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Abstract
Cells of the vast majority of organisms are subject to temperature, pressure, pH, ionic strength, and other stresses. We discuss these effects in the light of protein folding and protein interactions in vitro, in complex environments, in cells, and in vivo. Protein phase diagrams provide a way of organizing different structural ensembles that occur under stress and how one can move among ensembles. Experiments that perturb biomolecules in vitro or in cells by stressing them have revealed much about the underlying forces that are competing to control protein stability, folding, and function. Two phenomena that emerge and serve to broadly classify effects of the cellular environment are crowding (mainly due to repulsive forces) and sticking (mainly due to attractive forces). The interior of cells is closely balanced between these emergent effects, and stress can tip the balance one way or the other. The free energy scale involved is small but significant on the scale of the "on/off switches" that control signaling in cells or of protein-protein association with a favorable function such as increased enzyme processivity. Quantitative tools from biophysical chemistry will play an important role in elucidating the world of crowding and sticking under stress.
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Affiliation(s)
- Mayank Boob
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Champaign, IL 61801, United States
| | - Yuhan Wang
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Champaign, IL 61801, United States
| | - Martin Gruebele
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Champaign, IL 61801, United States
- Department of Chemistry, Department of Physics, Center for the Physics of Living Cells, and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Champaign, IL 61801, United States
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2
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Luong TQ, Xu Y, Bründermann E, Leitner DM, Havenith M. Hydrophobic collapse induces changes in the collective protein and hydration low frequency modes. Chem Phys Lett 2016. [DOI: 10.1016/j.cplett.2016.02.036] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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3
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Fast-folding proteins under stress. Cell Mol Life Sci 2015; 72:4273-85. [PMID: 26231095 DOI: 10.1007/s00018-015-2002-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 07/07/2015] [Accepted: 07/24/2015] [Indexed: 10/23/2022]
Abstract
Proteins are subject to a variety of stresses in biological organisms, including pressure and temperature, which are the easiest stresses to simulate by molecular dynamics. We discuss the effect of pressure and thermal stress on very-fast-folding model proteins, whose in vitro folding can be fully simulated on computers and compared with experiments. We then discuss experiments that can be used to subject proteins to low- and high-temperature unfolding, as well as low- and high-pressure unfolding. Pressure and temperature are prototypical perturbations that illustrate how close many proteins are to instability, a property that cells can exploit to control protein function. We conclude by reviewing some recent in-cell experiments, and progress being made in simulating and measuring protein stability and function inside live cells.
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4
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Das P, Matysiak S. Direct Characterization of Hydrophobic Hydration during Cold and Pressure Denaturation. J Phys Chem B 2012; 116:5342-8. [DOI: 10.1021/jp211832c] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Payel Das
- Computational Biology Center, IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598, United States
| | - Silvina Matysiak
- Fischell Department of Bioengineering, University of Maryland, College Park, Maryland 20742,
United States
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Romero-Romero ML, Inglés-Prieto A, Ibarra-Molero B, Sanchez-Ruiz JM. Highly anomalous energetics of protein cold denaturation linked to folding-unfolding kinetics. PLoS One 2011; 6:e23050. [PMID: 21829584 PMCID: PMC3146537 DOI: 10.1371/journal.pone.0023050] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Accepted: 07/05/2011] [Indexed: 11/29/2022] Open
Abstract
Despite several careful experimental analyses, it is not yet clear whether protein cold-denaturation is just a “mirror image” of heat denaturation or whether it shows unique structural and energetic features. Here we report that, for a well-characterized small protein, heat denaturation and cold denaturation show dramatically different experimental energetic patterns. Specifically, while heat denaturation is endothermic, the cold transition (studied in the folding direction) occurs with negligible heat effect, in a manner seemingly akin to a gradual, second-order-like transition. We show that this highly anomalous energetics is actually an apparent effect associated to a large folding/unfolding free energy barrier and that it ultimately reflects kinetic stability, a naturally-selected trait in many protein systems. Kinetics thus emerges as an important factor linked to differential features of cold denaturation. We speculate that kinetic stabilization against cold denaturation may play a role in cold adaptation of psychrophilic organisms. Furthermore, we suggest that folding-unfolding kinetics should be taken into account when analyzing in vitro cold-denaturation experiments, in particular those carried out in the absence of destabilizing conditions.
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Affiliation(s)
- M. Luisa Romero-Romero
- Departamento de Quimica Fisica, Facultad de Ciencias, Universidad de Granada, Granada, Spain
| | - Alvaro Inglés-Prieto
- Departamento de Quimica Fisica, Facultad de Ciencias, Universidad de Granada, Granada, Spain
| | - Beatriz Ibarra-Molero
- Departamento de Quimica Fisica, Facultad de Ciencias, Universidad de Granada, Granada, Spain
| | - Jose M. Sanchez-Ruiz
- Departamento de Quimica Fisica, Facultad de Ciencias, Universidad de Granada, Granada, Spain
- * E-mail:
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6
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Bowman GR, Voelz VA, Pande VS. Atomistic folding simulations of the five-helix bundle protein λ(6−85). J Am Chem Soc 2011; 133:664-7. [PMID: 21174461 DOI: 10.1021/ja106936n] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein folding is a classic grand challenge that is relevant to numerous human diseases, such as protein misfolding diseases like Alzheimer’s disease. Solving the folding problem will ultimately require a combination of theory, simulation, and experiment, with theory and simulation providing an atomically detailed picture of both the thermodynamics and kinetics of folding and experimental tests grounding these models in reality. However, theory and simulation generally fall orders of magnitude short of biologically relevant time scales. Here we report significant progress toward closing this gap: an atomistic model of the folding of an 80-residue fragment of the λ repressor protein with explicit solvent that captures dynamics on a 10 milliseconds time scale. In addition, we provide a number of predictions that warrant further experimental investigation. For example, our model’s native state is a kinetic hub, and biexponential kinetics arises from the presence of many free-energy basins separated by barriers of different heights rather than a single low barrier along one reaction coordinate (the previously proposed incipient downhill folding scenario).
