101
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Abstract
High-throughput sequencing has enabled many powerful approaches in biological research. Here, we review sequencing approaches to measure frequency changes within engineered mutational libraries subject to selection. These analyses can provide direct estimates of biochemical and fitness effects for all individual mutations across entire genes (and likely compact genomes in the near future) in genetically tractable systems such as microbes, viruses, and mammalian cells. The effects of mutations on experimental fitness can be assessed using sequencing to monitor time-dependent changes in mutant frequency during bulk competitions. The impact of mutations on biochemical functions can be determined using reporters or other means of separating variants based on individual activities (e.g., binding affinity for a partner molecule can be interrogated using surface display of libraries of mutant proteins and isolation of bound and unbound populations). The comprehensive investigation of mutant effects on both biochemical function and experimental fitness provide promising new avenues to investigate the connections between biochemistry, cell physiology, and evolution. We summarize recent findings from systematic mutational analyses; describe how they relate to a field rich in both theory and experimentation; and highlight how they may contribute to ongoing and future research into protein structure-function relationships, systems-level descriptions of cell physiology, and population-genetic inferences on the relative contributions of selection and drift.
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102
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Latysheva NS, Flock T, Weatheritt RJ, Chavali S, Babu MM. How do disordered regions achieve comparable functions to structured domains? Protein Sci 2015; 24:909-22. [PMID: 25752799 PMCID: PMC4456105 DOI: 10.1002/pro.2674] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 02/25/2015] [Accepted: 03/03/2015] [Indexed: 12/19/2022]
Abstract
The traditional structure to function paradigm conceives of a protein's function as emerging from its structure. In recent years, it has been established that unstructured, intrinsically disordered regions (IDRs) in proteins are equally crucial elements for protein function, regulation and homeostasis. In this review, we provide a brief overview of how IDRs can perform similar functions to structured proteins, focusing especially on the formation of protein complexes and assemblies and the mediation of regulated conformational changes. In addition to highlighting instances of such functional equivalence, we explain how differences in the biological and physicochemical properties of IDRs allow them to expand the functional and regulatory repertoire of proteins. We also discuss studies that provide insights into how mutations within functional regions of IDRs can lead to human diseases.
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Affiliation(s)
| | - Tilman Flock
- MRC Laboratory of Molecular BiologyCambridge, CB2 0QH, United Kingdom
| | | | - Sreenivas Chavali
- MRC Laboratory of Molecular BiologyCambridge, CB2 0QH, United Kingdom
| | - M Madan Babu
- MRC Laboratory of Molecular BiologyCambridge, CB2 0QH, United Kingdom
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103
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Toro TB, Nguyen TP, Watt TJ. An improved 96-well turbidity assay for T4 lysozyme activity. MethodsX 2015; 2:256-62. [PMID: 26150996 PMCID: PMC4487725 DOI: 10.1016/j.mex.2015.05.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 05/13/2015] [Indexed: 11/21/2022] Open
Abstract
T4 lysozyme (T4L) is an important model system for investigating the relationship between protein structure and function. Despite being extensively studied, a reliable, quantitative activity assay for T4L has not been developed. Here, we present an improved T4L turbidity assay as well as an affinity-based T4L expression and purification protocol. This assay is designed for 96-well format and utilizes conditions amenable for both T4L and other lysozymes. This protocol enables easy, efficient, and quantitative characterization of T4L variants and allows comparison between different lysozymes. Our method: Is applicable for all lysozymes, with enhanced sensitivity for T4 lysozyme compared to other 96-well plate turbidity assays; Utilizes standardized conditions for comparing T4 lysozyme variants and other lysozymes; and Incorporates a simplified expression and purification protocol for T4 lysozyme.
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Affiliation(s)
- Tasha B Toro
- Department of Chemistry, Xavier University of Louisiana, New Orleans, LA 70125, United States
| | - Thao P Nguyen
- Department of Chemistry, Xavier University of Louisiana, New Orleans, LA 70125, United States
| | - Terry J Watt
- Department of Chemistry, Xavier University of Louisiana, New Orleans, LA 70125, United States
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104
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Abstract
Since determination of the myoglobin structure in 1957, X-ray crystallography, as the anchoring tool of structural biology, has played an instrumental role in deciphering the secrets of life. Knowledge gained through X-ray crystallography has fundamentally advanced our views on cellular processes and greatly facilitated development of modern medicine. In this brief narrative, I describe my personal understanding of the evolution of structural biology through X-ray crystallography-using as examples mechanistic understanding of protein kinases and integral membrane proteins-and comment on the impact of technological development and outlook of X-ray crystallography.
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Affiliation(s)
- Yigong Shi
- Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China.
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105
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Lamazares E, Clemente I, Bueno M, Velázquez-Campoy A, Sancho J. Rational stabilization of complex proteins: a divide and combine approach. Sci Rep 2015; 5:9129. [PMID: 25774740 PMCID: PMC4360737 DOI: 10.1038/srep09129] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 02/19/2015] [Indexed: 11/09/2022] Open
Abstract
Increasing the thermostability of proteins is often crucial for their successful use as analytic, synthetic or therapeutic tools. Most rational thermostabilization strategies were developed on small two-state proteins and, unsurprisingly, they tend to fail when applied to the much more abundant, larger, non-fully cooperative proteins. We show that the key to stabilize the latter is to know the regions of lower stability. To prove it, we have engineered apoflavodoxin, a non-fully cooperative protein on which previous thermostabilizing attempts had failed. We use a step-wise combination of structure-based, rationally-designed, stabilizing mutations confined to the less stable structural region, and obtain variants that, according to their van't Hoff to calorimetric enthalpy ratios, exhibit fully-cooperative thermal unfolding with a melting temperature of 75°C, 32 degrees above the lower melting temperature of the non-cooperative wild type protein. The ideas introduced here may also be useful for the thermostabilization of complex proteins through formulation or using specific stabilizing ligands (e.g. pharmacological chaperones).
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Affiliation(s)
- Emilio Lamazares
- 1] Biocomputation and Complex Systems Physics Institute (BIFI)-Joint Unit BIFI-IQFR (CSIC), Universidad de Zaragoza, Zaragoza, Spain [2] Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, Zaragoza, Spain
| | - Isabel Clemente
- 1] Biocomputation and Complex Systems Physics Institute (BIFI)-Joint Unit BIFI-IQFR (CSIC), Universidad de Zaragoza, Zaragoza, Spain [2] Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, Zaragoza, Spain
| | - Marta Bueno
- 1] Biocomputation and Complex Systems Physics Institute (BIFI)-Joint Unit BIFI-IQFR (CSIC), Universidad de Zaragoza, Zaragoza, Spain [2] Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, Zaragoza, Spain
| | - Adrián Velázquez-Campoy
- 1] Biocomputation and Complex Systems Physics Institute (BIFI)-Joint Unit BIFI-IQFR (CSIC), Universidad de Zaragoza, Zaragoza, Spain [2] Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, Zaragoza, Spain [3] Fundación ARAID, Gobierno de Aragón, Spain
| | - Javier Sancho
- 1] Biocomputation and Complex Systems Physics Institute (BIFI)-Joint Unit BIFI-IQFR (CSIC), Universidad de Zaragoza, Zaragoza, Spain [2] Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, Zaragoza, Spain
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106
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Verdurmen WPR, Luginbühl M, Honegger A, Plückthun A. Efficient cell-specific uptake of binding proteins into the cytoplasm through engineered modular transport systems. J Control Release 2015; 200:13-22. [PMID: 25526701 DOI: 10.1016/j.jconrel.2014.12.019] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2014] [Revised: 12/13/2014] [Accepted: 12/16/2014] [Indexed: 12/15/2022]
Abstract
Through advances in protein scaffold engineering and selection technologies, highly specific binding proteins, which fold under reducing conditions, can be generated against virtually all targets. Despite tremendous therapeutic opportunities, intracellular applications are hindered by difficulties associated with achieving cytosolic delivery, compounded by even correctly measuring it. Here, we addressed cytosolic delivery systematically through the development of a biotin ligase-based assay that objectively quantifies cytosolic delivery in a generic fashion. We developed modular transport systems that consist of a designed ankyrin repeat protein (DARPin) for receptor targeting and a different DARPin for intracellular recognition and a bacterial toxin-derived component for cytosolic translocation. We show that both anthrax pores and the translocation domain of Pseudomonas exotoxin A (ETA) efficiently deliver DARPins into the cytosol. We found that the cargo must not exceed a threshold thermodynamic stability for anthrax pores, which can be addressed by engineering, while the ETA pathway does not appear to have this restriction.
