1
|
Cea PA, Pérez M, Herrera SM, Muñoz SM, Fuentes-Ugarte N, Coche-Miranda J, Maturana P, Guixé V, Castro-Fernandez V. Deciphering Structural Traits for Thermal and Kinetic Stability across Protein Family Evolution through Ancestral Sequence Reconstruction. Mol Biol Evol 2024; 41:msae127. [PMID: 38913681 PMCID: PMC11229819 DOI: 10.1093/molbev/msae127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 05/17/2024] [Accepted: 06/17/2024] [Indexed: 06/26/2024] Open
Abstract
Natural proteins are frequently marginally stable, and an increase in environmental temperature can easily lead to unfolding. As a result, protein engineering to improve protein stability is an area of intensive research. Nonetheless, since there is usually a high degree of structural homology between proteins from thermophilic organisms and their mesophilic counterparts, the identification of structural determinants for thermoadaptation is challenging. Moreover, in many cases, it has become clear that the success of stabilization strategies is often dependent on the evolutionary history of a protein family. In the last few years, the use of ancestral sequence reconstruction (ASR) as a tool for elucidation of the evolutionary history of functional traits of a protein family has gained strength. Here, we used ASR to trace the evolutionary pathways between mesophilic and thermophilic kinases that participate in the biosynthetic pathway of vitamin B1 in bacteria. By combining biophysics approaches, X-ray crystallography, and molecular dynamics simulations, we found that the thermal stability of these enzymes correlates with their kinetic stability, where the highest thermal/kinetic stability is given by an increase in small hydrophobic amino acids that allow a higher number of interatomic hydrophobic contacts, making this type of interaction the main support for stability in this protein architecture. The results highlight the potential benefits of using ASR to explore the evolutionary history of protein sequence and structure to identify traits responsible for the kinetic and thermal stability of any protein architecture.
Collapse
Affiliation(s)
- Pablo A Cea
- Departamento de Biología, Facultad de Ciencias, Laboratorio de Bioquímica y Biología Molecular, Universidad de Chile, Santiago, Chile
| | - Myriam Pérez
- Departamento de Biología, Facultad de Ciencias, Laboratorio de Bioquímica y Biología Molecular, Universidad de Chile, Santiago, Chile
| | - Sixto M Herrera
- Departamento de Biología, Facultad de Ciencias, Laboratorio de Bioquímica y Biología Molecular, Universidad de Chile, Santiago, Chile
| | - Sebastián M Muñoz
- Departamento de Biología, Facultad de Ciencias, Laboratorio de Bioquímica y Biología Molecular, Universidad de Chile, Santiago, Chile
| | - Nicolás Fuentes-Ugarte
- Departamento de Biología, Facultad de Ciencias, Laboratorio de Bioquímica y Biología Molecular, Universidad de Chile, Santiago, Chile
| | - José Coche-Miranda
- Departamento de Biología, Facultad de Ciencias, Laboratorio de Bioquímica y Biología Molecular, Universidad de Chile, Santiago, Chile
| | - Pablo Maturana
- Departamento de Biología, Facultad de Ciencias, Laboratorio de Bioquímica y Biología Molecular, Universidad de Chile, Santiago, Chile
| | - Victoria Guixé
- Departamento de Biología, Facultad de Ciencias, Laboratorio de Bioquímica y Biología Molecular, Universidad de Chile, Santiago, Chile
| | - Victor Castro-Fernandez
- Departamento de Biología, Facultad de Ciencias, Laboratorio de Bioquímica y Biología Molecular, Universidad de Chile, Santiago, Chile
| |
Collapse
|
2
|
Hait S, Basu S, Kundu S. Charge reversal mutations in mesophilic-thermophilic orthologous protein pairs and their role in enhancing coulombic interaction energy. J Biomol Struct Dyn 2023; 41:1745-1752. [PMID: 34996344 DOI: 10.1080/07391102.2021.2024258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Proteins from thermophilic organisms are a matter of immense interest for decades because of its application in fields like de-novo protein design, thermostable variants of biocatalysts etc. Previous studies have found several sequence and structural adaptations related to thermal stability, while charge reversal study remains ignored. Here we address whether charge reversal mutations naturally occur in mesophilic-thermophilic/hyperthermophilic orthologous proteins. Do they contribute to thermal stability? Our systematic study on 1550 mesophilic-thermophilic/hyperthermophilic orthologous protein pairs with remarkable structural and topological similarity, shows gain in coulombic interaction energy in thermophilic/hyperthermophilic proteins at short range associated with partially exposed and buried charge reversal mutations, which may enhance thermostability. Our findings call forth its application in future protein engineering studies. Communicated by Ramaswamy H. Sarma.
Collapse
Affiliation(s)
- Suman Hait
- Department of Biophysics, Molecular Biology and Bioinformatics, University of Calcutta, Kolkata, India
| | - Sudipto Basu
- Department of Biophysics, Molecular Biology and Bioinformatics, University of Calcutta, Kolkata, India
| | - Sudip Kundu
- Department of Biophysics, Molecular Biology and Bioinformatics, University of Calcutta, Kolkata, India
| |
Collapse
|
3
|
Van Wyk JC, Sewell BT, Danson MJ, Tsekoa TL, Sayed MF, Cowan DA. Engineering enhanced thermostability into the Geobacillus pallidus nitrile hydratase. Curr Res Struct Biol 2022; 4:256-270. [PMID: 36106339 PMCID: PMC9465369 DOI: 10.1016/j.crstbi.2022.07.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 06/27/2022] [Accepted: 07/19/2022] [Indexed: 11/20/2022] Open
Abstract
Nitrile hydratases (NHases) are important biocatalysts for the enzymatic conversion of nitriles to industrially-important amides such as acrylamide and nicotinamide. Although thermostability in this enzyme class is generally low, there is not sufficient understanding of its basis for rational enzyme design. The gene expressing the Co-type NHase from the moderate thermophile, Geobacillus pallidus RAPc8 (NRRL B-59396), was subjected to random mutagenesis. Four mutants were selected that were 3 to 15-fold more thermostable than the wild-type NHase, resulting in a 3.4–7.6 kJ/mol increase in the activation energy of thermal inactivation at 63 °C. High resolution X-ray crystal structures (1.15–1.80 Å) were obtained of the wild-type and four mutant enzymes. Mutant 9E, with a resolution of 1.15 Å, is the highest resolution crystal structure obtained for a nitrile hydratase to date. Structural comparisons between the wild-type and mutant enzymes illustrated the importance of salt bridges and hydrogen bonds in enhancing NHase thermostability. These additional interactions variously improved thermostability by increased intra- and inter-subunit interactions, preventing cooperative unfolding of α-helices and stabilising loop regions. Some hydrogen bonds were mediated via a water molecule, specifically highlighting the significance of structured water molecules in protein thermostability. Although knowledge of the mutant structures makes it possible to rationalize their behaviour, it would have been challenging to predict in advance that these mutants would be stabilising. Random mutagenesis yields a 15-fold increase in nitrile hydratase thermostability. Salt bridges and hydrogen bonds improves nitrile hydratase thermostability. Water-mediated hydrogen bonds improves protein thermostability.
