1
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Glasgow A, Hobbs HT, Perry ZR, Wells ML, Marqusee S, Kortemme T. Ligand-specific changes in conformational flexibility mediate long-range allostery in the lac repressor. Nat Commun 2023; 14:1179. [PMID: 36859492 PMCID: PMC9977783 DOI: 10.1038/s41467-023-36798-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 02/17/2023] [Indexed: 03/03/2023] Open
Abstract
Biological regulation ubiquitously depends on protein allostery, but the regulatory mechanisms are incompletely understood, especially in proteins that undergo ligand-induced allostery with few structural changes. Here we used hydrogen-deuterium exchange with mass spectrometry (HDX/MS) to map allosteric effects in a paradigm ligand-responsive transcription factor, the lac repressor (LacI), in different functional states (apo, or bound to inducer, anti-inducer, and/or DNA). Although X-ray crystal structures of the LacI core domain in these states are nearly indistinguishable, HDX/MS experiments reveal widespread differences in flexibility. We integrate these results with modeling of protein-ligand-solvent interactions to propose a revised model for allostery in LacI, where ligand binding allosterically shifts the conformational ensemble as a result of distinct changes in the rigidity of secondary structures in the different states. Our model provides a mechanistic basis for the altered function of distal mutations. More generally, our approach provides a platform for characterizing and engineering protein allostery.
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Affiliation(s)
- Anum Glasgow
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA, 94158, USA.
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, 10032, USA.
| | - Helen T Hobbs
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Zion R Perry
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, 06511, USA
| | - Malcolm L Wells
- Department of Physics, Columbia University, New York, NY, 10032, USA
| | - Susan Marqusee
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, 94720, USA
- Department of Molecular & Cell Biology, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Tanja Kortemme
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA, 94158, USA
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2
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The folding and misfolding mechanisms of multidomain proteins. MEDICINE IN DRUG DISCOVERY 2022. [DOI: 10.1016/j.medidd.2022.100126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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3
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Cheng M, Qian Y, Xing Z, Zylstra GJ, Huang X. The low-nanomolar 4-nitrobenzoate-responsive repressor PnbX negatively regulates the actinomycete-derived 4-nitrobenzoate-degrading pnb locus. Environ Microbiol 2021; 23:7028-7041. [PMID: 34554625 DOI: 10.1111/1462-2920.15787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 09/17/2021] [Accepted: 09/20/2021] [Indexed: 11/29/2022]
Abstract
Nitroaromatic compounds pose severe threats to public health and environmental safety. Nitro group removal via ammonia release is an important strategy for bacterial detoxification of nitroaromatic compounds, such as the conversion of 4-nitrobenzoate (4-NBA) to protocatechuate by the bacterial pnb operon. In contrast to the LysR-family transcriptional regulator PnbR in proteobacteria, the actinomycete-derived pnb locus (4-NBA degradation structural genes) formed an operon with the TetR-family transcriptional regulator gene pnbX, implying that it has a distinct regulatory mechanism. Here, pnbBA from the actinomycete Nocardioides sp. strain LMS-CY was biochemically confirmed to express 4-NBA degradation enzymes, and pnbX was essential for inducible degradation of 4-NBA. Purified PnbX-6His could bind the promoter probe of the pnb locus in vitro, and 4-NBA prevented this binding. 4-NBA could bind PnbX at a 1:1 molar ratio with KD = 26.7 ± 4.2 nM. Low-nanomolar levels of 4-NBA induced the transcription of the pnb operon in strain LMS-CY. PnbX bound a palindromic sequence motif (5'-TTACGTTACA-N8 -TGTAACGTAA-3') that encompasses the pnb promoter. This study identified a TetR-family repressor for the actinomycete-derived pnb operon that recognizes 10-8 M 4-NBA as its ligand, implying that nitro group removal of nitroaromatic compounds may be especially important for actinomycetes.