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Affiliation(s)
- Wouter P R Verdurmen
- Dept of Biochemistry, University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland.
| | - Manuel Luginbühl
- Dept of Biochemistry, University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland.
| | - Annemarie Honegger
- Dept of Biochemistry, University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland.
| | - Andreas Plückthun
- Dept of Biochemistry, University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland.
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107
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Samish I, Bourne PE, Najmanovich RJ. Achievements and challenges in structural bioinformatics and computational biophysics. Bioinformatics 2014; 31:146-50. [PMID: 25488929 PMCID: PMC4271151 DOI: 10.1093/bioinformatics/btu769] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Motivation: The field of structural bioinformatics and computational biophysics has undergone a revolution in the last 10 years. Developments that are captured annually through the 3DSIG meeting, upon which this article reflects. Results: An increase in the accessible data, computational resources and methodology has resulted in an increase in the size and resolution of studied systems and the complexity of the questions amenable to research. Concomitantly, the parameterization and efficiency of the methods have markedly improved along with their cross-validation with other computational and experimental results. Conclusion: The field exhibits an ever-increasing integration with biochemistry, biophysics and other disciplines. In this article, we discuss recent achievements along with current challenges within the field. Contact:Rafael.Najmanovich@USherbrooke.ca
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Affiliation(s)
- Ilan Samish
- Department of Plant Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel, Ort Braude College, Karmiel, 2161002, Israel, Office of the Director, National Institutes of Health, Bethesda, MD 20814, USA and Department of Biochemistry, University of Sherbrooke, Sherbrooke, J1H 5N4, Canada Department of Plant Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel, Ort Braude College, Karmiel, 2161002, Israel, Office of the Director, National Institutes of Health, Bethesda, MD 20814, USA and Department of Biochemistry, University of Sherbrooke, Sherbrooke, J1H 5N4, Canada
| | - Philip E Bourne
- Department of Plant Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel, Ort Braude College, Karmiel, 2161002, Israel, Office of the Director, National Institutes of Health, Bethesda, MD 20814, USA and Department of Biochemistry, University of Sherbrooke, Sherbrooke, J1H 5N4, Canada
| | - Rafael J Najmanovich
- Department of Plant Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel, Ort Braude College, Karmiel, 2161002, Israel, Office of the Director, National Institutes of Health, Bethesda, MD 20814, USA and Department of Biochemistry, University of Sherbrooke, Sherbrooke, J1H 5N4, Canada
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108
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Modified T4 Lysozyme Fusion Proteins Facilitate G Protein-Coupled Receptor Crystallogenesis. Structure 2014; 22:1657-64. [PMID: 25450769 DOI: 10.1016/j.str.2014.08.022] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 08/11/2014] [Accepted: 08/13/2014] [Indexed: 12/11/2022]
Abstract
G protein-coupled receptors (GPCRs) mediate the majority of cellular responses to hormones and neurotransmitters. Most GPCR crystal structures have been obtained using a fusion protein strategy where the flexible third intracellular loop is replaced by T4 lysozyme (T4L). However, wild-type T4L may not be ideally suited for all GPCRs because of its size and the inherent flexibility between the N- and C-terminal subdomains. Here we report two modified T4L variants, designed to address flexibility and size, that can be used to optimize crystal quality or promote alternative packing interactions. These variants were tested on the M3 muscarinic receptor (M3). The original M3-T4L fusion protein produced twinned crystals that yielded a 3.4 Å structure from a 70 crystal data set. We replaced T4L with the modified T4L variants. Both T4L variants yielded M3 muscarinic receptor crystals with alternate lattices that were not twinned, including one that was solved at 2.8 Å resolution.
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109
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Biophysical highlights from 54 years of macromolecular crystallography. Biophys J 2014; 106:510-25. [PMID: 24507592 DOI: 10.1016/j.bpj.2014.01.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2013] [Accepted: 01/03/2014] [Indexed: 12/22/2022] Open
Abstract
The United Nations has declared 2014 the International Year of Crystallography, and in commemoration, this review features a selection of 54 notable macromolecular crystal structures that have illuminated the field of biophysics in the 54 years since the first excitement of the myoglobin and hemoglobin structures in 1960. Chronological by publication of the earliest solved structure, each illustrated entry briefly describes key concepts or methods new at the time and key later work leveraged by knowledge of the three-dimensional atomic structure.
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110
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Role of cavities and hydration in the pressure unfolding of T4 lysozyme. Proc Natl Acad Sci U S A 2014; 111:13846-51. [PMID: 25201963 DOI: 10.1073/pnas.1410655111] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
It is well known that high hydrostatic pressures can induce the unfolding of proteins. The physical underpinnings of this phenomenon have been investigated extensively but remain controversial. Changes in solvation energetics have been commonly proposed as a driving force for pressure-induced unfolding. Recently, the elimination of void volumes in the native folded state has been argued to be the principal determinant. Here we use the cavity-containing L99A mutant of T4 lysozyme to examine the pressure-induced destabilization of this multidomain protein by using solution NMR spectroscopy. The cavity-containing C-terminal domain completely unfolds at moderate pressures, whereas the N-terminal domain remains largely structured to pressures as high as 2.5 kbar. The sensitivity to pressure is suppressed by the binding of benzene to the hydrophobic cavity. These results contrast to the pseudo-WT protein, which has a residual cavity volume very similar to that of the L99A-benzene complex but shows extensive subglobal reorganizations with pressure. Encapsulation of the L99A mutant in the aqueous nanoscale core of a reverse micelle is used to examine the hydration of the hydrophobic cavity. The confined space effect of encapsulation suppresses the pressure-induced unfolding transition and allows observation of the filling of the cavity with water at elevated pressures. This indicates that hydration of the hydrophobic cavity is more energetically unfavorable than global unfolding. Overall, these observations point to a range of cooperativity and energetics within the T4 lysozyme molecule and illuminate the fact that small changes in physical parameters can significantly alter the pressure sensitivity of proteins.
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111
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Hausrath AC. Model for coupled insertion and folding of membrane-spanning proteins. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:022707. [PMID: 25215758 DOI: 10.1103/physreve.90.022707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Indexed: 06/03/2023]
Abstract
Current understanding of the forces directing the folding of integral membrane proteins is very limited compared to the detailed picture available for water-soluble proteins. While mechanistic studies of the folding process in vitro have been conducted for only a small number of membrane proteins, the available evidence indicates that their folding process is thermodynamically driven like that of soluble proteins. In vivo, however, the majority of integral membrane proteins are installed in membranes by dedicated machinery, suggesting that the cellular systems may act to facilitate and regulate the spontaneous physical process of folding. Both the in vitro folding process and the in vivo pathway must navigate an energy landscape dominated by the energetically favorable burial of hydrophobic segments in the membrane interior and the opposition to folding due to the need for passage of polar segments across the membrane. This manuscript describes a simple, exactly solvable model which incorporates these essential features of membrane protein folding. The model is used to compare the folding time under conditions which depict both the in vitro and in vivo pathways. It is proposed that the cellular complexes responsible for insertion of membrane proteins act by lowering the energy barrier for passage of polar regions through the membrane, thereby allowing the chain to more rapidly achieve the folded state.
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Affiliation(s)
- Andrew C Hausrath
- Department of Chemistry and Biochemistry and Program in Applied Mathematics, University of Arizona, Tucson, Arizona 85721, USA
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112
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Luft JR, Newman J, Snell EH. Crystallization screening: the influence of history on current practice. Acta Crystallogr F Struct Biol Commun 2014; 70:835-53. [PMID: 25005076 PMCID: PMC4089519 DOI: 10.1107/s2053230x1401262x] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Accepted: 05/30/2014] [Indexed: 11/17/2022] Open
Abstract
While crystallization historically predates crystallography, it is a critical step for the crystallographic process. The rich history of crystallization and how that history influences current practices is described. The tremendous impact of crystallization screens on the field is discussed.