Collapse
|
4
|
Boucher L, Somani S, Negron C, Ma W, Jacobs S, Chan W, Malia T, Obmolova G, Teplyakov A, Gilliland GL, Luo J. Surface salt bridges contribute to the extreme thermal stability of an FN3-like domain from a thermophilic bacterium. Proteins 2021; 90:270-281. [PMID: 34405904 DOI: 10.1002/prot.26218] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2020] [Revised: 03/08/2021] [Accepted: 08/02/2021] [Indexed: 12/27/2022]
Abstract
This study uses differential scanning calorimetry, X-ray crystallography, and molecular dynamics simulations to investigate the structural basis for the high thermal stability (melting temperature 97.5°C) of a FN3-like protein domain from thermophilic bacteria Thermoanaerobacter tengcongensis (FN3tt). FN3tt adopts a typical FN3 fold with a three-stranded beta sheet packing against a four-stranded beta sheet. We identified three solvent exposed arginine residues (R23, R25, and R72), which stabilize the protein through salt bridge interactions with glutamic acid residues on adjacent strands. Alanine mutation of the three arginine residues reduced melting temperature by up to 22°C. Crystal structures of the wild type (WT) and a thermally destabilized (∆Tm -19.7°C) triple mutant (R23L/R25T/R72I) were found to be nearly identical, suggesting that the destabilization is due to interactions of the arginine residues. Molecular dynamics simulations showed that the salt bridge interactions in the WT were stable and provided a dynamical explanation for the cooperativity observed between R23 and R25 based on calorimetry measurements. In addition, folding free energy changes computed using free energy perturbation molecular dynamics simulations showed high correlation with melting temperature changes. This work is another example of surface salt bridges contributing to the enhanced thermal stability of thermophilic proteins. The molecular dynamics simulation methods employed in this study may be broadly useful for in silico surface charge engineering of proteins.
Collapse
Affiliation(s)
- Lauren Boucher
- Janssen Research & Development, LLC, Spring House, Pennsylvania, USA
| | - Sandeep Somani
- Janssen Research & Development, LLC, Spring House, Pennsylvania, USA
| | | | - Wenting Ma
- Janssen Research & Development, LLC, Spring House, Pennsylvania, USA
| | - Steven Jacobs
- Janssen Research & Development, LLC, Spring House, Pennsylvania, USA
| | - Winnie Chan
- Janssen Research & Development, LLC, Spring House, Pennsylvania, USA
| | - Thomas Malia
- Janssen Research & Development, LLC, Spring House, Pennsylvania, USA
| | - Galina Obmolova
- Janssen Research & Development, LLC, Spring House, Pennsylvania, USA
| | - Alexey Teplyakov
- Janssen Research & Development, LLC, Spring House, Pennsylvania, USA
| | - Gary L Gilliland
- Janssen Research & Development, LLC, Spring House, Pennsylvania, USA
| | - Jinquan Luo
- Janssen Research & Development, LLC, Spring House, Pennsylvania, USA
| |
Collapse
|
5
|
Georgoulis A, Louka M, Mylonas S, Stavros P, Nounesis G, Vorgias CE. Consensus protein engineering on the thermostable histone-like bacterial protein HUs significantly improves stability and DNA binding affinity. Extremophiles 2020; 24:293-306. [PMID: 31980943 DOI: 10.1007/s00792-020-01154-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Accepted: 01/06/2020] [Indexed: 11/28/2022]
Abstract
Consensus-based protein engineering strategy has been applied to various proteins and it can lead to the design of proteins with enhanced biological performance. Histone-like HUs comprise a protein family with sequence variety within a highly conserved 3D-fold. HU function includes compacting and regulating bacterial DNA in a wide range of biological conditions in bacteria. To explore the possible impact of consensus-based design in the thermodynamic stability of HU proteins, the approach was applied using a dataset of sequences derived from a group of 40 mesostable, thermostable, and hyperthermostable HUs. The consensus-derived HU protein was named HUBest, since it is expected to perform best. The synthetic HU gene was overexpressed in E. coli and the recombinant protein was purified. Subsequently, HUBest was characterized concerning its correct folding and thermodynamic stability, as well as its ability to interact with plasmid DNA. A substantial increase in HUBest stability at high temperatures is observed. HUBest has significantly improved biological performance at ambience temperature, presenting very low Kd values for binding plasmid DNA as indicated from the Gibbs energy profile of HUBest. This Kd may be associated to conformational changes leading to decreased thermodynamic stability and, therefore, higher flexibility at ambient temperature.
Collapse
Affiliation(s)
- Anastasios Georgoulis
- Department of Biochemistry and Molecular Biology, National and Kapodistrian University of Athens, 157 01, Zografou, Greece
| | - Maria Louka
- Department of Biochemistry and Molecular Biology, National and Kapodistrian University of Athens, 157 01, Zografou, Greece
| | - Stratos Mylonas
- Department of Biochemistry and Molecular Biology, National and Kapodistrian University of Athens, 157 01, Zografou, Greece
| | - Philemon Stavros
- Biomolecular Physics Laboratory, INRASTES, National Centre for Scientific Research "Demokritos", 153 10, Agia Paraskevi, Greece
| | - George Nounesis
- Biomolecular Physics Laboratory, INRASTES, National Centre for Scientific Research "Demokritos", 153 10, Agia Paraskevi, Greece
| | - Constantinos E Vorgias
- Department of Biochemistry and Molecular Biology, National and Kapodistrian University of Athens, 157 01, Zografou, Greece.
| |
Collapse
|
6
|
Hait S, Mallik S, Basu S, Kundu S. Finding the generalized molecular principles of protein thermal stability. Proteins 2019; 88:788-808. [PMID: 31872464 DOI: 10.1002/prot.25866] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 12/05/2019] [Accepted: 12/14/2019] [Indexed: 11/09/2022]
Abstract
Are there any generalized molecular principles of thermal adaptation? Here, integrating the concepts of structural bioinformatics, sequence analysis, and classical knot theory, we develop a robust computational framework that seeks for mechanisms of thermal adaptation by comparing orthologous mesophilic-thermophilic and mesophilic-hyperthermophilic proteins of remarkable structural and topological similarities, and still leads us to context-independent results. A comprehensive analysis of 4741 high-resolution, non-redundant X-ray crystallographic structures collected from 11 hyperthermophilic, 32 thermophilic and 53 mesophilic prokaryotes unravels at least five "nearly universal" signatures of thermal adaptation, irrespective of the enormous sequence, structure, and functional diversity of the proteins compared. A careful investigation further extracts a set of amino acid changes that can potentially enhance protein thermal stability, and remarkably, these mutations are overrepresented in protein crystallization experiments, in disorder-to-order transitions and in engineered thermostable variants of existing mesophilic proteins. These results could be helpful to find a precise, global picture of thermal adaptation.
Collapse
Affiliation(s)
- Suman Hait
- Department of Biophysics, Molecular Biology and Bioinformatics, University of Calcutta, Kolkata, India
| | - Saurav Mallik
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Sudipto Basu
- Department of Biophysics, Molecular Biology and Bioinformatics, University of Calcutta, Kolkata, India.,Center of Excellence in Systems Biology and Biomedical Engineering (TEQIP Phase-III), University of Calcutta, Kolkata, India
| | - Sudip Kundu
- Department of Biophysics, Molecular Biology and Bioinformatics, University of Calcutta, Kolkata, India.,Center of Excellence in Systems Biology and Biomedical Engineering (TEQIP Phase-III), University of Calcutta, Kolkata, India
| |
Collapse
|
7
|
Bhattacharyya S, Mattiroli F, Luger K. Archaeal DNA on the histone merry-go-round. FEBS J 2018; 285:3168-3174. [PMID: 29729078 DOI: 10.1111/febs.14495] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 04/20/2018] [Accepted: 04/27/2018] [Indexed: 12/30/2022]
Abstract
How did the nucleosome, the fundamental building block of all eukaryotic chromatin, evolve? This central question has been impossible to address because the four core histones that make up the protein core of the nucleosome are so highly conserved in all eukaryotes. With the discovery of small, minimalist histone-like proteins in most known archaea, the likely origin of histones was identified. We recently determined the structure of an archaeal histone-DNA complex, revealing that archaeal DNA topology and protein-DNA interactions are astonishingly similar compared to the eukaryotic nucleosome. This was surprising since most archaeal histones form homodimers which consist only of the minimal histone fold and are devoid of histone tails and extensions. Unlike eukaryotic H2A-H2B and H3-H4 heterodimers that assemble into octameric particles wrapping ~ 150 bp DNA, archaeal histones form polymers around which DNA coils in a quasi-continuous superhelix. At any given point, this superhelix has the same geometry as nucleosomal DNA. This suggests that the architectural role of histones (i.e. the ability to bend DNA into a nucleosomal superhelix) was established before archaea and eukaryotes diverged, while the ability to form discrete particles, together with signaling functions of eukaryotic chromatin (i.e. epigenetic modifications) were secondary additions.