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Affiliation(s)
- Minggen Cheng
- Department of Microbiology, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Yingying Qian
- Department of Microbiology, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Ziyu Xing
- Department of Microbiology, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Gerben J Zylstra
- Department of Biochemistry and Microbiology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ, USA
| | - Xing Huang
- Department of Microbiology, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
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4
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Groseclose TM, Rondon RE, Hersey AN, Milner PT, Kim D, Zhang F, Realff MJ, Wilson CJ. Biomolecular Systems Engineering: Unlocking the Potential of Engineered Allostery via the Lactose Repressor Topology. Annu Rev Biophys 2021; 50:303-321. [PMID: 33606944 DOI: 10.1146/annurev-biophys-090820-101708] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Allosteric function is a critical component of many of the parts used to construct gene networks throughout synthetic biology. In this review, we discuss an emerging field of research and education, biomolecular systems engineering, that expands on the synthetic biology edifice-integrating workflows and strategies from protein engineering, chemical engineering, electrical engineering, and computer science principles. We focus on the role of engineered allosteric communication as it relates to transcriptional gene regulators-i.e., transcription factors and corresponding unit operations. In this review, we (a) explore allosteric communication in the lactose repressor LacI topology, (b) demonstrate how to leverage this understanding of allostery in the LacI system to engineer non-natural BUFFER and NOT logical operations, (c) illustrate how engineering workflows can be used to confer alternate allosteric functions in disparate systems that share the LacI topology, and (d) demonstrate how fundamental unit operations can be directed to form combinational logical operations.
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Affiliation(s)
- Thomas M Groseclose
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA;
| | - Ronald E Rondon
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA;
| | - Ashley N Hersey
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA;
| | - Prasaad T Milner
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA;
| | - Dowan Kim
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA;
| | - Fumin Zhang
- School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Matthew J Realff
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA;
| | - Corey J Wilson
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA;
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5
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My journey in academia: things not on the CV. PURE APPL CHEM 2020. [DOI: 10.1515/pac-2019-0805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
I am a professor at Chalmers University of Technology in Sweden. I trained in chemistry in Sweden but went to the USA for my postdoc. I remained there for 12 years, being faculty at two American universities, before I returned to Sweden for a professorship in the northern city of Umeå. More recently, I returned to my alma mater Chalmers University of Technology in Gothenburg, where I have taken on senior leadership roles. On paper, my career trajectory looks straightforward, but there are many detrimental aspects and lucky coincidences that are not listed on my CV. Life in academia is never easy, and one is never ‘done’. But working in academia is wonderful, as it provides so much freedom and creativity, including being very accommodating towards having kids. Here, I will describe my own personal journey, with the hope of inspiring young women to follow their own path in academia. Yes, there is still bias against women in academia, but change is happening, and the many benefits of being an academic beat such drawbacks.
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6
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Wilson CJ, Bommarius AS, Champion JA, Chernoff YO, Lynn DG, Paravastu AK, Liang C, Hsieh MC, Heemstra JM. Biomolecular Assemblies: Moving from Observation to Predictive Design. Chem Rev 2018; 118:11519-11574. [PMID: 30281290 PMCID: PMC6650774 DOI: 10.1021/acs.chemrev.8b00038] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Biomolecular assembly is a key driving force in nearly all life processes, providing structure, information storage, and communication within cells and at the whole organism level. These assembly processes rely on precise interactions between functional groups on nucleic acids, proteins, carbohydrates, and small molecules, and can be fine-tuned to span a range of time, length, and complexity scales. Recognizing the power of these motifs, researchers have sought to emulate and engineer biomolecular assemblies in the laboratory, with goals ranging from modulating cellular function to the creation of new polymeric materials. In most cases, engineering efforts are inspired or informed by understanding the structure and properties of naturally occurring assemblies, which has in turn fueled the development of predictive models that enable computational design of novel assemblies. This Review will focus on selected examples of protein assemblies, highlighting the story arc from initial discovery of an assembly, through initial engineering attempts, toward the ultimate goal of predictive design. The aim of this Review is to highlight areas where significant progress has been made, as well as to outline remaining challenges, as solving these challenges will be the key that unlocks the full power of biomolecules for advances in technology and medicine.