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Affiliation(s)
- Joseph R. Luft
- Hauptman–Woodward Medical Research Institute, 700 Ellicott Street, Buffalo, NY 14203, USA
| | - Janet Newman
- CSIRO Collaborative Crystallisation Centre, 343 Royal Parade, Parkville, VIC 3052, Australia
| | - Edward H. Snell
- Hauptman–Woodward Medical Research Institute, 700 Ellicott Street, Buffalo, NY 14203, USA
- Department of Structural Biology, SUNY Buffalo, 700 Ellicott Street, Buffalo, NY 14203, USA
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113
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Dudek MJ. A detailed representation of electrostatic energy in prediction of sequence and pH dependence of protein stability. Proteins 2014; 82:2497-511. [DOI: 10.1002/prot.24613] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Revised: 05/11/2014] [Accepted: 05/15/2014] [Indexed: 11/05/2022]
Affiliation(s)
- Michael J. Dudek
- Protabit LLC; 250 S Oak Knoll Ave. #211 Pasadena California 91101
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114
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Nick Pace C, Scholtz JM, Grimsley GR. Forces stabilizing proteins. FEBS Lett 2014; 588:2177-84. [PMID: 24846139 DOI: 10.1016/j.febslet.2014.05.006] [Citation(s) in RCA: 236] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Revised: 04/30/2014] [Accepted: 05/05/2014] [Indexed: 11/30/2022]
Abstract
The goal of this article is to summarize what has been learned about the major forces stabilizing proteins since the late 1980s when site-directed mutagenesis became possible. The following conclusions are derived from experimental studies of hydrophobic and hydrogen bonding variants. (1) Based on studies of 138 hydrophobic interaction variants in 11 proteins, burying a -CH2- group on folding contributes 1.1±0.5 kcal/mol to protein stability. (2) The burial of non-polar side chains contributes to protein stability in two ways: first, a term that depends on the removal of the side chains from water and, more importantly, the enhanced London dispersion forces that result from the tight packing in the protein interior. (3) Based on studies of 151 hydrogen bonding variants in 15 proteins, forming a hydrogen bond on folding contributes 1.1±0.8 kcal/mol to protein stability. (4) The contribution of hydrogen bonds to protein stability is strongly context dependent. (5) Hydrogen bonds by side chains and peptide groups make similar contributions to protein stability. (6) Polar group burial can make a favorable contribution to protein stability even if the polar group is not hydrogen bonded. (7) Hydrophobic interactions and hydrogen bonds both make large contributions to protein stability.
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Affiliation(s)
- C Nick Pace
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, United States; Department of Molecular and Cellular Medicine, Texas A&M University Health Science Center, College Station, TX 77843, United States.
| | - J Martin Scholtz
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, United States; Department of Molecular and Cellular Medicine, Texas A&M University Health Science Center, College Station, TX 77843, United States
| | - Gerald R Grimsley
- Department of Molecular and Cellular Medicine, Texas A&M University Health Science Center, College Station, TX 77843, United States
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115
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Schoene C, Fierer JO, Bennett SP, Howarth M. SpyTag/SpyCatcher Cyclization Confers Resilience to Boiling on a Mesophilic Enzyme. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201402519] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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116
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Schoene C, Fierer JO, Bennett SP, Howarth M. SpyTag/SpyCatcher cyclization confers resilience to boiling on a mesophilic enzyme. Angew Chem Int Ed Engl 2014; 53:6101-4. [PMID: 24817566 DOI: 10.1002/anie.201402519] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Indexed: 11/09/2022]
Abstract
SpyTag is a peptide that spontaneously forms an amide bond with its protein partner SpyCatcher. SpyTag was fused at the N terminus of β-lactamase and SpyCatcher at the C terminus so that the partners could react to lock together the termini of the enzyme. The wild-type enzyme aggregates above 37 °C, with irreversible loss of activity. Cyclized β-lactamase was soluble even after heating at 100 °C; after cooling, the catalytic activity was restored. SpyTag/SpyCatcher cyclization led to a much larger increase in stability than that achieved through point mutation or alternative approaches to cyclization. Cyclized dihydrofolate reductase was similarly resilient. Analyzing unfolding through calorimetry indicated that cyclization did not increase the unfolding temperature but rather facilitated refolding after thermal stress. SpyTag/SpyCatcher sandwiching represents a simple and efficient route to enzyme cyclization, with potential to greatly enhance the robustness of biocatalysts.
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Affiliation(s)
- Christopher Schoene
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU (UK)
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117
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Yahashiri A, Rubach JK, Plapp BV. Effects of cavities at the nicotinamide binding site of liver alcohol dehydrogenase on structure, dynamics and catalysis. Biochemistry 2014; 53:881-94. [PMID: 24437493 PMCID: PMC3969020 DOI: 10.1021/bi401583f] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
![]()
A role
for protein dynamics in enzymatic catalysis of hydrogen
transfer has received substantial scientific support, but the connections
between protein structure and catalysis remain to be established.
Valine residues 203 and 207 are at the binding site for the nicotinamide
ring of the coenzyme in liver alcohol dehydrogenase and have been
suggested to facilitate catalysis with “protein-promoting vibrations”
(PPV). We find that the V207A substitution has small effects on steady-state
kinetic constants and the rate of hydrogen transfer; the introduced
cavity is empty and is tolerated with minimal effects on structure
(determined at 1.2 Å for the complex with NAD+ and
2,3,4,5,6-pentafluorobenzyl alcohol). Thus, no evidence is found to
support a role for Val-207 in the dynamics of catalysis. The protein
structures and ligand geometries (including donor–acceptor
distances) in the V203A enzyme complexed with NAD+ and
2,3,4,5,6-pentafluorobenzyl alcohol or 2,2,2-trifluoroethanol (determined
at 1.1 Å) are very similar to those for the wild-type enzyme,
except that the introduced cavity accommodates a new water molecule
that contacts the nicotinamide ring. The structures of the V203A enzyme
complexes suggest, in contrast to previous studies, that the diminished
tunneling and decreased rate of hydride transfer (16-fold, relative
to that of the wild-type enzyme) are not due to differences in ground-state
ligand geometries. The V203A substitution may alter the PPV and the
reorganization energy for hydrogen transfer, but the protein scaffold
and equilibrium thermal motions within the Michaelis complex may be
more significant for enzyme catalysis.
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Affiliation(s)
- Atsushi Yahashiri
- Department of Biochemistry, The University of Iowa , Iowa City, Iowa 52242-1109, United States
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118
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Konishi A, Ma X, Yasukawa K. Stabilization of Moloney murine leukemia virus reverse transcriptase by site-directed mutagenesis of surface residue Val433. Biosci Biotechnol Biochem 2014; 78:75-8. [DOI: 10.1080/09168451.2014.877186] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Abstract
After thermal incubation at 48 °C for 10 min, single variants of Moloney murine leukemia virus reverse transcriptase, V433R and V433K in which a surface hydrophobic residue, Val433, was mutated, retained 55% of initial reverse transcription activity, while the wild-type enzyme retained 17%. After thermal incubation at 50 °C for 10 min, multiple variants D108R/E286R/V433R and D108R/E286R/V433R/D524A, in which Val433→Arg was combined with stabilizing mutations we identified previously, Asp108→Arg and Glu286→Arg, and RNase H activity-eliminating mutation Asp524→Ala, retained 70% of initial activity, exhibiting higher stability than V433R or V433K.
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Affiliation(s)
- Atsushi Konishi
- Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Xiaochen Ma
- Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Kiyoshi Yasukawa
- Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
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119
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Dombkowski AA, Sultana KZ, Craig DB. Protein disulfide engineering. FEBS Lett 2013; 588:206-12. [PMID: 24291258 DOI: 10.1016/j.febslet.2013.11.024] [Citation(s) in RCA: 174] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 11/15/2013] [Accepted: 11/18/2013] [Indexed: 11/29/2022]
Abstract
Improving the stability of proteins is an important goal in many biomedical and industrial applications. A logical approach is to emulate stabilizing molecular interactions found in nature. Disulfide bonds are covalent interactions that provide substantial stability to many proteins and conform to well-defined geometric conformations, thus making them appealing candidates in protein engineering efforts. Disulfide engineering is the directed design of novel disulfide bonds into target proteins. This important biotechnological tool has achieved considerable success in a wide range of applications, yet the rules that govern the stabilizing effects of disulfide bonds are not fully characterized. Contrary to expectations, many designed disulfide bonds have resulted in decreased stability of the modified protein. We review progress in disulfide engineering, with an emphasis on the issue of stability and computational methods that facilitate engineering efforts.