Collapse
Affiliation(s)
| | | | - Karolin Luger
- Howard Hughes Medical Institute, Boulder, CO, USA.,Department of Chemistry and Biochemistry, University of Colorado at Boulder, CO, USA
| |
Collapse
|
8
|
Zhou HX, Pang X. Electrostatic Interactions in Protein Structure, Folding, Binding, and Condensation. Chem Rev 2018; 118:1691-1741. [PMID: 29319301 DOI: 10.1021/acs.chemrev.7b00305] [Citation(s) in RCA: 485] [Impact Index Per Article: 80.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Charged and polar groups, through forming ion pairs, hydrogen bonds, and other less specific electrostatic interactions, impart important properties to proteins. Modulation of the charges on the amino acids, e.g., by pH and by phosphorylation and dephosphorylation, have significant effects such as protein denaturation and switch-like response of signal transduction networks. This review aims to present a unifying theme among the various effects of protein charges and polar groups. Simple models will be used to illustrate basic ideas about electrostatic interactions in proteins, and these ideas in turn will be used to elucidate the roles of electrostatic interactions in protein structure, folding, binding, condensation, and related biological functions. In particular, we will examine how charged side chains are spatially distributed in various types of proteins and how electrostatic interactions affect thermodynamic and kinetic properties of proteins. Our hope is to capture both important historical developments and recent experimental and theoretical advances in quantifying electrostatic contributions of proteins.
Collapse
Affiliation(s)
- Huan-Xiang Zhou
- Department of Chemistry and Department of Physics, University of Illinois at Chicago , Chicago, Illinois 60607, United States.,Department of Physics and Institute of Molecular Biophysics, Florida State University , Tallahassee, Florida 32306, United States
| | - Xiaodong Pang
- Department of Physics and Institute of Molecular Biophysics, Florida State University , Tallahassee, Florida 32306, United States
| |
Collapse
|
9
|
Sawle L, Huihui J, Ghosh K. All-Atom Simulations Reveal Protein Charge Decoration in the Folded and Unfolded Ensemble Is Key in Thermophilic Adaptation. J Chem Theory Comput 2017; 13:5065-5075. [DOI: 10.1021/acs.jctc.7b00545] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Lucas Sawle
- Department of Physics and
Astronomy, University of Denver, Denver, Colorado 80208, United States
| | - Jonathan Huihui
- Department of Physics and
Astronomy, University of Denver, Denver, Colorado 80208, United States
| | - Kingshuk Ghosh
- Department of Physics and
Astronomy, University of Denver, Denver, Colorado 80208, United States
| |
Collapse
|
10
|
Abstract
![]()
We review how major cell behaviors,
such as bacterial growth laws,
are derived from the physical chemistry of the cell’s proteins.
On one hand, cell actions depend on the individual biological functionalities
of their many genes and proteins. On the other hand, the common physics
among proteins can be as important as the unique biology that distinguishes
them. For example, bacterial growth rates depend strongly on temperature.
This dependence can be explained by the folding stabilities across
a cell’s proteome. Such modeling explains how thermophilic
and mesophilic organisms differ, and how oxidative damage of highly
charged proteins can lead to unfolding and aggregation in aging cells.
Cells have characteristic time scales. For example, E. coli can duplicate as fast as 2–3 times per hour. These time scales
can be explained by protein dynamics (the rates of synthesis and degradation,
folding, and diffusional transport). It rationalizes how bacterial
growth is slowed down by added salt. In the same way that the behaviors
of inanimate materials can be expressed in terms of the statistical
distributions of atoms and molecules, some cell behaviors can be expressed
in terms of distributions of protein properties, giving insights into
the microscopic basis of growth laws in simple cells.
Collapse
Affiliation(s)
- Kingshuk Ghosh
- Department of Physics and Astronomy, University of Denver , Denver, Colorado 80209, United States
| | - Adam M R de Graff
- Laufer Center for Physical and Quantitative Biology and Departments of Chemistry and Physics and Astronomy, Stony Brook University , Stony Brook, New York 11794, United States
| | - Lucas Sawle
- Department of Physics and Astronomy, University of Denver , Denver, Colorado 80209, United States
| | - Ken A Dill
- Laufer Center for Physical and Quantitative Biology and Departments of Chemistry and Physics and Astronomy, Stony Brook University , Stony Brook, New York 11794, United States
| |
Collapse
|
11
|
Batra J, Tjong H, Zhou HX. Electrostatic effects on the folding stability of FKBP12. Protein Eng Des Sel 2016; 29:301-308. [PMID: 27381026 PMCID: PMC4955870 DOI: 10.1093/protein/gzw014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Revised: 03/28/2016] [Accepted: 04/15/2016] [Indexed: 01/17/2023] Open
Abstract
The roles of electrostatic interactions in protein folding stability have been a matter of debate, largely due to the complexity in the theoretical treatment of these interactions. We have developed computational methods for calculating electrostatic effects on protein folding stability. To rigorously test and further refine these methods, here we carried out experimental studies into electrostatic effects on the folding stability of the human 12-kD FK506 binding protein (FKBP12). This protein has a close homologue, FKBP12.6, with amino acid substitutions in only 18 of their 107 residues. Of the 18 substitutions, 8 involve charged residues. Upon mutating FKBP12 residues at these 8 positions individually into the counterparts in FKBP12.6, the unfolding free energy (ΔGu) of FKBP12 changed by -0.3 to 0.7 kcal/mol. Accumulating stabilizing substitutions resulted in a mutant with a 0.9 kcal/mol increase in stability. Additional charge mutations were grafted from a thermophilic homologue, MtFKBP17, which aligns to FKBP12 with 31% sequence identity over 89 positions. Eleven such charge mutations were studied, with ΔΔGu varying from -2.9 to 0.1 kcal/mol. The predicted electrostatic effects by our computational methods with refinements herein had a root-mean-square deviation of 0.9 kcal/mol from the experimental ΔΔGu values on 16 single mutations of FKBP12. The difference in ΔΔGu between mutations grafted from FKBP12.6 and those from MtFKBP17 suggests that more distant homologues are less able to provide guidance for enhancing folding stability.