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Affiliation(s)
- Corey J. Wilson
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Andreas S. Bommarius
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Julie A. Champion
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Yury O. Chernoff
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
- Laboratory of Amyloid Biology & Institute of Translational Biomedicine, St. Petersburg State University, St. Petersburg 199034, Russia
| | - David G. Lynn
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| | - Anant K. Paravastu
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Chen Liang
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| | - Ming-Chien Hsieh
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| | - Jennifer M. Heemstra
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
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7
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Fuglestad B, Stetz MA, Belnavis Z, Wand AJ. Solution NMR investigation of the response of the lactose repressor core domain dimer to hydrostatic pressure. Biophys Chem 2017; 231:39-44. [PMID: 28249763 DOI: 10.1016/j.bpc.2017.02.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Revised: 02/21/2017] [Accepted: 02/22/2017] [Indexed: 11/19/2022]
Abstract
Previous investigations of the sensitivity of the lac repressor to high-hydrostatic pressure have led to varying conclusions. Here high-pressure solution NMR spectroscopy is used to provide an atomic level view of the pressure induced structural transition of the lactose repressor regulatory domain (LacI* RD) bound to the ligand IPTG. As the pressure is raised from ambient to 3kbar the native state of the protein is converted to a partially unfolded form. Estimates of rotational correlation times using transverse optimized relaxation indicates that a monomeric state is never reached and that the predominate form of the LacI* RD is dimeric throughout this pressure change. Spectral analysis suggests that the pressure-induced transition is localized and is associated with a volume change of approximately -115mlmol-1 and an average pressure dependent change in compressibility of approximately 30mlmol-1kbar-1. In addition, a subset of resonances emerge at high-pressures indicating the presence of a non-native but folded alternate state.
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Affiliation(s)
- Brian Fuglestad
- Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania Perelman School of Medicine, 905 Stellar-Chance Laboratories, 422 Curie Blvd, Philadelphia, PA 19104-6059, USA
| | - Matthew A Stetz
- Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania Perelman School of Medicine, 905 Stellar-Chance Laboratories, 422 Curie Blvd, Philadelphia, PA 19104-6059, USA
| | - Zachary Belnavis
- Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania Perelman School of Medicine, 905 Stellar-Chance Laboratories, 422 Curie Blvd, Philadelphia, PA 19104-6059, USA
| | - A Joshua Wand
- Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania Perelman School of Medicine, 905 Stellar-Chance Laboratories, 422 Curie Blvd, Philadelphia, PA 19104-6059, USA.
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8
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Soner S, Ozbek P, Garzon JI, Ben-Tal N, Haliloglu T. DynaFace: Discrimination between Obligatory and Non-obligatory Protein-Protein Interactions Based on the Complex's Dynamics. PLoS Comput Biol 2015; 11:e1004461. [PMID: 26506003 PMCID: PMC4623975 DOI: 10.1371/journal.pcbi.1004461] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 07/08/2015] [Indexed: 12/31/2022] Open
Abstract
Protein-protein interfaces have been evolutionarily-designed to enable transduction between the interacting proteins. Thus, we hypothesize that analysis of the dynamics of the complex can reveal details about the nature of the interaction, and in particular whether it is obligatory, i.e., persists throughout the entire lifetime of the proteins, or not. Indeed, normal mode analysis, using the Gaussian network model, shows that for the most part obligatory and non-obligatory complexes differ in their decomposition into dynamic domains, i.e., the mobile elements of the protein complex. The dynamic domains of obligatory complexes often mix segments from the interacting chains, and the hinges between them do not overlap with the interface between the chains. In contrast, in non-obligatory complexes the interface often hinges between dynamic domains, held together through few anchor residues on one side of the interface that interact with their counterpart grooves in the other end. In automatic analysis, 117 of 139 obligatory (84.2%) and 203 of 246 non-obligatory (82.5%) complexes are correctly classified by our method: DynaFace. We further use DynaFace to predict obligatory and non-obligatory interactions among a set of 300 putative protein complexes. DynaFace is available at: http://safir.prc.boun.edu.tr/dynaface.
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Affiliation(s)
- Seren Soner
- Department of Computer Engineering and Polymer Research Center, Bogazici University, Istanbul, Turkey
| | - Pemra Ozbek
- Department of Bioengineering, Marmara University, Istanbul, Turkey
| | - Jose Ignacio Garzon
- Departments of Biochemistry and Molecular Biophysics and Systems Biology and Howard Hughes Medical Institute, Columbia University, New York, New York, United States of America
| | - Nir Ben-Tal
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Turkan Haliloglu
- Department of Chemical Engineering and Polymer Research Center, Bogazici University, Istanbul, Turkey
- * E-mail:
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9
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Howell SC, Richards DH, Mitch WA, Wilson CJ. Leveraging the Mechanism of Oxidative Decay for Adenylate Kinase to Design Structural and Functional Resistances. ACS Chem Biol 2015; 10:2393-404. [PMID: 26266833 DOI: 10.1021/acschembio.5b00431] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Characterization of the mechanisms underlying hypohalous acid (i.e., hypochlorous acid or hypobromous acid) degradation of proteins is important for understanding how the immune system deactivates pathogens during infections and damages human tissues during inflammatory diseases. Proteins are particularly important hypohalous acid reaction targets in pathogens and in host tissues, as evidenced by the detection of chlorinated and brominated oxidizable residues. While a significant amount of work has been conducted for reactions of hypohalous acids with a range of individual amino acids and small peptides, the assessment of oxidative decay in full-length proteins has lagged in comparison. The most rigorous test of our understanding of oxidative decay of proteins is the rational redesign of proteins with conferred resistances to the decay of structure and function. Toward this end, in this study, we experimentally determined a putative mechanism of oxidative decay using adenylate kinase as the model system. In turn, we leveraged this mechanism to rationally design new proteins and experimentally test each system for oxidative resistance to loss of structure and function. From our extensive assessment of secondary structure, protein hydrodynamics, and enzyme activity upon hypochlorous acid or hypobromous acid challenge, we have identified two key strategies for conferring structural and functional resistance, namely, the design of proteins (adenylate kinase enzymes) that are resistant to oxidation requires complementary consideration of protein stability and the modification (elimination) of certain oxidizable residues proximal to catalytic sites.
