] [Indexed: 01/06/2023]
Abstract
A protein is a biopolymer that self-assembles through the process of protein folding. A cell is a crowded space where the surrounding macromolecules of a protein can limit the number of ways of folding. These crowding macromolecules can also affect the shape and the size of a physically malleable, or 'soft, squishy', protein with regulatory purposes. In this review, we focus on the in silico approaches of coarse-grained molecular simulations that enable the investigation of protein folding in a cell-like environment. When these simulation results were compared with experimentally measured properties of a protein, such joint effort has yielded new ideas on the specific function of a protein in cells. We also highlighted the recent developments of computer modeling and simulations that encompass the importance of the shape of a macromolecule, the interactions between macromolecules, and the hydrodynamic interactions on the kinetics and thermodynamics of a protein in a high concentration of protein solution and in cytoplasmic environments.
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95
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Sarkar M, Li C, Pielak GJ. Soft interactions and crowding. Biophys Rev 2013; 5:187-194. [PMID: 28510157 DOI: 10.1007/s12551-013-0104-4] [Citation(s) in RCA: 183] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Accepted: 01/22/2013] [Indexed: 10/27/2022] Open
Abstract
The intracellular milieu is complex, heterogeneous and crowded-an environment vastly different from dilute solutions in which most biophysical studies are performed. The crowded cytoplasm excludes about a third of the volume available to macromolecules in dilute solution. This excluded volume is the sum of two parts: steric repulsions and chemical interactions, also called soft interactions. Until recently, most efforts to understand crowding have focused on steric repulsions. Here, we summarize the results and conclusions from recent studies on macromolecular crowding, emphasizing the contribution of soft interactions to the equilibrium thermodynamics of protein stability. Despite their non-specific and weak nature, the large number of soft interactions present under many crowded conditions can sometimes overcome the stabilizing steric, excluded volume effect.
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Affiliation(s)
- Mohona Sarkar
- Department of Chemistry, University of North Carolina-Chapel Hill, Chapel Hill, NC, 27599-3290, USA
| | - Conggang Li
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Molecular and Atomic Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071, People's Republic of China
| | - Gary J Pielak
- Department of Chemistry, University of North Carolina-Chapel Hill, Chapel Hill, NC, 27599-3290, USA. .,Department of Biochemistry and Biophysics, University of North Carolina-Chapel Hill, Chapel Hill, NC, 27599-3290, USA. .,UNC Lineberger Comprehensive Cancer Center, University of North Carolina-Chapel Hill, Chapel Hill, NC, 27599-3290, USA.
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96
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Christiansen A, Wang Q, Cheung MS, Wittung-Stafshede P. Effects of macromolecular crowding agents on protein folding in vitro and in silico. Biophys Rev 2013; 5:137-145. [PMID: 28510156 DOI: 10.1007/s12551-013-0108-0] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 01/31/2013] [Indexed: 01/24/2023] Open
Abstract
Proteins fold and function inside cells which are environments very different from that of dilute buffer solutions most often used in traditional experiments. The crowded milieu results in excluded-volume effects, increased bulk viscosity and amplified chances for inter-molecular interactions. These environmental factors have not been accounted for in most mechanistic studies of protein folding executed during the last decades. The question thus arises as to how these effects-present when polypeptides normally fold in vivo-modulate protein biophysics. To address excluded volume effects, we use synthetic macromolecular crowding agents, which take up significant volume but do not interact with proteins, in combination with strategically selected proteins and a range of equilibrium and time-resolved biophysical (spectroscopic and computational) methods. In this review, we describe key observations on macromolecular crowding effects on protein stability, folding and structure drawn from combined in vitro and in silico studies. As expected based on Minton's early predictions, many proteins (apoflavodoxin, VlsE, cytochrome c, and S16) became more thermodynamically stable (magnitude depends inversely on protein stability in buffer) and, unexpectedly, for apoflavodoxin and VlsE, the folded states changed both secondary structure content and, for VlsE, overall shape in the presence of macromolecular crowding. For apoflavodoxin and cytochrome c, which have complex kinetic folding mechanisms, excluded volume effects made the folding energy landscapes smoother (i.e., less misfolding and/or kinetic heterogeneity) than in buffer.