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Affiliation(s)
- Alan A Dombkowski
- Carman and Ann Adams Department of Pediatrics, Wayne State University School of Medicine, Detroit, MI 48201, USA.
| | - Kazi Zakia Sultana
- Department of Computer Science & Engineering, Chittagong University of Engineering & Technology, Chittagong 4349, Bangladesh
| | - Douglas B Craig
- Carman and Ann Adams Department of Pediatrics, Wayne State University School of Medicine, Detroit, MI 48201, USA
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120
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Schwans JP, Sunden F, Gonzalez A, Tsai Y, Herschlag D. Uncovering the determinants of a highly perturbed tyrosine pKa in the active site of ketosteroid isomerase. Biochemistry 2013; 52:7840-55. [PMID: 24151972 PMCID: PMC3890242 DOI: 10.1021/bi401083b] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Within the idiosyncratic enzyme active-site environment, side chain and ligand pKa values can be profoundly perturbed relative to their values in aqueous solution. Whereas structural inspection of systems has often attributed perturbed pKa values to dominant contributions from placement near charged groups or within hydrophobic pockets, Tyr57 of a Pseudomonas putida ketosteroid isomerase (KSI) mutant, suggested to have a pKa perturbed by nearly 4 units to 6.3, is situated within a solvent-exposed active site devoid of cationic side chains, metal ions, or cofactors. Extensive comparisons among 45 variants with mutations in and around the KSI active site, along with protein semisynthesis, (13)C NMR spectroscopy, absorbance spectroscopy, and X-ray crystallography, was used to unravel the basis for this perturbed Tyr pKa. The results suggest that the origin of large energetic perturbations are more complex than suggested by visual inspection. For example, the introduction of positively charged residues near Tyr57 raises its pKa rather than lowers it; this effect, and part of the increase in the Tyr pKa from the introduction of nearby anionic groups, arises from accompanying active-site structural rearrangements. Other mutations with large effects also cause structural perturbations or appear to displace a structured water molecule that is part of a stabilizing hydrogen-bond network. Our results lead to a model in which three hydrogen bonds are donated to the stabilized ionized Tyr, with these hydrogen-bond donors, two Tyr side chains, and a water molecule positioned by other side chains and by a water-mediated hydrogen-bond network. These results support the notion that large energetic effects are often the consequence of multiple stabilizing interactions rather than a single dominant interaction. Most generally, this work provides a case study for how extensive and comprehensive comparisons via site-directed mutagenesis in a tight feedback loop with structural analysis can greatly facilitate our understanding of enzyme active-site energetics. The extensive data set provided may also be a valuable resource for those wishing to extensively test computational approaches for determining enzymatic pKa values and energetic effects.
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Affiliation(s)
- Jason P. Schwans
- Department of Biochemistry, Stanford University, Stanford, California 94305
| | - Fanny Sunden
- Department of Biochemistry, Stanford University, Stanford, California 94305
| | - Ana Gonzalez
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025
| | - Yingssu Tsai
- Department of Chemistry, Stanford University, Stanford, California 94305
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025
| | - Daniel Herschlag
- Department of Biochemistry, Stanford University, Stanford, California 94305
- Department of Chemistry, Stanford University, Stanford, California 94305
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121
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Conformational selection and adaptation to ligand binding in T4 lysozyme cavity mutants. Proc Natl Acad Sci U S A 2013; 110:E4306-15. [PMID: 24167295 DOI: 10.1073/pnas.1318754110] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The studies presented here explore the relationship between protein packing and molecular flexibility using ligand-binding cavity mutants of T4 lysozyme. Although previously reported crystal structures of the mutants investigated show single conformations that are similar to the WT protein, site-directed spin labeling in solution reveals additional conformational substates in equilibrium exchange with a WT-like population. Remarkably, binding of ligands, including the general anesthetic halothane shifts the population to the WT-like state, consistent with a conformational selection model of ligand binding, but structural adaptation to the ligand is also apparent in one mutant. Distance mapping with double electron-electron resonance spectroscopy and the absence of ligand binding suggest that the new substates induced by the cavity-creating mutations represent alternate packing modes in which the protein fills or partially fills the cavity with side chains, including the spin label in one case; external ligands compete with the side chains for the cavity space, stabilizing the WT conformation. The results have implications for mechanisms of anesthesia, the response of proteins to hydrostatic pressure, and protein engineering.
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122
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Radou G, Enciso M, Krivov S, Paci E. Modulation of a protein free-energy landscape by circular permutation. J Phys Chem B 2013; 117:13743-7. [PMID: 24090448 PMCID: PMC3821731 DOI: 10.1021/jp406818t] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
![]()
Circular
permutations usually retain the native structure and function
of a protein while inevitably perturbing its folding dynamics. By
using simulations with a structure-based model and a rigorous methodology
to determine free-energy surfaces from trajectories, we evaluate the
effect of a circular permutation on the free-energy landscape of the
protein T4 lysozyme. We observe changes which, although subtle, largely
affect the cooperativity between the two subdomains. Such a change
in cooperativity has been previously experimentally observed and recently
also characterized using single molecule optical tweezers and the
Crooks relation. The free-energy landscapes show that both the wild
type and circular permutant have an on-pathway intermediate, previously
experimentally characterized, in which one of the subdomains is completely
formed. The landscapes, however, differ in the position of the rate-limiting
step for folding, which occurs before the intermediate in the wild
type and after in the circular permutant. This shift of transition
state explains the observed change in the cooperativity. The underlying
free-energy landscape thus provides a microscopic description of the
folding dynamics and the connection between circular permutation and
the loss of cooperativity experimentally observed.
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Affiliation(s)
- Gaël Radou
- Astbury Centre for Structural Molecular Biology, University of Leeds , Leeds LS2 9JT, United Kingdom
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123
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Abstract
Single molecule bioelectronic circuits provide an opportunity to study chemical kinetics and kinetic variability with bond-by-bond resolution. To demonstrate this approach, we examined the catalytic activity of T4 lysozyme processing peptidoglycan substrates. Monitoring a single lysozyme molecule through changes in a circuit's conductance helped elucidate unexplored and previously invisible aspects of lysozyme's catalytic mechanism and demonstrated lysozyme to be a processive enzyme governed by 9 independent time constants. The variation of each time constant with pH or substrate crosslinking provided different insights into catalytic activity and dynamic disorder. Overall, ten lysozyme variants were synthesized and tested in single molecule circuits to dissect the transduction of chemical activity into electronic signals. Measurements show that a single amino acid with the appropriate properties is sufficient for good signal generation, proving that the single molecule circuit technique can be easily extended to other proteins.
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Affiliation(s)
- Yongki Choi
- Department of Physics and Astronomy, University of California at Irvine, Irvine, California 92697, United States
| | - Gregory A. Weiss
- Departments of Chemistry and Molecular Biology and Biochemistry, University of California at Irvine, Irvine, California 92697, United States
| | - Philip G. Collins
- Department of Physics and Astronomy, University of California at Irvine, Irvine, California 92697, United States
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124
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Riera C, Lois S, de la Cruz X. Prediction of pathological mutations in proteins: the challenge of integrating sequence conservation and structure stability principles. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2013. [DOI: 10.1002/wcms.1170] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Casandra Riera
- Laboratory of Translational Bioinformatics in Neuroscience; VHIR; Barcelona Spain
| | - Sergio Lois
- Laboratory of Translational Bioinformatics in Neuroscience; VHIR; Barcelona Spain
| | - Xavier de la Cruz
- Laboratory of Translational Bioinformatics in Neuroscience; VHIR; Barcelona Spain
- Institució Catalana per la Recerca i Estudis Avançats (ICREA); Barcelona Spain
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125
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Affiliation(s)
- Robert O J Weinzierl
- Department of Life Sciences, Division of Biomolecular Sciences, Imperial College London , Sir Alexander Fleming Building, Exhibition Road, London SW7 2AZ, United Kingdom
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126
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Jin M, Ye T, Zhang X. Roles of bacteriophage GVE2 endolysin in host lysis at high temperatures. Microbiology (Reading) 2013; 159:1597-1605. [DOI: 10.1099/mic.0.067611-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Affiliation(s)
- Min Jin
- Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education and College of Life Sciences, Zhejiang University, Hangzhou 310058, PR China
| | - Ting Ye
- Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education and College of Life Sciences, Zhejiang University, Hangzhou 310058, PR China
| | - Xiaobo Zhang
- Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education and College of Life Sciences, Zhejiang University, Hangzhou 310058, PR China
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127
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Czabotar PE, Westphal D, Dewson G, Ma S, Hockings C, Fairlie WD, Lee EF, Yao S, Robin AY, Smith BJ, Huang DCS, Kluck RM, Adams JM, Colman PM. Bax crystal structures reveal how BH3 domains activate Bax and nucleate its oligomerization to induce apoptosis. Cell 2013; 152:519-31. [PMID: 23374347 DOI: 10.1016/j.cell.2012.12.031] [Citation(s) in RCA: 432] [Impact Index Per Article: 39.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Revised: 10/11/2012] [Accepted: 12/10/2012] [Indexed: 02/06/2023]
Abstract
In stressed cells, apoptosis ensues when Bcl-2 family members Bax or Bak oligomerize and permeabilize the mitochondrial outer membrane. Certain BH3-only relatives can directly activate them to mediate this pivotal, poorly understood step. To clarify the conformational changes that induce Bax oligomerization, we determined crystal structures of BaxΔC21 treated with detergents and BH3 peptides. The peptides bound the Bax canonical surface groove but, unlike their complexes with prosurvival relatives, dissociated Bax into two domains. The structures define the sequence signature of activator BH3 domains and reveal how they can activate Bax via its groove by favoring release of its BH3 domain. Furthermore, Bax helices α2-α5 alone adopted a symmetric homodimer structure, supporting the proposal that two Bax molecules insert their BH3 domain into each other's surface groove to nucleate oligomerization. A planar lipophilic surface on this homodimer may engage the membrane. Our results thus define critical Bax transitions toward apoptosis.