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Affiliation(s)
| | | | - William A. Mitch
- Department
of Civil and Environmental Engineering, Stanford University, Stanford, California 94305, United States
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10
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Anand P, Schug A, Wenzel W. Structure based design of protein linkers for zinc finger nuclease. FEBS Lett 2013; 587:3231-5. [PMID: 23994524 DOI: 10.1016/j.febslet.2013.08.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Revised: 08/05/2013] [Accepted: 08/12/2013] [Indexed: 12/18/2022]
Abstract
Zinc finger nucleases are a promising tool to edit DNA in many biological applications, in particular for gene knockout. Despite many efforts the number of genes that can be effectively targeted with ZFNs remains severely limited, as available constructs cannot address arbitrary gene sequences. Here, we develop a novel concept to significantly enhance the number of DNA sequences that can be targeted by ZFN. Using an efficient computational model, we provide an extensive library of possible linker molecules between individual zinc finger motifs in the construct that can skip up to 10 base pairs between adjacent zinc finger recognition sites in the DNA sequence, which increases the number of genes that can be efficiently targeted by more than an order of magnitude.
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Affiliation(s)
- Priya Anand
- Institute of Nanotechnology, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
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11
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Meyer S, Ramot R, Kishore Inampudi K, Luo B, Lin C, Amere S, Wilson CJ. Engineering alternate cooperative-communications in the lactose repressor protein scaffold. Protein Eng Des Sel 2013; 26:433-43. [DOI: 10.1093/protein/gzt013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
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12
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Ramot R, Kishore Inampudi K, Wilson CJ. Lactose Repressor Experimental Folding Landscape: Fundamental Functional Unit and Tetramer Folding Mechanisms. Biochemistry 2012; 51:7569-79. [DOI: 10.1021/bi300545f] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Roee Ramot
- Department
of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06511, United States
| | - Krishna Kishore Inampudi
- Department
of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06511, United States
| | - Corey J. Wilson
- Department
of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06511, United States
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511, United
States
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13
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Wang Y, Chu X, Suo Z, Wang E, Wang J. Multidomain protein solves the folding problem by multifunnel combined landscape: theoretical investigation of a Y-family DNA polymerase. J Am Chem Soc 2012; 134:13755-64. [PMID: 22827444 DOI: 10.1021/ja3045663] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Approximately three-fourths of eukaryotic proteins are composed of multiple independently folded domains. However, much of our understanding is based on single domain proteins or isolated domains whose studies directly lead to well-known energy landscape theory in which proteins fold by navigating through a funneled energy landscape toward native structure ensembles. The degrees of freedom for proteins with multiple domains are many orders of magnitude larger than that for single domain proteins. Now, the question arises: How do the multidomain proteins solve the "protein folding problem"? Here, we specifically address this issue by exploring the structure folding relationship of Sulfolobus solfataricus DNA polymerase IV (DPO4), a prototype Y-family DNA polymerase which contains a polymerase core consisting of a palm (P domain), a finger (F domain), and a thumb domain (T domain) in addition to a little finger domain (LF domain). The theoretical results are in good agreement with the experimental data and lead to several theoretical predictions. Finally, we propose that for rapid folding into well-defined conformations which carry out the biological functions, four-domain DPO4 employs a divide-and-conquer strategy, that is, combining multiple individual folding funnels into a single funnel (domains fold independently and then coalesce). In this way, the degrees of freedom for multidomain proteins are polynomial rather than exponential, and the conformational search process can be reduced effectively from a large to a smaller time scale.