Collapse
Affiliation(s)
- Jyotica Batra
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA
- Present address: Department of Chemistry and Physics, Bellarmine University, 2001 Newburg Road, Louisville, KY40205, USA
| | - Harianto Tjong
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA
- Present address: Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Huan-Xiang Zhou
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA
| |
Collapse
|
12
|
Contribution of main chain and side chain atoms and their locations to the stability of thermophilic proteins. J Mol Graph Model 2016; 64:85-93. [DOI: 10.1016/j.jmgm.2016.01.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 01/03/2016] [Indexed: 11/21/2022]
|
13
|
Białobrzewski I, Mikš-Krajnik M, Dach J, Markowski M, Czekała W, Głuchowska K. Model of the sewage sludge-straw composting process integrating different heat generation capacities of mesophilic and thermophilic microorganisms. WASTE MANAGEMENT (NEW YORK, N.Y.) 2015; 43:72-83. [PMID: 26087644 DOI: 10.1016/j.wasman.2015.05.036] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Revised: 05/26/2015] [Accepted: 05/28/2015] [Indexed: 06/04/2023]
Abstract
A mathematical model integrating 11 first-order differential equations describing the dynamics of the aerobic composting process of sewage sludge was proposed. The model incorporates two microbial groups (mesophiles and thermophiles) characterized by different capacities of heat generation. Microbial growth rates, heat and mass transfer and degradation kinetics of the sewage sludge containing straw were modeled over a period of 36days. The coefficients of metabolic heat generation for mesophiles were 4.32×10(6) and 6.93×10(6)J/kg, for winter and summer seasons, respectively. However, for thermophiles, they were comparable for both seasons reaching 10.91×10(6) and 10.51×10(6)J/kg. In the model, significant parameters for microbial growth control were temperature and the content of easily hydrolysable substrate. The proposed model provided a satisfactory fit to experimental data captured for cuboid-shaped bioreactors with forced aeration. Model predictions of specific microbial populations and substrate decomposition were crucial for accurate description and understanding of sewage sludge composting.
Collapse
Affiliation(s)
- I Białobrzewski
- Department of Systems Engineering, Faculty of Technical Sciences, University of Warmia and Mazury in Olsztyn, Heweliusza 14, 10-718 Olsztyn, Poland.
| | - M Mikš-Krajnik
- Food Science and Technology Programme, c/o Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore(1); Chair of Industrial and Food Microbiology, Faculty of Food Sciences, University of Warmia and Mazury in Olsztyn, Plac Cieszyński 1, 10-726 Olsztyn, Poland(2)
| | - J Dach
- Institute of Biosystems Engineering, Poznan University of Life Sciences, Wojska Polskiego 50, 60-637 Poznan, Poland
| | - M Markowski
- Department of Systems Engineering, Faculty of Technical Sciences, University of Warmia and Mazury in Olsztyn, Heweliusza 14, 10-718 Olsztyn, Poland
| | - W Czekała
- Institute of Biosystems Engineering, Poznan University of Life Sciences, Wojska Polskiego 50, 60-637 Poznan, Poland
| | - K Głuchowska
- Department of General and Environmental Microbiology, Poznan University of Life Sciences, Szydłowska 50, 60-656 Poznan, Poland
| |
Collapse
|
14
|
Pezeshgi Modarres H, Dorokhov BD, Popov VO, Ravin NV, Skryabin KG, Dal Peraro M. Understanding and Engineering Thermostability in DNA Ligase from Thermococcus sp. 1519. Biochemistry 2015; 54:3076-85. [DOI: 10.1021/bi501227b] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hassan Pezeshgi Modarres
- Institute
of Bioengineering, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland
- Swiss Institute of Bioinformatics (SIB), Lausanne 1015, Switzerland
| | - Boris D. Dorokhov
- Centre
“Bioengineering”, Russian Academy of Sciences, Moscow 117312, Russia
| | - Vladimir O. Popov
- Bach
Institute of Biochemistry, Russian Academy of Sciences, Moscow 119071, Russia
- RSC “Kurchatov Institute”, Moscow 123182, Russia
| | - Nikolai V. Ravin
- Centre
“Bioengineering”, Russian Academy of Sciences, Moscow 117312, Russia
| | - Konstantin G. Skryabin
- Centre
“Bioengineering”, Russian Academy of Sciences, Moscow 117312, Russia
- RSC “Kurchatov Institute”, Moscow 123182, Russia
| | - Matteo Dal Peraro
- Institute
of Bioengineering, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland
- Swiss Institute of Bioinformatics (SIB), Lausanne 1015, Switzerland
| |
Collapse
|
15
|
Kalimeri M, Rahaman O, Melchionna S, Sterpone F. How conformational flexibility stabilizes the hyperthermophilic elongation factor G-domain. J Phys Chem B 2013; 117:13775-85. [PMID: 24087838 DOI: 10.1021/jp407078z] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Proteins from thermophilic organisms are stable and functional well above ambient temperature. Understanding the molecular mechanism underlying such a resistance is of crucial interest for many technological applications. For some time, thermal stability has been assumed to correlate with high mechanical rigidity of the protein matrix. In this work we address this common belief by carefully studying a pair of homologous G-domain proteins, with their melting temperatures differing by 40 K. To probe the thermal-stability content of the two proteins we use extensive simulations covering the microsecond time range and employ several different indicators to assess the salient features of the conformational landscape and the role of internal fluctuations at ambient condition. At the atomistic level, while the magnitude of fluctuations is comparable, the distribution of flexible and rigid stretches of amino-acids is more regular in the thermophilic protein causing a cage-like correlation of amplitudes along the sequence. This caging effect is suggested to favor stability at high T by confining the mechanical excitations. Moreover, it is found that the thermophilic protein, when folded, visits a higher number of conformational substates than the mesophilic homologue. The entropy associated with the occupation of the different substates and the thermal resilience of the protein intrinsic compressibility provide a qualitative insight on the thermal stability of the thermophilic protein as compared to its mesophilic homologue. Our findings potentially open the route to new strategies in the design of thermostable proteins.
Collapse
Affiliation(s)
- Maria Kalimeri
- Laboratoire de Biochimie Théorique, IBPC, CNRS, UPR9080, Université Paris Diderot , Sorbonne Paris Cité, France
| | | | | | | |
Collapse
|
16
|
Sedlmeier F, Netz RR. Solvation thermodynamics and heat capacity of polar and charged solutes in water. J Chem Phys 2013; 138:115101. [PMID: 23534665 DOI: 10.1063/1.4794153] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The solvation thermodynamics and in particular the solvation heat capacity of polar and charged solutes in water is studied using atomistic molecular dynamics simulations. As ionic solutes we consider a F(-) and a Na(+) ion, as an example for a polar molecule with vanishing net charge we take a SPC/E water molecule. The partial charges of all three solutes are varied in a wide range by a scaling factor. Using a recently introduced method for the accurate determination of the solvation free energy of polar solutes, we determine the free energy, entropy, enthalpy, and heat capacity of the three different solutes as a function of temperature and partial solute charge. We find that the sum of the solvation heat capacities of the Na(+) and F(-) ions is negative, in agreement with experimental observations, but our results uncover a pronounced difference in the heat capacity between positively and negatively charged groups. While the solvation heat capacity ΔC(p) stays positive and even increases slightly upon charging the Na(+) ion, it decreases upon charging the F(-) ion and becomes negative beyond an ion charge of q = -0.3e. On the other hand, the heat capacity of the overall charge-neutral polar solute derived from a SPC/E water molecule is positive for all charge scaling factors considered by us. This means that the heat capacity of a wide class of polar solutes with vanishing net charge is positive. The common ascription of negative heat capacities to polar chemical groups might arise from the neglect of non-additive interaction effects between polar and apolar groups. The reason behind this non-additivity is suggested to be related to the second solvation shell that significantly affects the solvation thermodynamics and due to its large spatial extent induces quite long-ranged interactions between solvated molecular parts and groups.