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Affiliation(s)
- Peter E Czabotar
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria 3052, Australia.
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128
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Merski M, Shoichet BK. The impact of introducing a histidine into an apolar cavity site on docking and ligand recognition. J Med Chem 2013; 56:2874-84. [PMID: 23473072 PMCID: PMC3624796 DOI: 10.1021/jm301823g] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
![]()
Simplified
model binding sites allow one to isolate entangled terms
in molecular energy functions. Here, we investigate the effects on
ligand recognition of the introduction of a histidine into a hydrophobic
cavity in lysozyme. We docked 656040 molecules and tested 26 highly
and nine poorly ranked. Twenty-one highly ranked molecules bound and
five were false positives, while three poorly ranked molecules were
false negatives. In the 16 X-ray complexes now known, the docking
predictions overlaid well with the crystallographic results. Although
ligand enrichment was high, the false negatives, the false positives,
and the inability to rank order illuminated weaknesses in our scoring,
particularly overweighed apolar and underweighted polar terms. Adjusting
these led to new problems, reflecting the entangled nature of docking
scoring functions. Changes in ligand affinity relative to other lysozyme
cavities speak to the subtleties of molecular recognition even in
these simple sites and to their relevance for testing different models
of recognition.
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Affiliation(s)
- Matthew Merski
- Department of Pharmaceutical Chemistry, University of California San Francisco, 1700 Fourth Street, San Francisco, California 94158-2550, United States
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129
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Rational design of a fibroblast growth factor 21-based clinical candidate, LY2405319. PLoS One 2013; 8:e58575. [PMID: 23536797 PMCID: PMC3594191 DOI: 10.1371/journal.pone.0058575] [Citation(s) in RCA: 138] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2012] [Accepted: 02/05/2013] [Indexed: 01/08/2023] Open
Abstract
Fibroblast growth factor 21 is a novel hormonal regulator with the potential to treat a broad variety of metabolic abnormalities, such as type 2 diabetes, obesity, hepatic steatosis, and cardiovascular disease. Human recombinant wild type FGF21 (FGF21) has been shown to ameliorate metabolic disorders in rodents and non-human primates. However, development of FGF21 as a drug is challenging and requires re-engineering of its amino acid sequence to improve protein expression and formulation stability. Here we report the design and characterization of a novel FGF21 variant, LY2405319. To enable the development of a potential drug product with a once-daily dosing profile, in a preserved, multi-use formulation, an additional disulfide bond was introduced in FGF21 through Leu118Cys and Ala134Cys mutations. FGF21 was further optimized by deleting the four N-terminal amino acids, His-Pro-Ile-Pro (HPIP), which was subject to proteolytic cleavage. In addition, to eliminate an O-linked glycosylation site in yeast a Ser167Ala mutation was introduced, thus allowing large-scale, homogenous protein production in Pichia pastoris. Altogether re-engineering of FGF21 led to significant improvements in its biopharmaceutical properties. The impact of these changes was assessed in a panel of in vitro and in vivo assays, which confirmed that biological properties of LY2405319 were essentially identical to FGF21. Specifically, subcutaneous administration of LY2405319 in ob/ob and diet-induced obese (DIO) mice over 7–14 days resulted in a 25–50% lowering of plasma glucose coupled with a 10–30% reduction in body weight. Thus, LY2405319 exhibited all the biopharmaceutical and biological properties required for initiation of a clinical program designed to test the hypothesis that administration of exogenous FGF21 would result in effects on disease-related metabolic parameters in humans.
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130
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Knaff DB, Sutton RB. Utility of Synechocystis sp. PCC 6803 glutaredoxin A as a platform to study high-resolution mutagenesis of proteins. FRONTIERS IN PLANT SCIENCE 2013; 4:461. [PMID: 24298277 PMCID: PMC3828617 DOI: 10.3389/fpls.2013.00461] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Accepted: 10/26/2013] [Indexed: 05/10/2023]
Abstract
Glutaredoxin from the cyanobacterium Synechocystis sp. PCC 6803 is a small protein, containing only 88 amino acids, that participates in a large number of redox reactions, serving both as an electron donor for enzyme-catalyzed reductions and as a regulator of diverse metabolic pathways. The crystal structures of glutaredoxins from several species have been solved, including the glutaredoxin A isoform from the cyanobacterium Synechocystis sp. PCC 6803. We have utilized the small size of Synechocystis glutaredoxin A and its propensity to form protein crystals that diffract to high resolution to explore a long-standing question in biochemistry; i.e., what are the effects of mutations on protein structure and function? Taking advantage of these properties, we have initiated a long-term educational project that would examine the structural and biochemical changes in glutaredoxin as a function of single-point mutational replacements. Here, we report some of the mutational effects that we have observed to date.
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Affiliation(s)
- David B. Knaff
- Department of Chemistry and Biochemistry, Texas Tech UniversityLubbock, TX, USA
- Center for Biotechnology and Genomics, Texas Tech UniversityLubbock, TX, USA
| | - Roger B. Sutton
- Department of Cell Physiology and Molecular Biophysics, Texas Tech University Health Sciences CenterLubbock, TX, USA
- Center for Membrane Protein Research, Texas Tech University Health Sciences CenterLubbock, TX, USA
- *Correspondence: Roger B. Sutton, Department of Cell Physiology and Molecular Biophysics, Texas Tech University Health Sciences Center, 3601 4th St., Mailstop 6551, Lubbock, TX 79430-6551, USA e-mail:
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131
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Dessau M, Goldhill D, McBride RL, Turner PE, Modis Y. Selective pressure causes an RNA virus to trade reproductive fitness for increased structural and thermal stability of a viral enzyme. PLoS Genet 2012; 8:e1003102. [PMID: 23209446 PMCID: PMC3510033 DOI: 10.1371/journal.pgen.1003102] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 10/03/2012] [Indexed: 11/18/2022] Open
Abstract
The modulation of fitness by single mutational substitutions during environmental change is the most fundamental consequence of natural selection. The antagonistic tradeoffs of pleiotropic mutations that can be selected under changing environments therefore lie at the foundation of evolutionary biology. However, the molecular basis of fitness tradeoffs is rarely determined in terms of how these pleiotropic mutations affect protein structure. Here we use an interdisciplinary approach to study how antagonistic pleiotropy and protein function dictate a fitness tradeoff. We challenged populations of an RNA virus, bacteriophage Φ6, to evolve in a novel temperature environment where heat shock imposed extreme virus mortality. A single amino acid substitution in the viral lysin protein P5 (V207F) favored improved stability, and hence survival of challenged viruses, despite a concomitant tradeoff that decreased viral reproduction. This mutation increased the thermostability of P5. Crystal structures of wild-type, mutant, and ligand-bound P5 reveal the molecular basis of this thermostabilization--the Phe207 side chain fills a hydrophobic cavity that is unoccupied in the wild-type--and identify P5 as a lytic transglycosylase. The mutation did not reduce the enzymatic activity of P5, suggesting that the reproduction tradeoff stems from other factors such as inefficient capsid assembly or disassembly. Our study demonstrates how combining experimental evolution, biochemistry, and structural biology can identify the mechanisms that drive the antagonistic pleiotropic phenotypes of an individual point mutation in the classic evolutionary tug-of-war between survival and reproduction.