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Affiliation(s)
- Yong Wang
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, 130022, PR China
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14
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Morris ER, Searle MS. Overview of protein folding mechanisms: experimental and theoretical approaches to probing energy landscapes. CURRENT PROTOCOLS IN PROTEIN SCIENCE 2012; Chapter 28:28.2.1-28.2.22. [PMID: 22470128 DOI: 10.1002/0471140864.ps2802s68] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
We present an overview of the current experimental and theoretical approaches to studying protein folding mechanisms, set against current models of the folding energy landscape. We describe how stability and folding kinetics can be determined experimentally and how this data can be interpreted in terms of the characteristic features of various models from the simplest two-state pathway to a multi-state mechanism. We summarize the pros and cons of a range of spectroscopic methods for measuring folding rates and present a theoretical framework, coupled with protein engineering approaches, for elucidating folding mechanisms and structural features of folding transition states. A series of case studies are used to show how experimental kinetic data can be interpreted in the context of non-native interactions, populated intermediates, parallel folding pathways, and sequential transition states. We also show how computational methods now allow transient species of high energy, such as folding transition states, to be modeled on the basis of experimental Φ-value analysis derived from the effects of point mutations on folding kinetics.
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Affiliation(s)
- Elizabeth R Morris
- Centre for Biomolecular Sciences, School of Chemistry, University of Nottingham, Nottingham, United Kingdom
| | - Mark S Searle
- Centre for Biomolecular Sciences, School of Chemistry, University of Nottingham, Nottingham, United Kingdom
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15
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Haeusler AR, Goodson KA, Lillian TD, Wang X, Goyal S, Perkins NC, Kahn JD. FRET studies of a landscape of Lac repressor-mediated DNA loops. Nucleic Acids Res 2012; 40:4432-45. [PMID: 22307389 PMCID: PMC3378866 DOI: 10.1093/nar/gks019] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
DNA looping mediated by the Lac repressor is an archetypal test case for modeling protein and DNA flexibility. Understanding looping is fundamental to quantitative descriptions of gene expression. Systematic analysis of LacI•DNA looping was carried out using a landscape of DNA constructs with lac operators bracketing an A-tract bend, produced by varying helical phasings between operators and the bend. Fluorophores positioned on either side of both operators allowed direct Förster resonance energy transfer (FRET) detection of parallel (P1) and antiparallel (A1, A2) DNA looping topologies anchored by V-shaped LacI. Combining fluorophore position variant landscapes allows calculation of the P1, A1 and A2 populations from FRET efficiencies and also reveals extended low-FRET loops proposed to form via LacI opening. The addition of isopropyl-β-d-thio-galactoside (IPTG) destabilizes but does not eliminate the loops, and IPTG does not redistribute loops among high-FRET topologies. In some cases, subsequent addition of excess LacI does not reduce FRET further, suggesting that IPTG stabilizes extended or other low-FRET loops. The data align well with rod mechanics models for the energetics of DNA looping topologies. At the peaks of the predicted energy landscape for V-shaped loops, the proposed extended loops are more stable and are observed instead, showing that future models must consider protein flexibility.
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Affiliation(s)
- Aaron R Haeusler
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742-2021, USA
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16
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Chavarría M, Santiago C, Platero R, Krell T, Casasnovas JM, de Lorenzo V. Fructose 1-phosphate is the preferred effector of the metabolic regulator Cra of Pseudomonas putida. J Biol Chem 2011; 286:9351-9. [PMID: 21239488 DOI: 10.1074/jbc.m110.187583] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The catabolite repressor/activator (Cra) protein is a global sensor and regulator of carbon fluxes through the central metabolic pathways of gram-negative bacteria. To examine the nature of the effector (or effectors) that signal such fluxes to the protein of Pseudomonas putida, the Cra factor of this soil microorganism has been purified and characterized and its three-dimensional structure determined. Analytical ultracentrifugation, gel filtration, and mobility shift assays showed that the effector-free Cra is a dimer that binds an operator DNA sequence in the promoter region of the fruBKA cluster. Furthermore, fructose 1-phosphate (F1P) was found to most efficiently dissociate the Cra-DNA complex. Thermodynamic parameters of the F1P-Cra-DNA interaction calculated by isothermal titration calorimetry revealed that the factor associates tightly to the DNA sequence 5'-TTAAACGTTTCA-3' (K(D) = 26.3 ± 3.1 nM) and that F1P binds the protein with an apparent stoichiometry of 1.06 ± 0.06 molecules per Cra monomer and a K(D) of 209 ± 20 nM. Other possible effectors, like fructose 1,6-bisphosphate, did not display a significant affinity for the regulator under the assay conditions. Moreover, the structure of Cra and its co-crystal with F1P at a 2-Å resolution revealed that F1P fits optimally the geometry of the effector pocket. Our results thus single out F1P as the preferred metabolic effector of the Cra protein of P. putida.