Collapse
Affiliation(s)
- Felix Sedlmeier
- Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| | | |
Collapse
|
17
|
Manjunath K, Sekar K. Molecular dynamics perspective on the protein thermal stability: a case study using SAICAR synthetase. J Chem Inf Model 2013; 53:2448-61. [PMID: 23962324 DOI: 10.1021/ci400306m] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The enzyme SAICAR synthetase ligates aspartate with CAIR (5'-phosphoribosyl-4-carboxy-5-aminoimidazole) forming SAICAR (5-amino-4-imidazole-N-succinocarboxamide ribonucleotide) in the presence of ATP. In continuation with our previous study on the thermostability of this enzyme in hyper-/thermophiles based on the structural aspects, here, we present the dynamic aspects that differentiate the mesophilic (E. coli, E. chaffeensis), thermophilic (G. kaustophilus), and hyperthermophilic (M. jannaschii, P. horikoshii) SAICAR synthetases by carrying out a total of 11 simulations. The five functional dimers from the above organisms were simulated using molecular dynamics for a period of 50 ns each at 300 K, 363 K, and an additional simulation at 333 K for the thermophilic protein. The basic features like root-mean-square deviations, root-mean-square fluctuations, surface accessibility, and radius of gyration revealed the instability of mesophiles at 363 K. Mean square displacements establish the reduced flexibility of hyper-/thermophiles at all temperatures. At the simulations time scale considered here, the long-distance networks are considerably affected in mesophilic structures at 363 K. In mesophiles, a comparatively higher number of short-lived (having less percent existence time) Cα, hydrogen bonds, hydrophobic interactions are formed, and long-lived (with higher percentage existence time) contacts are lost. The number of time-averaged salt-bridges is at least 2-fold higher in hyperthermophiles at 363 K. The change in surface accessibility of salt-bridges at 363 K from 300 K is nearly doubled in mesophilic protein compared to proteins from other temperature classes.
Collapse
Affiliation(s)
- Kavyashree Manjunath
- Supercomputer Education and Research Centre, Indian Institute of Science , Bangalore, Karnataka 560 012, India
| | | |
Collapse
|
18
|
Sterpone F, Melchionna S. Thermophilic proteins: insight and perspective from in silico experiments. Chem Soc Rev 2011; 41:1665-76. [PMID: 21975514 DOI: 10.1039/c1cs15199a] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Proteins from thermophilic and hyperthermophilic organisms are stable and function at high temperatures (50-100 °C). The importance of understanding the microscopic mechanisms underlying this thermal resistance is twofold: it is key for acquiring general clues on how proteins maintain their fold stable and for targeting those medical and industrial applications that aim at designing enzymes that can work under harsh conditions. In this tutorial review we first provide the general background of protein thermostability by specifically focusing on the structural and thermodynamic peculiarities; next, we discuss how computational studies based on Molecular Dynamics simulations can broaden and refine our knowledge on such special class of proteins.
Collapse
Affiliation(s)
- Fabio Sterpone
- Laboratoire de Biochimie Théorique, CNRS, UPR9080, Univ Paris Diderot, Sorbonne Paris Cité, 13 rue Pierre et Marie Curie, 75005, Paris, France.
| | | |
Collapse
|
19
|
Sawle L, Ghosh K. How do thermophilic proteins and proteomes withstand high temperature? Biophys J 2011; 101:217-27. [PMID: 21723832 PMCID: PMC3127178 DOI: 10.1016/j.bpj.2011.05.059] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Revised: 05/26/2011] [Accepted: 05/27/2011] [Indexed: 11/30/2022] Open
Abstract
We attempt to understand the origin of enhanced stability in thermophilic proteins by analyzing thermodynamic data for 116 proteins, the largest data set achieved to date. We compute changes in entropy and enthalpy at the convergence temperature where different driving forces are maximally decoupled, in contrast to the majority of previous studies that were performed at the melting temperature. We find, on average, that the gain in enthalpy upon folding is lower in thermophiles than in mesophiles, whereas the loss in entropy upon folding is higher in mesophiles than in thermophiles. This implies that entropic stabilization may be responsible for the high melting temperature, and hints at residual structure or compactness of the denatured state in thermophiles. We find a similar trend by analyzing a homologous set of proteins classified based only on the optimum growth temperature of the organisms from which they were extracted. We find that the folding free energy at the temperature of maximal stability is significantly more favorable in thermophiles than in mesophiles, whereas the maximal stability temperature itself is similar between these two classes. Furthermore, we extend the thermodynamic analysis to model the entire proteome. The results explain the high optimal growth temperature in thermophilic organisms and are in excellent quantitative agreement with full thermal growth rate data obtained in a dozen thermophilic and mesophilic organisms.
Collapse
Affiliation(s)
| | - Kingshuk Ghosh
- Department of Physics and Astronomy, University of Denver, Denver, Colorado
| |
Collapse
|
20
|
Chan CH, Yu TH, Wong KB. Stabilizing salt-bridge enhances protein thermostability by reducing the heat capacity change of unfolding. PLoS One 2011; 6:e21624. [PMID: 21720566 PMCID: PMC3123365 DOI: 10.1371/journal.pone.0021624] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2011] [Accepted: 06/03/2011] [Indexed: 11/19/2022] Open
Abstract
Most thermophilic proteins tend to have more salt bridges, and achieve higher thermostability by up-shifting and broadening their protein stability curves. While the stabilizing effect of salt-bridge has been extensively studied, experimental data on how salt-bridge influences protein stability curves are scarce. Here, we used double mutant cycles to determine the temperature-dependency of the pair-wise interaction energy and the contribution of salt-bridges to ΔCp in a thermophilic ribosomal protein L30e. Our results showed that the pair-wise interaction energies for the salt-bridges E6/R92 and E62/K46 were stabilizing and insensitive to temperature changes from 298 to 348 K. On the other hand, the pair-wise interaction energies between the control long-range ion-pair of E90/R92 were negligible. The ΔCp of all single and double mutants were determined by Gibbs-Helmholtz and Kirchhoff analyses. We showed that the two stabilizing salt-bridges contributed to a reduction of ΔCp by 0.8–1.0 kJ mol−1 K−1. Taken together, our results suggest that the extra salt-bridges found in thermophilic proteins enhance the thermostability of proteins by reducing ΔCp, leading to the up-shifting and broadening of the protein stability curves.
Collapse
Affiliation(s)
- Chi-Ho Chan
- School of Life Sciences, Centre for Protein Science and Crystallography, The Chinese University of Hong Kong, Hong Kong, Shatin, Hong Kong SAR, China
| | - Tsz-Ha Yu
- School of Life Sciences, Centre for Protein Science and Crystallography, The Chinese University of Hong Kong, Hong Kong, Shatin, Hong Kong SAR, China
| | - Kam-Bo Wong
- School of Life Sciences, Centre for Protein Science and Crystallography, The Chinese University of Hong Kong, Hong Kong, Shatin, Hong Kong SAR, China
- * E-mail:
| |
Collapse
|
21
|
Role of loop dynamics in thermal stability of mesophilic and thermophilic adenylosuccinate synthetase: a molecular dynamics and normal mode analysis study. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:630-7. [PMID: 21440684 DOI: 10.1016/j.bbapap.2011.03.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2010] [Revised: 02/19/2011] [Accepted: 03/18/2011] [Indexed: 01/28/2023]
Abstract
Enzymes from thermophiles are poorly active at temperatures at which their mesophilic homologs exhibit high activity and attain corresponding active states at high temperatures. In this study, comparative molecular dynamics (MD) simulations, supplemented by normal mode analysis, have been performed on an enzyme Adenylosuccinate synthetase (AdSS) from E. coli (mesophilic) and P. horikoshii (thermophilic) systems to understand the effects of loop dynamics on thermal stability of AdSS. In mesophilic AdSS, both ligand binding and catalysis are facilitated through the coordinated movement of five loops on the protein. The simulation results suggest that thermophilic P. horikoshii preserves structure and catalytic function at high temperatures by using the movement of only a subset of loops (two out of five) for ligand binding and catalysis unlike its mesophilic counterpart in E. coli. The pre-arrangement of the catalytic residues in P. horikoshii is well-preserved and salt bridges remain stable at high temperature (363K). The simulations suggest a general mechanism (including pre-arrangement of catalytic residues, increased polar residue content, stable salt bridges, increased rigidity, and fewer loop movements) used by thermophilic enzymes to preserve structure and be catalytically active at elevated temperatures.