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Affiliation(s)
- Moshe Dessau
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, United States of America
| | - Daniel Goldhill
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States of America
| | - Robert L. McBride
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States of America
| | - Paul E. Turner
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States of America
| | - Yorgo Modis
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, United States of America
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132
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Unique motifs and hydrophobic interactions shape the binding of modified DNA ligands to protein targets. Proc Natl Acad Sci U S A 2012; 109:19971-6. [PMID: 23139410 DOI: 10.1073/pnas.1213933109] [Citation(s) in RCA: 183] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Selection of aptamers from nucleic acid libraries by in vitro evolution represents a powerful method of identifying high-affinity ligands for a broad range of molecular targets. Nevertheless, a sizeable fraction of proteins remain difficult targets due to inherently limited chemical diversity of nucleic acids. We have exploited synthetic nucleotide modifications that confer protein-like diversity on a nucleic acid scaffold, resulting in a new generation of binding reagents called SOMAmers (Slow Off-rate Modified Aptamers). Here we report a unique crystal structure of a SOMAmer bound to its target, platelet-derived growth factor B (PDGF-BB). The SOMAmer folds into a compact structure and exhibits a hydrophobic binding surface that mimics the interface between PDGF-BB and its receptor, contrasting sharply with mainly polar interactions seen in traditional protein-binding aptamers. The modified nucleotides circumvent the intrinsic diversity constraints of natural nucleic acids, thereby greatly expanding the structural vocabulary of nucleic acid ligands and considerably broadening the range of accessible protein targets.
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133
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Berman HM. Creating a community resource for protein science. Protein Sci 2012; 21:1587-96. [PMID: 22969036 PMCID: PMC3527698 DOI: 10.1002/pro.2154] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Accepted: 08/30/2012] [Indexed: 12/13/2022]
Abstract
In addition to being one of the early pioneers in protein crystallography, Carl Brändén made significant contributions to science education with his elegant and beautifully illustrated book Introduction to Protein Structure (Brändén and Tooze, New York: Garland, 1991). It is truly an honor to receive this award in their names. This award and the 40th anniversary of the Protein Data Bank (PDB; Berman et al., Structure 2012;20:391-396) have given me an opportunity to reflect on the various components that have contributed to building a resource for protein science and to try to quantify the impact of having PDB data openly available.
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Affiliation(s)
- Helen M Berman
- Department of Chemistry and Chemical Biology, Center for Integrative Proteomics Research, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA.
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134
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Kawasaki Y, Yasukawa K, Inouye K. Effects of site-directed mutagenesis in the N-terminal domain of thermolysin on its stabilization. J Biochem 2012; 153:85-92. [PMID: 23087322 DOI: 10.1093/jb/mvs126] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The thermolysin variant G8C/N60C/S65P in which the triple mutation in the N-terminal domain, Gly8→Cys/Asn60→Cys/Ser65→Pro, is undertaken increases stability [Yasukawa, K. and Inouye, K. (2007) Improving the activity and stability of thermolysin by site-directed mutagenesis. Biochim. Biophys. Acta 1774, 1281-1288] and its mechanism is examined in this study. The apparent denaturing temperatures based on ellipticity at 222 nm of the wild-type thermolysin (WT), G8C/N60C, S65P and G8C/N60C/S65P were 85, >95, 88 and >95°C, respectively. The first-order rate constants, k(obs), of the thermal inactivation of WT and variants at 10 mM CaCl₂ increased with increasing thermal treatment temperatures (70-95°C), and those at 80°C decreased with increasing CaCl₂ concentrations (1-100 mM). The k(obs) values were in the order of WT > S65P > G8C/N60C≒G8C/N60C/S65P at all temperatures and CaCl₂ concentrations. These results indicate that the mutational combination, Gly8→Cys/Asn60→Cys and Ser65→Pro, increases stability only as high as Gly8→Cys/Asn60→Cys does. Assuming that irreversible inactivation of thermolysin occurs only in the absence of calcium ions, the dissociation constants, K(d), to the calcium ions of WT, G8C/N60C, S65P and G8C/N60C/S65P were 47, 8.9, 17 and 7.2 mM, respectively, suggesting that Gly8→Cys/Asn60→Cys and Ser65→Pro stabilize thermolysin by improving its affinity to calcium ions, most probably the one at the Ca²⁺-binding site III in the N-terminal domain.
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Affiliation(s)
- Yuichi Kawasaki
- Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
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135
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Dadarlat VM, Gorenstein LA, Post CB. Prediction of protein relative enthalpic stability from molecular dynamics simulations of the folded and unfolded states. Biophys J 2012; 103:1762-73. [PMID: 23083720 DOI: 10.1016/j.bpj.2012.08.048] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Revised: 08/01/2012] [Accepted: 08/17/2012] [Indexed: 11/18/2022] Open
Abstract
For proteins of known structure, the relative enthalpic stability with respect to wild-type, ΔΔH(U), can be estimated by direct computation of the folded and unfolded state energies. We propose a model by which the change in stability upon mutation can be predicted from all-atom molecular dynamics simulations for the folded state and a peptide-based model for the unfolded state. The unfolding enthalpies are expressed in terms of environmental and hydration-solvent reorganization contributions that readily allow a residue-specific analysis of ΔΔH(U). The method is applied to estimate the relative enthalpic stability of variants with buried charged groups in T4 lysozyme. The predicted relative stabilities are in good agreement with experimental data. Environmental factors are observed to contribute more than hydration to the overall ΔΔH(U). The residue-specific analysis finds that the effects of burying charge are both localized and long-range. The enthalpy for hydration-solvent reorganization varies considerably among different amino-acid types, but because the variant folded state structures are similar to those of the wild-type, the hydration-solvent reorganization contribution to ΔΔH(U) is localized at the mutation site, in contrast to environmental contributions. Overall, mutation of apolar and polar amino acids to charged amino acids are destabilizing, but the reasons are complex and differ from site to site.
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Affiliation(s)
- Voichita M Dadarlat
- Markey Center for Structural Biology, Department of Medicinal Chemistry, Purdue University, West Lafayette, Indiana, USA
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136
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Engineering a model protein cavity to catalyze the Kemp elimination. Proc Natl Acad Sci U S A 2012; 109:16179-83. [PMID: 22988064 DOI: 10.1073/pnas.1208076109] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Synthetic cavitands and protein cavities have been widely studied as models for ligand recognition. Here we investigate the Met102 → His substitution in the artificial L99A cavity in T4 lysozyme as a Kemp eliminase. The resulting enzyme had k(cat)/K(M) = 0.43 M(-1) s(-1) and a (k(cat)/K(M))/k(uncat) = 10(7) at pH 5.0. The crystal structure of this enzyme was determined at 1.30 Å, as were the structures of four complexes of substrate and product analogs. The absence of ordered waters or hydrogen bonding interactions, and the presence of a common catalytic base (His102) in an otherwise hydrophobic, buried cavity, facilitated detailed analysis of the reaction mechanism and its optimization. Subsequent substitutions increased eliminase activity by an additional four-fold. As activity-enhancing substitutions were engineered into the cavity, protein stability decreased, consistent with the stability-function trade-off hypothesis. This and related model cavities may provide templates for studying protein design principles in radically simplified environments.
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137
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Risso VA, Acierno JP, Capaldi S, Monaco HL, Ermácora MR. X-ray evidence of a native state with increased compactness populated by tryptophan-less B. licheniformis β-lactamase. Protein Sci 2012; 21:964-76. [PMID: 22496053 DOI: 10.1002/pro.2076] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Revised: 03/25/2012] [Accepted: 03/29/2012] [Indexed: 11/12/2022]
Abstract
β-lactamases confer antibiotic resistance, one of the most serious world-wide health problems, and are an excellent theoretical and experimental model in the study of protein structure, dynamics and evolution. Bacillus licheniformis exo-small penicillinase (ESP) is a Class-A β-lactamase with three tryptophan residues located in the protein core. Here, we report the 1.7-Å resolution X-ray structure, catalytic parameters, and thermodynamic stability of ESP(ΔW), an engineered mutant of ESP in which phenylalanine replaces the wild-type tryptophan residues. The structure revealed no qualitative conformational changes compared with thirteen previously reported structures of B. licheniformis β-lactamases (RMSD = 0.4-1.2 Å). However, a closer scrutiny showed that the mutations result in an overall more compact structure, with most atoms shifted toward the geometric center of the molecule. Thus, ESP(ΔW) has a significantly smaller radius of gyration (R(g)) than the other B. licheniformis β-lactamases characterized so far. Indeed, ESP(ΔW) has the smallest R(g) among 126 Class-A β-lactamases in the Protein Data Bank (PDB). Other measures of compactness, like the number of atoms in fixed volumes and the number and average of noncovalent distances, confirmed the effect. ESP(ΔW) proves that the compactness of the native state can be enhanced by protein engineering and establishes a new lower limit to the compactness of the Class-A β-lactamase fold. As the condensation achieved by the native state is a paramount notion in protein folding, this result may contribute to a better understanding of how the sequence determines the conformational variability and thermodynamic stability of a given fold.