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Affiliation(s)
- Max Chavarría
- Systems Biology Program, Centro Nacional de Biotecnología-Consejo Superior de Investigaciones Científicas, 28049 Cantoblanco-Madrid, Spain
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17
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Zhan H, Sun Z, Matthews KS. Functional impact of polar and acidic substitutions in the lactose repressor hydrophobic monomer.monomer interface with a buried lysine. Biochemistry 2009; 48:1305-14. [PMID: 19166325 DOI: 10.1021/bi801357f] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Despite predicted energetic penalties, the charged K84 side chains of tetrameric lactose repressor protein (LacI) are found buried within the highly hydrophobic monomer.monomer interface that includes side chains of V94 and V96. Once inducer binding has occurred, these K84 side chains move to interact with the more solvent-exposed side chains of D88 and E100'. Previous studies demonstrated that hydrophobic substitutions for K84 increased protein stability and significantly impaired the allosteric response. These results indicated that enhanced hydrophobic interactions at the monomer.monomer interface remove the energetic driving force of the buried charges, decreasing the likelihood of a robust conformational change and stabilizing the structure. We hypothesized that creating a salt bridge network with the lysine side chains by including nearby negatively charged residues might result in a similar outcome. To that end, acidic residues, D and E, and their neutral amides, N and Q, were substituted for the valines at positions 94 and 96. These variants exhibited one or more of the following functional changes: weakened inducer binding, impaired allosteric response, and diminished protein stability. For V96D and V96E, ion pair formation with K84 appears optimal, and the loss of inducer response exceeds that of the hydrophobic K84A and -L variants. However, impacts on functional properties indicate that stabilizing the buried positive charge with polar or ion pair interactions is not functionally equivalent to structural stabilization via hydrophobic enhancement.
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Affiliation(s)
- Hongli Zhan
- Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005, USA.
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18
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Allen LR, Krivov SV, Paci E. Analysis of the free-energy surface of proteins from reversible folding simulations. PLoS Comput Biol 2009; 5:e1000428. [PMID: 19593364 PMCID: PMC2700257 DOI: 10.1371/journal.pcbi.1000428] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2009] [Accepted: 06/01/2009] [Indexed: 11/23/2022] Open
Abstract
Computer generated trajectories can, in principle, reveal the folding pathways of a protein at atomic resolution and possibly suggest general and simple rules for predicting the folded structure of a given sequence. While such reversible folding trajectories can only be determined ab initio using all-atom transferable force-fields for a few small proteins, they can be determined for a large number of proteins using coarse-grained and structure-based force-fields, in which a known folded structure is by construction the absolute energy and free-energy minimum. Here we use a model of the fast folding helical λ-repressor protein to generate trajectories in which native and non-native states are in equilibrium and transitions are accurately sampled. Yet, representation of the free-energy surface, which underlies the thermodynamic and dynamic properties of the protein model, from such a trajectory remains a challenge. Projections over one or a small number of arbitrarily chosen progress variables often hide the most important features of such surfaces. The results unequivocally show that an unprojected representation of the free-energy surface provides important and unbiased information and allows a simple and meaningful description of many-dimensional, heterogeneous trajectories, providing new insight into the possible mechanisms of fast-folding proteins. The process of protein folding is a complex transition from a disordered to an ordered state. Here, we simulate a specific fast-folding protein at the point at which the native and denatured states are at equilibrium and show that obtaining an accurate description of the mechanisms of folding and unfolding is far from trivial. Using simple quantities which quantify the degree of native order is, in the case of this protein, clearly misleading. We show that an unbiased representation of the free-energy surface can be obtained; using such a representation we are able to redesign the landscape and thus modify, upon site-specific “mutations”, the folding and unfolding rates. This leads us to formulate a hypothesis to explain the very fast folding of many proteins.