Collapse
|
22
|
Fu H, Grimsley G, Scholtz JM, Pace CN. Increasing protein stability: importance of DeltaC(p) and the denatured state. Protein Sci 2010; 19:1044-52. [PMID: 20340133 DOI: 10.1002/pro.381] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Increasing the conformational stability of proteins is an important goal for both basic research and industrial applications. In vitro selection has been used successfully to increase protein stability, but more often site-directed mutagenesis is used to optimize the various forces that contribute to protein stability. In previous studies, we showed that improving electrostatic interactions on the protein surface and improving the beta-turn sequences were good general strategies for increasing protein stability, and used them to increase the stability of RNase Sa. By incorporating seven of these mutations in RNase Sa, we increased the stability by 5.3 kcal/mol. Adding one more mutation, D79F, gave a total increase in stability of 7.7 kcal/mol, and a melting temperature 28 degrees C higher than the wild-type enzyme. Surprisingly, the D79F mutation lowers the change in heat capacity for folding, DeltaC(p), by 0.6 kcal/mol/K. This suggests that this mutation stabilizes structure in the denatured state ensemble. We made other mutants that give some insight into the structure present in the denatured state. Finally, the thermodynamics of folding of these stabilized variants of RNase Sa are compared with those observed for proteins from thermophiles.
Collapse
Affiliation(s)
- Hailong Fu
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
| | | | | | | |
Collapse
|
23
|
Sterpone F, Bertonati C, Briganti G, Melchionna S. Water around thermophilic proteins: the role of charged and apolar atoms. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:284113. [PMID: 21399285 DOI: 10.1088/0953-8984/22/28/284113] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The thermal response of three proteins with mesophilic, thermophilic and hyperthermophilic character hints at the essential role played in thermostability by the protein-water interface. The formation of spanning water clusters enveloping the macromolecule and their resistance to thermal stress is shown to correlate with the charge distribution at the protein surface; in particular our findings suggest an effective role of the superficial charge distribution in stabilizing the global connectivity of the hydration water.
Collapse
Affiliation(s)
- Fabio Sterpone
- Department of Chemistry, Ecole Normale Superieure, 24 rue Lhomond, 75231 Paris Cedex 05, France
| | | | | | | |
Collapse
|
24
|
Merkley ED, Parson WW, Daggett V. Temperature dependence of the flexibility of thermophilic and mesophilic flavoenzymes of the nitroreductase fold. Protein Eng Des Sel 2010; 23:327-36. [PMID: 20083491 PMCID: PMC2851445 DOI: 10.1093/protein/gzp090] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Revised: 12/17/2009] [Accepted: 12/18/2009] [Indexed: 11/13/2022] Open
Abstract
A widely held hypothesis regarding the thermostability of thermophilic proteins states asserts that, at any given temperature, thermophilic proteins are more rigid than their mesophilic counterparts. Many experimental and computational studies have addressed this question with conflicting results. Here, we compare two homologous enzymes, one mesophilic (Escherichia coli FMN-dependent nitroreductase; NTR) and one thermophilic (Thermus thermophilus NADH oxidase; NOX), by multiple molecular dynamics simulations at temperatures from 5 to 100 degrees C. We find that the global rigidity/flexibility of the two proteins, assessed by a variety of metrics, is similar on the time scale of our simulations. However, the thermophilic enzyme retains its native conformation to a much greater degree at high temperature than does the mesophilic enzyme, both globally and within the active site. The simulations identify the helix F-helix G 'arm' as the region with the greatest difference in loss of native contacts between the two proteins with increasing temperature. In particular, a network of electrostatic interactions holds helix F to the body of the protein in the thermophilic protein, and this network is absent in the mesophilic counterpart.
Collapse
Affiliation(s)
- Eric D. Merkley
- Department of Biochemistry, University of Washington, Box 357350, Seattle, Washington 98195-7350, USA
| | - William W. Parson
- Department of Biochemistry, University of Washington, Box 357350, Seattle, Washington 98195-7350, USA
| | - Valerie Daggett
- Department of Biochemistry, University of Washington, Box 357350, Seattle, Washington 98195-7350, USA
- Department of Bioengineering, University of Washington, Box 355061, Seattle, WA 98195-5061, USA
| |
Collapse
|
25
|
Abstract
New amino acid sequences of proteins are being learned at a rapid rate, thanks to modern genomics. The native structures and functions of those proteins can often be inferred using bioinformatics methods. We show here that it is also possible to infer the stabilities and thermal folding properties of proteins, given only simple genomics information: the chain length and the numbers of charged side chains. In particular, our model predicts DeltaH(T), DeltaS(T), DeltaC(p), and DeltaF(T)--the folding enthalpy, entropy, heat capacity, and free energy--as functions of temperature T; the denaturant m values in guanidine and urea; the pH-temperature-salt phase diagrams, and the energy of confinement F(s) of the protein inside a cavity of radius s. All combinations of these phase equilibria can also then be computed from that information. As one illustration, we compute the pH and salt conditions that would denature a protein inside a small confined cavity. Because the model is analytical, it is computationally efficient enough that it could be used to automatically annotate whole proteomes with protein stability information.