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Affiliation(s)
- Valeria A Risso
- Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Roque Sáenz Peña 325, 1876 Bernal, Buenos Aires, Argentina
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138
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Patzer SI, Albrecht R, Braun V, Zeth K. Structural and mechanistic studies of pesticin, a bacterial homolog of phage lysozymes. J Biol Chem 2012; 287:23381-96. [PMID: 22593569 PMCID: PMC3390615 DOI: 10.1074/jbc.m112.362913] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Yersinia pestis produces and secretes a toxin named pesticin that kills related bacteria of the same niche. Uptake of the bacteriocin is required for activity in the periplasm leading to hydrolysis of peptidoglycan. To understand the uptake mechanism and to investigate the function of pesticin, we combined crystal structures of the wild type enzyme, active site mutants, and a chimera protein with in vivo and in vitro activity assays. Wild type pesticin comprises an elongated N-terminal translocation domain, the intermediate receptor binding domain, and a C-terminal activity domain with structural analogy to lysozyme homologs. The full-length protein is toxic to bacteria when taken up to the target site via the outer or the inner membrane. Uptake studies of deletion mutants in the translocation domain demonstrate their critical size for import. To further test the plasticity of pesticin during uptake into bacterial cells, the activity domain was replaced by T4 lysozyme. Surprisingly, this replacement resulted in an active chimera protein that is not inhibited by the immunity protein Pim. Activity of pesticin and the chimera protein was blocked through introduction of disulfide bonds, which suggests unfolding as the prerequisite to gain access to the periplasm. Pesticin, a muramidase, was characterized by active site mutations demonstrating a similar but not identical residue pattern in comparison with T4 lysozyme.
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Affiliation(s)
- Silke I Patzer
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany
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139
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140
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Brown JW, Farelli JD, McKnight CJ. On the unyielding hydrophobic core of villin headpiece. Protein Sci 2012; 21:647-54. [PMID: 22467489 DOI: 10.1002/pro.2048] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Revised: 02/09/2012] [Accepted: 02/13/2012] [Indexed: 11/06/2022]
Abstract
Villin headpiece (HP67) is a small, autonomously-folding domain that has become a model system for understanding the fundamental tenets governing protein folding. In this communication, we explore the role that Leu61 plays in the structure and stability of the construct. Deletion of Leu61 results in a completely unfolded protein that cannot be expressed in Escherichia coli. Omission of only the aliphatic leucine side chain (HP67 L61G) perturbed neither the backbone conformation nor the orientation of local hydrophobic side chains. As a result, a large, solvent-exposed hydrophobic pocket, a negative replica of the leucine side-chain, was created on the surface. The loss of the hydrophobic interface between leucine 61 and the hydrophobic pocket destabilized the construct by ~3.3 kcal/mol. Insertion of a single glycine residue immediately before Leu61 (HP67 L61[GL]) was also highly destabilizing and had the effect of altering the backbone conformation (α-helix to π-helix) in order to precisely preserve the wild-type position and conformation of all hydrophobic residues, including Leu61. In addition to demonstrating that the hydrophobic side-chain of Leu61 is critically important for the stability of villin headpiece, our results are consistent with the notion that the precise interactions present within the hydrophobic core, rather than the hydrogen bonds that define the secondary structure, specify a protein's fold.
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Affiliation(s)
- Jeffrey W Brown
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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141
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Georgieva ER, Roy AS, Grigoryants VM, Borbat PP, Earle KA, Scholes CP, Freed JH. Effect of freezing conditions on distances and their distributions derived from Double Electron Electron Resonance (DEER): a study of doubly-spin-labeled T4 lysozyme. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 216:69-77. [PMID: 22341208 PMCID: PMC3323113 DOI: 10.1016/j.jmr.2012.01.004] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Revised: 01/10/2012] [Accepted: 01/11/2012] [Indexed: 05/11/2023]
Abstract
Pulsed dipolar ESR spectroscopy, DEER and DQC, require frozen samples. An important issue in the biological application of this technique is how the freezing rate and concentration of cryoprotectant could possibly affect the conformation of biomacromolecule and/or spin-label. We studied in detail the effect of these experimental variables on the distance distributions obtained by DEER from a series of doubly spin-labeled T4 lysozyme mutants. We found that the rate of sample freezing affects mainly the ensemble of spin-label rotamers, but the distance maxima remain essentially unchanged. This suggests that proteins frozen in a regular manner in liquid nitrogen faithfully maintain the distance-dependent structural properties in solution. We compared the results from rapidly freeze-quenched (≤100 μs) samples to those from commonly shock-frozen (slow freeze, 1 s or longer) samples. For all the mutants studied we obtained inter-spin distance distributions, which were broader for rapidly frozen samples than for slowly frozen ones. We infer that rapid freezing trapped a larger ensemble of spin label rotamers; whereas, on the time-scale of slower freezing the protein and spin-label achieve a population showing fewer low-energy conformers. We used glycerol as a cryoprotectant in concentrations of 10% and 30% by weight. With 10% glycerol and slow freezing, we observed an increased slope of background signals, which in DEER is related to increased local spin concentration, in this case due to insufficient solvent vitrification, and therefore protein aggregation. This effect was considerably suppressed in slowly frozen samples containing 30% glycerol and rapidly frozen samples containing 10% glycerol. The assignment of bimodal distributions to tether rotamers as opposed to protein conformations is aided by comparing results using MTSL and 4-Bromo MTSL spin-labels. The latter usually produce narrower distance distributions.
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Affiliation(s)
- Elka R Georgieva
- Department of Chemistry and Chemical Biology and ACERT, Cornell University, Ithaca, NY 14853, United States.
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142
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Lee M, Urata SM, Aguilera JA, Perry CC, Milligan JR. Modeling the Influence of Histone Proteins on the Sensitivity of DNA to Ionizing Radiation. Radiat Res 2012; 177:152-63. [DOI: 10.1667/rr2812.1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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143
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Braun LJ, Eldridge AM, Cummiskey J, Arthur KK, Wuttke DS. The role of adjuvant in mediating antigen structure and stability. J Pharm Sci 2011; 101:1391-9. [PMID: 22213631 DOI: 10.1002/jps.23039] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Revised: 12/07/2011] [Accepted: 12/13/2011] [Indexed: 11/08/2022]
Abstract
The purpose of this study was to probe the fate of a model antigen, a cysteine-free mutant of bacteriophage T4 lysozyme, to the level of fine structural detail, as a consequence of its interaction with an aluminum (Al)-containing adjuvant. Fluorescence spectroscopy and differential scanning calorimetry were used to compare the thermal stability of the protein in solution versus adsorbed onto an Al-containing adjuvant. Differences in accessible hydrophobic surface areas were investigated using an extrinsic fluorescence probe, 8-Anilino-1-naphthalenesulfonic acid (ANS). As has been observed with other model antigens, the apparent thermal stability of the protein decreased following adsorption onto the adjuvant. ANS spectra suggested that adsorption onto the adjuvant caused an increase in exposure of hydrophobic regions of the protein. Electrostatic interactions drove the adsorption, and disruption of these interactions with high ionic strength buffers facilitated the collection of two-dimensional (15) N heteronuclear single quantum coherence nuclear magnetic resonance data of protein released from the adjuvant. Although the altered stability of the adsorbed protein suggested changes to the protein's structure, the fine structure of the desorbed protein was nearly identical to the protein's structure in the adjuvant-free formulation. Thus, the adjuvant-induced changes to the protein that were responsible for the reduced thermal stability were not observed upon desorption.
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Affiliation(s)
- Latoya Jones Braun
- Department of Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, USA.
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144
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Abstract
Proteins are synthesized by the ribosome and generally must fold to become functionally active. Although it is commonly assumed that the ribosome affects the folding process, this idea has been extremely difficult to demonstrate. We have developed an experimental system to investigate the folding of single ribosome-bound stalled nascent polypeptides with optical tweezers. In T4 lysozyme, synthesized in a reconstituted in vitro translation system, the ribosome slows the formation of stable tertiary interactions and the attainment of the native state relative to the free protein. Incomplete T4 lysozyme polypeptides misfold and aggregate when free in solution, but they remain folding-competent near the ribosomal surface. Altogether, our results suggest that the ribosome not only decodes the genetic information and synthesizes polypeptides, but also promotes efficient de novo attainment of the native state.