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Affiliation(s)
- Lucy R. Allen
- School of Physics & Astronomy, University of Leeds, Leeds, United Kingdom
| | - Sergei V. Krivov
- Institute of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
- * E-mail: (SVK); (EP)
| | - Emanuele Paci
- School of Physics & Astronomy, University of Leeds, Leeds, United Kingdom
- Institute of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
- * E-mail: (SVK); (EP)
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19
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Mor A, Ziv G, Levy Y. Simulations of proteins with inhomogeneous degrees of freedom: The effect of thermostats. J Comput Chem 2008; 29:1992-8. [PMID: 18366022 DOI: 10.1002/jcc.20951] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Proteins with a long flexible polymeric tail attached at their N- or C-terminus are studied using molecular dynamics (MD) simulations of a coarse-grained model for protein folding where the temperature is regulated by either the Berendsen or the Langevin thermostat. These thermostats show different abilities to regulate the temperature of these systems that include flexible and more rigid regions. In the simulations with the Berendsen thermostat, the flexible tail is significantly hotter than the protein, both in its folded and unfolded states. Upon weakening the strength of the Berendsen thermostat, the temperature gradient between the fast and the slow degrees of freedom is significantly decreased, yet linkage between the temperatures of the flexible tail and the protein remains. The Langevin thermostat is proven to regulate the temperature of these inhomogenous systems reliably, without discriminating between the slow and fast degrees of freedom. The Langevin thermostat is less sensitive than is the Berendsen thermostat to the strength of the coupling between the protein system and the thermal bath. Our study calls for special care in choosing the thermostat for MD simulations of systems with inhomogenous degrees of freedom. Using the Berendsen thermostat with strong coupling would result in mistaken thermodynamic descriptions of such systems.
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Affiliation(s)
- Amit Mor
- Department of Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel
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20
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Matysiak S, Clementi C. Mapping folding energy landscapes with theory and experiment. Arch Biochem Biophys 2008; 469:29-33. [PMID: 17910943 DOI: 10.1016/j.abb.2007.08.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2007] [Accepted: 08/14/2007] [Indexed: 11/16/2022]
Abstract
The detailed characterization of the overall free energy landscape associated with the folding process of a protein is the ultimate goal in protein folding studies. Modern experimental techniques and all-atom simulations provide a way to obtain accurate thermodynamic and kinetic measurements, but they are oftentimes restricted to probe limited regions of a protein landscape. Although simplified protein models can access larger regions of the landscape, they are built on assumptions and approximations that can affect the accuracy of the results. We review here recent promising approaches that allow to combine the complementary strengths of theory and experiment for a more complete characterization of a protein folding landscape at multiple resolutions. Recent results and possible applications are discussed.
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Affiliation(s)
- Silvina Matysiak
- Department of Chemistry, Rice University, 6100 Main Street, Houston, TX 77005, USA.
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21
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Clementi C. Coarse-grained models of protein folding: toy models or predictive tools? Curr Opin Struct Biol 2007; 18:10-5. [PMID: 18160277 DOI: 10.1016/j.sbi.2007.10.005] [Citation(s) in RCA: 229] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2007] [Accepted: 10/29/2007] [Indexed: 11/16/2022]
Abstract
Coarse-grained models are emerging as a practical alternative to all-atom simulations for the characterization of protein folding mechanisms over long time scales. While a decade ago minimalist toy models were mainly designed to test general hypotheses on the principles regulating protein folding, the latest coarse-grained models are increasingly realistic and can be used to characterize quantitatively the detailed folding mechanism of specific proteins. The ability of such models to reproduce the essential features of folding dynamics suggests that each single atomic degree of freedom is not by itself particularly relevant to folding and supports a statistical mechanical approach to characterize folding transitions. When combined with more refined models and with experimental studies, the systematic investigation of protein systems and complexes using coarse-grained models can advance our theoretical understanding of the actual organizing principles that emerge from the complex network of interactions among protein atomic constituents.
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Affiliation(s)
- Cecilia Clementi
- Department of Chemistry, Rice University, Houston, TX 77005, USA
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22
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Consequences of localized frustration for the folding mechanism of the IM7 protein. Proc Natl Acad Sci U S A 2007; 104:19825-30. [PMID: 18077415 DOI: 10.1073/pnas.0709922104] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In the laboratory, IM7 has been found to have an unusual folding mechanism in which an "on-pathway" intermediate with nonnative interactions is formed. We show that this intermediate is a consequence of an unusual cluster of highly frustrated interactions in the native structure. This cluster is involved in the binding of IM7 to its target, Colicin E7. Redesign of residues in this cluster to eliminate frustration is predicted by simulations to lead to faster folding without the population of an intermediate ensemble.