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Affiliation(s)
- Gregory R Bowman
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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7
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Liu F, Gao YG, Gruebele M. A survey of lambda repressor fragments from two-state to downhill folding. J Mol Biol 2010; 397:789-98. [PMID: 20138892 DOI: 10.1016/j.jmb.2010.01.071] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Revised: 01/25/2010] [Accepted: 01/26/2010] [Indexed: 12/23/2022]
Abstract
We survey the two-state to downhill folding transition by examining 20 lambda(6-85)* mutants that cover a wide range of stabilities and folding rates. We investigated four new lambda(6-85)* mutants designed to fold especially rapidly. Two were engineered using the core remodeling of Lim and Sauer, and two were engineered using Ferreiro et al.'s frustratometer. These proteins have probe-dependent melting temperatures as high as 80 degrees C and exhibit a fast molecular phase with the characteristic temperature dependence of the amplitude expected for downhill folding. The survey reveals a correlation between melting temperature and downhill folding previously observed for the beta-sheet protein WW domain. A simple model explains this correlation and predicts the melting temperature at which downhill folding becomes possible. An X-ray crystal structure with a 1.64-A resolution of a fast-folding mutant fragment shows regions of enhanced rigidity compared to the full wild-type protein.
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Affiliation(s)
- Feng Liu
- Center for Biophysics and Computational Biology, University of Illinois, Urbana, IL 61801, USA
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8
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DeCamp SJ, Naganathan AN, Waldauer SA, Bakajin O, Lapidus LJ. Direct observation of downhill folding of lambda-repressor in a microfluidic mixer. Biophys J 2009; 97:1772-7. [PMID: 19751683 DOI: 10.1016/j.bpj.2009.07.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2009] [Revised: 07/08/2009] [Accepted: 07/13/2009] [Indexed: 11/19/2022] Open
Abstract
The protein lambda(6-85) has been implicated in barrierless folding by observations of kinetic relaxation after nanosecond T-jump. In this work we observed folding of this protein after dilution of a high denaturant in an ultrarapid microfluidic mixer at temperatures far below the thermal midpoint. The observations of total intensity and spectral shift of tryptophan fluorescence yielded distinctly different kinetics and activation energies. These results may be explained as diffusion on a low-barrier, one-dimensional, free-energy surface, with different probes having different sensitivities along the reaction coordinate. Additionally, we observed an extremely fast phase within the mixing time that was not observed by T-jump, suggesting that the ensemble of unfolded states populated at high denaturant is distinct from those accessible at high temperature.
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Affiliation(s)
- Stephen J DeCamp
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan, USA
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9
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Reaching the protein folding speed limit with large, sub-microsecond pressure jumps. Nat Methods 2009; 6:515-9. [PMID: 19483692 DOI: 10.1038/nmeth.1336] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2009] [Accepted: 04/13/2009] [Indexed: 11/08/2022]
Abstract
Biomolecules are highly pressure-sensitive, but their dynamics upon return to ambient pressure are often too fast to observe with existing approaches. We describe a sample-efficient method capable of large and very fast pressure drops (<1 nanomole, >2,500 atmospheres and <0.7 microseconds). We validated the method by fluorescence-detected refolding of a genetically engineered lambda repressor mutant from its pressure-denatured state. We resolved barrierless structure formation upon return to ambient pressure; we observed a 2.1 +/- 0.7 microsecond refolding time, which is very close to the 'speed limit' for proteins and much faster than the corresponding temperature-jump refolding of the same protein. The ability to experimentally perform a large and very fast pressure drop opens up a new region of the biomolecular energy landscape for atomic-level simulation.
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10
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Kim HJ. Research Using Energy Landscape. JOURNAL OF THE KOREAN CHEMICAL SOCIETY-DAEHAN HWAHAK HOE JEE 2007. [DOI: 10.5012/jkcs.2007.51.6.487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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11
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Dumont C, Matsumura Y, Kim SJ, Li J, Kondrashkina E, Kihara H, Gruebele M. Solvent-tuning the collapse and helix formation time scales of lambda(6-85)*. Protein Sci 2007; 15:2596-604. [PMID: 17075136 PMCID: PMC2242409 DOI: 10.1110/ps.062257406] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The lambda(6-85)(*) pseudo-wild type of lambda repressor fragment is a fast two-state folder (k(f) approximately 35 microsec(-1) at 58 degrees C). Previously, highly stable lambda(6-85)(*) mutants with k(f) > 30 microsec(-1) have been engineered to fold nearly or fully downhill. Stabilization of the native state by solvent tuning might also tune lambda(6-85)(*) away from two-state folding. We test this prediction by examining the folding thermodynamics and kinetics of lambda(6-85)(*) in a stabilizing solvent, 45% by weight aqueous ethylene glycol at -28 degrees C. Detection of kinetics by circular dichroism at 222 nm (sensitive to helix content) and small angle X-ray scattering (measuring the radius of gyration) shows that refolding from guanidine hydrochloride denatured conditions exhibits very different time scales for collapse and secondary structure formation: the two processes become decoupled. Collapse remains a low-barrier activated process, while the fastest of several secondary structure formation time scales approaches the downhill folding limit. Two-state folding of lambda(6-85)(*) is not a robust process.
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Affiliation(s)
- Charles Dumont
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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