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Affiliation(s)
- Christian M. Kaiser
- Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720, USA
- Department of Physics, University of California, Berkeley, CA 94720, USA
| | - Daniel H. Goldman
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
| | - John D. Chodera
- Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720, USA
| | - Ignacio Tinoco
- Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720, USA
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
| | - Carlos Bustamante
- Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720, USA
- Department of Physics, University of California, Berkeley, CA 94720, USA
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
- Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, USA
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145
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Yamamoto M, Nakagawa K, Fujiwara K, Shimizu A, Ikeguchi M, Ikeguchi M. A Native Disulfide Stabilizes Non-Native Helical Structures in Partially Folded States of Equine β-Lactoglobulin. Biochemistry 2011; 50:10590-7. [DOI: 10.1021/bi2013239] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mio Yamamoto
- Department of Bioinformatics, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577,
Japan
| | - Kanako Nakagawa
- Department of Bioinformatics, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577,
Japan
| | - Kazuo Fujiwara
- Department of Bioinformatics, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577,
Japan
| | - Akio Shimizu
- Department of Environmental
Engineering for Symbiosis, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577, Japan
| | - Mitsunori Ikeguchi
- Department of Supramolecular Biology,
Graduate School of Nanobioscience, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Masamichi Ikeguchi
- Department of Bioinformatics, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577,
Japan
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146
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Gorlatova N, Chao K, Pal LR, Araj RH, Galkin A, Turko I, Moult J, Herzberg O. Protein characterization of a candidate mechanism SNP for Crohn's disease: the macrophage stimulating protein R689C substitution. PLoS One 2011; 6:e27269. [PMID: 22087277 PMCID: PMC3210151 DOI: 10.1371/journal.pone.0027269] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Accepted: 10/13/2011] [Indexed: 12/14/2022] Open
Abstract
High throughput genome wide associations studies (GWAS) are now identifying a large number of genome loci related to risk of common human disease. Each such locus presents a challenge in identifying the relevant underlying mechanism. Here we report the experimental characterization of a proposed causal single nucleotide polymorphism (SNP) in a locus related to risk of Crohn's disease and ulcerative colitis. The SNP lies in the MST1 gene encoding Macrophage Stimulating Protein (MSP), and results in an R689C amino acid substitution within the β-chain of MSP (MSPβ). MSP binding to the RON receptor tyrosine kinase activates signaling pathways involved in the inflammatory response. We have purified wild-type and mutant MSPβ proteins and compared biochemical and biophysical properties that might impact the MSP/RON signaling pathway. Surface plasmon resonance (SPR) binding studies showed that MSPβ R689C affinity to RON is approximately 10-fold lower than that of the wild-type MSPβ and differential scanning fluorimetry (DSF) showed that the thermal stability of the mutant MSPβ was slightly lower than that of wild-type MSPβ, by 1.6 K. The substitution was found not to impair the specific Arg483-Val484 peptide bond cleavage by matriptase-1, required for MSP activation, and mass spectrometry of tryptic fragments of the mutated protein showed that the free thiol introduced by the R689C mutation did not form an aberrant disulfide bond. Together, the studies indicate that the missense SNP impairs MSP function by reducing its affinity to RON and perhaps through a secondary effect on in vivo concentration arising from reduced thermodynamic stability, resulting in down-regulation of the MSP/RON signaling pathway.
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Affiliation(s)
- Natalia Gorlatova
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland, United States of America
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147
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Laganowsky A, Zhao M, Soriaga AB, Sawaya MR, Cascio D, Yeates TO. An approach to crystallizing proteins by metal-mediated synthetic symmetrization. Protein Sci 2011; 20:1876-90. [PMID: 21898649 DOI: 10.1002/pro.727] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Revised: 08/17/2011] [Accepted: 08/17/2011] [Indexed: 12/31/2022]
Abstract
Combining the concepts of synthetic symmetrization with the approach of engineering metal-binding sites, we have developed a new crystallization methodology termed metal-mediated synthetic symmetrization. In this method, pairs of histidine or cysteine mutations are introduced on the surface of target proteins, generating crystal lattice contacts or oligomeric assemblies upon coordination with metal. Metal-mediated synthetic symmetrization greatly expands the packing and oligomeric assembly possibilities of target proteins, thereby increasing the chances of growing diffraction-quality crystals. To demonstrate this method, we designed various T4 lysozyme (T4L) and maltose-binding protein (MBP) mutants and cocrystallized them with one of three metal ions: copper (Cu²⁺, nickel (Ni²⁺), or zinc (Zn²⁺). The approach resulted in 16 new crystal structures--eight for T4L and eight for MBP--displaying a variety of oligomeric assemblies and packing modes, representing in total 13 new and distinct crystal forms for these proteins. We discuss the potential utility of the method for crystallizing target proteins of unknown structure by engineering in pairs of histidine or cysteine residues. As an alternate strategy, we propose that the varied crystallization-prone forms of T4L or MBP engineered in this work could be used as crystallization chaperones, by fusing them genetically to target proteins of interest.
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Affiliation(s)
- Arthur Laganowsky
- Institute for Genomics and Proteomics, UCLA-DOE, Los Angeles, California 90095-1570, USA
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148
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Bouvignies G, Vallurupalli P, Hansen DF, Correia BE, Lange O, Bah A, Vernon RM, Dahlquist FW, Baker D, Kay LE. Solution structure of a minor and transiently formed state of a T4 lysozyme mutant. Nature 2011; 477:111-4. [PMID: 21857680 DOI: 10.1038/nature10349] [Citation(s) in RCA: 220] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Accepted: 06/30/2011] [Indexed: 11/09/2022]
Abstract
Proteins are inherently plastic molecules, whose function often critically depends on excursions between different molecular conformations (conformers). However, a rigorous understanding of the relation between a protein's structure, dynamics and function remains elusive. This is because many of the conformers on its energy landscape are only transiently formed and marginally populated (less than a few per cent of the total number of molecules), so that they cannot be individually characterized by most biophysical tools. Here we study a lysozyme mutant from phage T4 that binds hydrophobic molecules and populates an excited state transiently (about 1 ms) to about 3% at 25 °C (ref. 5). We show that such binding occurs only via the ground state, and present the atomic-level model of the 'invisible', excited state obtained using a combined strategy of relaxation-dispersion NMR (ref. 6) and CS-Rosetta model building that rationalizes this observation. The model was tested using structure-based design calculations identifying point mutants predicted to stabilize the excited state relative to the ground state. In this way a pair of mutations were introduced, inverting the relative populations of the ground and excited states and altering function. Our results suggest a mechanism for the evolution of a protein's function by changing the delicate balance between the states on its energy landscape. More generally, they show that our approach can generate and validate models of excited protein states.
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Affiliation(s)
- Guillaume Bouvignies
- Department of Molecular Genetics, The University of Toronto, Toronto, Ontario M5S 1A8, Canada
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149
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Abstract
The active sites of enzymes are lined with side chains whose dynamic, geometric, and chemical properties have been finely tuned relative to the corresponding residues in water. For example, the carboxylates of glutamate and aspartate are weakly basic in water but become strongly basic when dehydrated in enzymatic sites. The dehydration of the carboxylate, although intrinsically thermodynamically unfavorable, is achieved by harnessing the free energy of folding and substrate binding to reach the required basicity. Allosterically regulated enzymes additionally rely on the free energy of ligand binding to stabilize the protein in a catalytically competent state. We demonstrate the interplay of protein folding energetics and functional group tuning to convert calmodulin (CaM), a regulatory binding protein, into AlleyCat, an allosterically controlled eliminase. Upon binding Ca(II), native CaM opens a hydrophobic pocket on each of its domains. We computationally identified a mutant that (i) accommodates carboxylate as a general base within these pockets, (ii) interacts productively in the Michaelis complex with the substrate, and (iii) stabilizes the transition state for the reaction. Remarkably, a single mutation of an apolar residue at the bottom of an otherwise hydrophobic cavity confers catalytic activity on calmodulin. AlleyCat showed the expected pH-rate profile, and it was inactivated by mutation of its active site Glu to Gln. A variety of control mutants demonstrated the specificity of the design. The activity of this minimal 75-residue allosterically regulated catalyst is similar to that obtained using more elaborate computational approaches to redesign complex enzymes to catalyze the Kemp elimination reaction.
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150
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Schmid FX. Lessons about Protein Stability from in vitro Selections. Chembiochem 2011; 12:1501-7. [DOI: 10.1002/cbic.201100018] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Indexed: 11/07/2022]
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