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23
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Luke K, Perham M, Wittung-Stafshede P. Kinetic Folding and Assembly Mechanisms Differ for Two Homologous Heptamers. J Mol Biol 2006; 363:729-42. [PMID: 16979655 DOI: 10.1016/j.jmb.2006.08.058] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2006] [Revised: 08/15/2006] [Accepted: 08/20/2006] [Indexed: 11/22/2022]
Abstract
Here we investigate the time-resolved folding and assembly mechanism of the heptameric co-chaperonin protein 10 (cpn10) in vitro. The structure of cpn10 is conserved throughout nature: seven beta-barrel subunits are non-covalently assembled through beta-strand pairings in an overall doughnut-like shape. Kinetic folding/assembly experiments of chemically denatured cpn10 from Homo sapiens (hmcpn10) and Aquifex aeolicus (Aacpn10) were monitored by far-UV circular dichroism and fluorescence. We find the processes to be complex, involving several kinetic steps, and to differ between the mesophilic and hyper-thermophilic proteins. The hmcpn10 molecules partition into two parallel pathways, one involving polypeptide folding before protein-protein assembly and another in which inter-protein interactions take place prior to folding. In contrast, the Aacpn10 molecules follow a single sequential path that includes initial monomer misfolding, relaxation to productive intermediates and, subsequently, final folding and heptamer assembly. An A. aeolicus variant lacking the unique C-terminal extension of Aacpn10 displays the same kinetic mechanism as Aacpn10, signifying that the tail is not responsible for the rapid misfolding step. This study demonstrates that molecular details can overrule similarity of native-state topology in defining apparent protein-biophysical properties.
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Affiliation(s)
- Kathryn Luke
- Department of Biochemistry and Cell Biology, Rice University, 6100 Main Street, Houston, TX 77251, USA
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24
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Adib AB. Symmetry relations in chemical kinetics arising from microscopic reversibility. PHYSICAL REVIEW LETTERS 2006; 96:028307. [PMID: 16486660 DOI: 10.1103/physrevlett.96.028307] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2005] [Indexed: 05/06/2023]
Abstract
It is shown that the kinetics of time-reversible chemical reactions having the same equilibrium constant but different initial conditions are closely related to one another by a directly measurable symmetry relation analogous to chemical detailed balance. In contrast to detailed balance, however, this relation does not require knowledge of the elementary steps that underlie the reaction, and remains valid in regimes where the concept of rate constants is ill defined, such as at very short times and in the presence of low activation barriers. Numerical simulations of a model of isomerization in solution are provided to illustrate the symmetry under such conditions, and potential applications in protein folding or unfolding are pointed out.
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Affiliation(s)
- Artur B Adib
- Department of Physics and Department of Chemistry, Box 1843, Brown University, Providence, Rhode Island 02912, USA
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25
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Das P, Wilson CJ, Fossati G, Wittung-Stafshede P, Matthews KS, Clementi C. Characterization of the folding landscape of monomeric lactose repressor: quantitative comparison of theory and experiment. Proc Natl Acad Sci U S A 2005; 102:14569-74. [PMID: 16203982 PMCID: PMC1253569 DOI: 10.1073/pnas.0505844102] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2005] [Indexed: 12/22/2022] Open
Abstract
Recent theoretical/computational studies based on simplified protein models and experimental investigation have suggested that the native structure of a protein plays a primary role in determining the folding rate and mechanism of relatively small single-domain proteins. Here, we extend the study of the relationship between protein topology and folding mechanism to a larger protein with complex topology, by analyzing the folding process of monomeric lactose repressor (MLAc) computationally by using a Gō-like C(alpha) model. Next, we combine simulation and experimental results (see companion article in this issue) to achieve a comprehensive assessment of the folding landscape of this protein. Remarkably, simulated kinetic and equilibrium analyses show an excellent quantitative agreement with the experimental folding data of this study. The results of this comparison show that a simplified, completely unfrustrated C(alpha) model correctly reproduces the complex folding features of a large multidomain protein with complex topology. The success of this effort underlines the importance of synergistic experimental/theoretical approaches to achieve a broader understanding of the folding landscape.
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Affiliation(s)
- Payel Das
- Department of Chemistry, Rice University, Houston, TX 77005, USA
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