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Affiliation(s)
| | - Qian Wang
- Department of Physics, University of Houston, Houston, TX, 77204, USA
| | - Margaret S Cheung
- Department of Physics, University of Houston, Houston, TX, 77204, USA
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97
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Ultrafast electron transfer in riboflavin binding protein in macromolecular crowding of nano-sized micelle. Biochimie 2012; 94:2673-80. [DOI: 10.1016/j.biochi.2012.08.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2012] [Accepted: 08/06/2012] [Indexed: 11/20/2022]
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98
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Benton LA, Smith AE, Young GB, Pielak GJ. Unexpected Effects of Macromolecular Crowding on Protein Stability. Biochemistry 2012; 51:9773-5. [DOI: 10.1021/bi300909q] [Citation(s) in RCA: 173] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Laura A. Benton
- Department
of Chemistry, ‡Department of Biochemistry and Biophysics, and §Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel
Hill, North Carolina 27599, United States
| | - Austin E. Smith
- Department
of Chemistry, ‡Department of Biochemistry and Biophysics, and §Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel
Hill, North Carolina 27599, United States
| | - Gregory B. Young
- Department
of Chemistry, ‡Department of Biochemistry and Biophysics, and §Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel
Hill, North Carolina 27599, United States
| | - Gary J. Pielak
- Department
of Chemistry, ‡Department of Biochemistry and Biophysics, and §Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel
Hill, North Carolina 27599, United States
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99
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Abstract
Inside cells, the concentration of macromolecules can reach up to 400 g/L. In such crowded environments, proteins are expected to behave differently than in vitro. It has been shown that the stability and the folding rate of a globular protein can be altered by the excluded volume effect produced by a high density of macromolecules. However, macromolecular crowding effects on intrinsically disordered proteins (IDPs) are less explored. These proteins can be extremely dynamic and potentially sample a wide ensemble of conformations under non-denaturing conditions. The dynamic properties of IDPs are intimately related to the timescale of conformational exchange within the ensemble, which govern target recognition and how these proteins function. In this work, we investigated the macromolecular crowding effects on the dynamics of several IDPs by measuring the NMR spin relaxation parameters of three disordered proteins (ProTα, TC1, and α-synuclein) with different extents of residual structures. To aid the interpretation of experimental results, we also performed an MD simulation of ProTα. Based on the MD analysis, a simple model to correlate the observed changes in relaxation rates to the alteration in protein motions under crowding conditions was proposed. Our results show that 1) IDPs remain at least partially disordered despite the presence of high concentration of other macromolecules, 2) the crowded environment has differential effects on the conformational propensity of distinct regions of an IDP, which may lead to selective stabilization of certain target-binding motifs, and 3) the segmental motions of IDPs on the nanosecond timescale are retained under crowded conditions. These findings strongly suggest that IDPs function as dynamic structural ensembles in cellular environments.
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100
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Chen E, Christiansen A, Wang Q, Cheung MS, Kliger DS, Wittung-Stafshede P. Effects of macromolecular crowding on burst phase kinetics of cytochrome c folding. Biochemistry 2012; 51:9836-45. [PMID: 23145850 DOI: 10.1021/bi301324y] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Excluded volume and viscosity effects of crowding agents that mimic crowded conditions in vivo on "classical" burst phase folding kinetics of cytochrome c are assessed in vitro. Upon electron transfer-triggered folding of reduced cytochrome c, far-UV time-resolved circular dichroism (TRCD) is used to monitor folding under different conditions. Earlier work has shown that folding of reduced cytochrome c from the guanidinium hydrochloride-induced unfolded ensemble in dilute phosphate buffer involves kinetic partitioning: one fraction of molecules folds rapidly, on a time scale identical to that of reduction, while the remaining population folds more slowly. In the presence of 220 mg/mL dextran 70, a synthetic macromolecular crowding agent that occupies space but does not interact with proteins, the population of the fast folding step for cytochrome c is greatly reduced. Increasing the viscosity with sucrose to the same microviscosity exhibited by the dextran solution showed no significant decrease in the amplitude of the fast-folding phase of cytochrome c. Experiments show that the unfolded-state heme ligation remains bis-His in the presence of dextran 70, but coarse-grained simulations suggest that the unfolded-state ensemble becomes more compact in the presence of crowders. We conclude that excluded volume effects alter unfolded cytochrome c such that access to fast-folding conformations is reduced.
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Affiliation(s)
- Eefei Chen
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA
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