Collapse
|
26
|
Sterpone F, Bertonati C, Briganti G, Melchionna S. Key Role of Proximal Water in Regulating Thermostable Proteins. J Phys Chem B 2008; 113:131-7. [DOI: 10.1021/jp805199c] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Fabio Sterpone
- Caspur, via dei Tizii 6B, 00185, Rome, Italy, and Department of Biochemical Sciences “Rossi Fanelli”, SOFT-INFM-CNR and Department of Physics, University of Rome La Sapienza, Ple. Aldo Moro 2, 00185, Rome, Italy
| | - Claudia Bertonati
- Caspur, via dei Tizii 6B, 00185, Rome, Italy, and Department of Biochemical Sciences “Rossi Fanelli”, SOFT-INFM-CNR and Department of Physics, University of Rome La Sapienza, Ple. Aldo Moro 2, 00185, Rome, Italy
| | - Giuseppe Briganti
- Caspur, via dei Tizii 6B, 00185, Rome, Italy, and Department of Biochemical Sciences “Rossi Fanelli”, SOFT-INFM-CNR and Department of Physics, University of Rome La Sapienza, Ple. Aldo Moro 2, 00185, Rome, Italy
| | - Simone Melchionna
- Caspur, via dei Tizii 6B, 00185, Rome, Italy, and Department of Biochemical Sciences “Rossi Fanelli”, SOFT-INFM-CNR and Department of Physics, University of Rome La Sapienza, Ple. Aldo Moro 2, 00185, Rome, Italy
| |
Collapse
|
27
|
Fernandes AT, Martins LO, Melo EP. The hyperthermophilic nature of the metallo-oxidase from Aquifex aeolicus. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1794:75-83. [PMID: 18930169 DOI: 10.1016/j.bbapap.2008.09.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2008] [Revised: 08/22/2008] [Accepted: 09/11/2008] [Indexed: 10/21/2022]
Abstract
The stability of the Aquifex aeolicus multicopper oxidase (McoA) was studied by spectroscopy, calorimetry and chromatography to understand its thermophilic nature. The enzyme is hyperthermostable as deconvolution of the differential scanning calorimetry trace shows that thermal unfolding is characterized by temperature values at the mid-point of 105, 110 and 114 degrees C. Chemical denaturation revealed however a very low stability at room temperature (2.8 kcal/mol) because copper bleaching/depletion occur before the unfolding of the tertiary structure and McoA is highly prone to aggregate. Indeed, unfolding kinetics measured with the stopped-flow technique quantified the stabilizing effect of copper on McoA (1.5 kcal/mol) and revealed quite an uncommon observation further confirmed by light scattering and gel filtration chromatography: McoA aggregates in the presence of guanidinium hydrochloride, i.e., under unfolding conditions. The aggregation process results from the accumulation of a quasi-native state of McoA that binds to ANS and is the main determinant of the stability curve of McoA. Kinetic partitioning between aggregation and unfolding leads to a very low heat capacity change and determines a flat dependence of stability on temperature.
Collapse
Affiliation(s)
- André T Fernandes
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, 2781-901 Oeiras, Portugal
| | | | | |
Collapse
|
28
|
Motono C, Gromiha MM, Kumar S. Thermodynamic and kinetic determinants ofThermotoga maritimacold shock protein stability: A structural and dynamic analysis. Proteins 2008; 71:655-69. [DOI: 10.1002/prot.21729] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
29
|
Haruki M, Tanaka M, Motegi T, Tadokoro T, Koga Y, Takano K, Kanaya S. Structural and thermodynamic analyses of Escherichia coli RNase HI variant with quintuple thermostabilizing mutations. FEBS J 2007; 274:5815-25. [DOI: 10.1111/j.1742-4658.2007.06104.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
30
|
Ruller R, Deliberto L, Ferreira TL, Ward RJ. Thermostable variants of the recombinant xylanase a from Bacillus subtilis produced by directed evolution show reduced heat capacity changes. Proteins 2007; 70:1280-93. [PMID: 17876824 DOI: 10.1002/prot.21617] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Directed evolution techniques have been used to improve the thermal stability of the xylanase A from Bacillus subtilis (XylA). Two generations of random mutant libraries generated by error prone PCR coupled with a single generation of DNA shuffling produced a series of mutant proteins with increasing thermostability. The most Thermostable XylA variant from the third generation contained four mutations Q7H, G13R, S22P, and S179C that showed an increase in melting temperature of 20 degrees C. The thermodynamic properties of a representative subset of nine XylA variants showing a range of thermostabilities were measured by thermal denaturation as monitored by the change in the far ultraviolet circular dichroism signal. Analysis of the data from these thermostable variants demonstrated a correlation between the decrease in the heat capacity change (deltaC(p)) with an increase in the midpoint of the transition temperature (T(m)) on transition from the native to the unfolded state. This result could not be interpreted within the context of the changes in accessible surface area of the protein on transition from the native to unfolded states. Since all the mutations are located at the surface of the protein, these results suggest that an explanation of the decrease in deltaC(p) should include effects arising from the protein/solvent interface.
Collapse
Affiliation(s)
- Roberto Ruller
- Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, FMRP-USP, Ribeirão Preto-SP, Universidade de São Paulo, São Paulo, Brazil
| | | | | | | |
Collapse
|
31
|
Dong F, Zhou HX. Electrostatic contribution to the binding stability of protein-protein complexes. Proteins 2006; 65:87-102. [PMID: 16856180 DOI: 10.1002/prot.21070] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
To investigate roles of electrostatic interactions in protein binding stability, electrostatic calculations were carried out on a set of 64 mutations over six protein-protein complexes. These mutations alter polar interactions across the interface and were selected for putative dominance of electrostatic contributions to the binding stability. Three protocols of implementing the Poisson-Boltzmann model were tested. In vdW4 the dielectric boundary between the protein low dielectric and the solvent high dielectric is defined as the protein van der Waals surface and the protein dielectric constant is set to 4. In SE4 and SE20, the dielectric boundary is defined as the surface of the protein interior inaccessible to a 1.4-A solvent probe, and the protein dielectric constant is set to 4 and 20, respectively. In line with earlier studies on the barnase-barstar complex, the vdW4 results on the large set of mutations showed the closest agreement with experimental data. The agreement between vdW4 and experiment supports the contention of dominant electrostatic contributions for the mutations, but their differences also suggest van der Waals and hydrophobic contributions. The results presented here will serve as a guide for future refinement in electrostatic calculation and inclusion of nonelectrostatic effects.
Collapse
Affiliation(s)
- Feng Dong
- Department of Physics, Drexel University, Philadelphia, Pennsylvania, USA
| | | |
Collapse
|
32
|
Melchionna S, Sinibaldi R, Briganti G. Explanation of the stability of thermophilic proteins based on unique micromorphology. Biophys J 2006; 90:4204-12. [PMID: 16533850 PMCID: PMC1459513 DOI: 10.1529/biophysj.105.078972] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Two mesophilic/thermophilic variants of the G-domain of the elongation factor Tu were studied via molecular dynamics simulations. By analyzing the simulation data via the Voronoi space tessellation, we have found that the two proteins have the same macromolecular packing, while the water-exposed surface area is larger for the thermophile. A larger coordination with water is probably due to a peculiar corrugation of the exposed surface of this species. From an enthalpic point of view, the thermophile shows a larger number of intramolecular hydrogen bonds, stronger electrostatic interactions, and a flatter free-energy landscape. Overall, the data suggest that the specific hydration state enhances macromolecular fluctuations but, at the same time, increases thermal stability.
Collapse
Affiliation(s)
- Simone Melchionna
- Istituto Nazionale di Fisica della Materia-SOFT, Department of Physics, Università di Roma La Sapienza, Rome, Italy.
| | | | | |
Collapse
|
33
|
Shiraki K, Nishikori S, Fujiwara S, Imanaka T, Takagi M. Contribution of protein-surface ion pairs of a hyperthermophilic protein on thermal and thermodynamic stability. J Biosci Bioeng 2005; 97:75-7. [PMID: 16233593 DOI: 10.1016/s1389-1723(04)70169-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2003] [Accepted: 10/02/2003] [Indexed: 11/30/2022]
Abstract
Hyperthermophilic proteins possess many ion pairs on their surface. To reveal the role of the ion pairs, O6-methylguanine-DNA methyltransferase from Thermococcus kodakaraensis KOD1 (Tk-MGMT) was studied as a model protein. The maximum free-energy changes of the protein in 0.1 and 0.5 M NaCl at pH 7.0 were 61.7 kJ mol(-1) at 31.5 degrees C and 77.4 kJ mol(-1) at 39.7 degrees C, respectively. On the other hand, mid points of the thermal unfolding temperatures in 0.1 and 0.5 M NaCl at pH 7.0 were 94.8 degrees C and 90.1 degrees C, respectively. The results suggest that the protein-surface ion pairs contribute to thermal stability (Tm), rather than thermodynamic stability (DeltaG).
Collapse
Affiliation(s)
- Kentaro Shiraki
- School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Tatsunokuchi, Ishikawa 923-1292, Japan
| | | | | | | | | |
Collapse
|
34
|
Lee CF, Allen MD, Bycroft M, Wong KB. Electrostatic interactions contribute to reduced heat capacity change of unfolding in a thermophilic ribosomal protein l30e. J Mol Biol 2005; 348:419-31. [PMID: 15811378 DOI: 10.1016/j.jmb.2005.02.052] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2004] [Revised: 02/23/2005] [Accepted: 02/23/2005] [Indexed: 10/25/2022]
Abstract
The origin of reduced heat capacity change of unfolding (DeltaC(p)) commonly observed in thermophilic proteins is controversial. The established theory that DeltaC(p) is correlated with change of solvent-accessible surface area cannot account for the large differences in DeltaC(p) observed for thermophilic and mesophilic homologous proteins, which are very similar in structures. We have determined the protein stability curves, which describe the temperature dependency of the free energy change of unfolding, for a thermophilic ribosomal protein L30e from Thermococcus celer, and its mesophilic homologue from yeast. Values of DeltaC(p), obtained by fitting the free energy change of unfolding to the Gibbs-Helmholtz equation, were 5.3 kJ mol(-1) K(-1) and 10.5 kJ mol(-1) K(-1) for T.celer and yeast L30e, respectively. We have created six charge-to-neutral mutants of T.celer L30e. Removal of charges at Glu6, Lys9, and Arg92 decreased the melting temperatures of T.celer L30e by approximately 3-9 degrees C, and the differences in melting temperatures were smaller with increasing concentration of salt. These results suggest that these mutations destabilize T.celer L30e by disrupting favorable electrostatic interactions. To determine whether electrostatic interactions contribute to the reduced DeltaC(p) of the thermophilic protein, we have determined DeltaC(p) for wild-type and mutant T.celer L30e by Gibbs-Helmholtz and by van't Hoff analyses. A concomitant increase in DeltaC(p) was observed for those charge-to-neutral mutants that destabilize T.celer L30e by removing favorable electrostatic interactions. The crystal structures of K9A, E90A, and R92A, were determined, and no structural change was observed. Taken together, our results support the conclusion that electrostatic interactions contribute to the reduced DeltaC(p) of T.celer L30e.
Collapse
Affiliation(s)
- Chi-Fung Lee
- Molecular Biotechnology Programme, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China
| | | | | | | |
Collapse
|
35
|
Ariza A, Richard DJ, White MF, Bond CS. Conformational flexibility revealed by the crystal structure of a crenarchaeal RadA. Nucleic Acids Res 2005; 33:1465-73. [PMID: 15755748 PMCID: PMC1062875 DOI: 10.1093/nar/gki288] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Homologous recombinational repair is an essential mechanism for repair of double-strand breaks in DNA. Recombinases of the RecA-fold family play a crucial role in this process, forming filaments that utilize ATP to mediate their interactions with single- and double-stranded DNA. The recombinase molecules present in the archaea (RadA) and eukaryota (Rad51) are more closely related to each other than to their bacterial counterpart (RecA) and, as a result, RadA makes a suitable model for the eukaryotic system. The crystal structure of Sulfolobus solfataricus RadA has been solved to a resolution of 3.2 Å in the absence of nucleotide analogues or DNA, revealing a narrow filamentous assembly with three molecules per helical turn. As observed in other RecA-family recombinases, each RadA molecule in the filament is linked to its neighbour via interactions of a short β-strand with the neighbouring ATPase domain. However, despite apparent flexibility between domains, comparison with other structures indicates conservation of a number of key interactions that introduce rigidity to the system, allowing allosteric control of the filament by interaction with ATP. Additional analysis reveals that the interaction specificity of the five human Rad51 paralogues can be predicted using a simple model based on the RadA structure.
Collapse
Affiliation(s)
| | - Derek J. Richard
- Centre for Biomolecular Sciences, University of St AndrewsNorth Haugh, St Andrews, KY16 9ST, UK
| | - Malcolm F. White
- Centre for Biomolecular Sciences, University of St AndrewsNorth Haugh, St Andrews, KY16 9ST, UK
| | - Charles S. Bond
- To whom correspondence should be addressed: Tel: +44 1382 348325; Fax: +44 1382 345764;
| |
Collapse
|
36
|
Abstract
The alpha-helix was the first proposed and experimentally confirmed secondary structure. The elegant simplicity of the alpha-helical structure, stabilized by hydrogen bonding between the backbone carbonyl oxygen and the peptide amide four residues away, has captivated the scientific community. In proteins, alpha-helices are also stabilized by the so-called capping interactions that occur at both the C- and the N-termini of the helix. This chapter provides a brief historical overview of the thermodynamic studies of the energetics of helix formation, and reviews recent progress in our understanding of the thermodynamics of helix formation.
Collapse
Affiliation(s)
- George I Makhatadze
- Department of Biochemistry and Molecular Biology, Penn State College of Medicine, Hershey, Pennsylvania 17033
| |
Collapse
|
37
|
Bastolla U, Moya A, Viguera E, van Ham RCHJ. Genomic determinants of protein folding thermodynamics in prokaryotic organisms. J Mol Biol 2004; 343:1451-66. [PMID: 15491623 DOI: 10.1016/j.jmb.2004.08.086] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2004] [Revised: 08/24/2004] [Accepted: 08/27/2004] [Indexed: 02/07/2023]
Abstract
Here we investigate how thermodynamic properties of orthologous proteins are influenced by the genomic environment in which they evolve. We performed a comparative computational study of 21 protein families in 73 prokaryotic species and obtained the following main results. (i) Protein stability with respect to the unfolded state and with respect to misfolding are anticorrelated. There appears to be a trade-off between these two properties, which cannot be optimized simultaneously. (ii) Folding thermodynamic parameters are strongly correlated with two genomic features, genome size and G+C composition. In particular, the normalized energy gap, an indicator of folding efficiency in statistical mechanical models of protein folding, is smaller in proteins of organisms with a small genome size and a compositional bias towards A+T. Such genomic features are characteristic for bacteria with an intracellular lifestyle. We interpret these correlations in light of mutation pressure and natural selection. A mutational bias toward A+T at the DNA level translates into a mutational bias toward more hydrophobic (and in general more interactive) proteins, a consequence of the structure of the genetic code. Increased hydrophobicity renders proteins more stable against unfolding but less stable against misfolding. Proteins with high hydrophobicity and low stability against misfolding occur in organisms with reduced genomes, like obligate intracellular bacteria. We argue that they are fixed because these organisms experience weaker purifying selection due to their small effective population sizes. This interpretation is supported by the observation of a high expression level of chaperones in these bacteria. Our results indicate that the mutational spectrum of a genome and the strength of selection significantly influence protein folding thermodynamics.
Collapse
Affiliation(s)
- Ugo Bastolla
- Centro de Astrobiología (CSIC-INTA), E-28850 Torrejón de Ardoz, Spain.
| | | | | | | |
Collapse
|
38
|
Kumar S, Nussinov R. Experiment-guided thermodynamic simulations on reversible two-state proteins: implications for protein thermostability. Biophys Chem 2004; 111:235-46. [PMID: 15501567 DOI: 10.1016/j.bpc.2004.06.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2004] [Revised: 05/27/2004] [Accepted: 06/01/2004] [Indexed: 11/27/2022]
Abstract
Here, we perform protein thermodynamic simulations within a set of boundary conditions, effectively blanketing the experimental data. The thermodynamic parameters, melting temperature (TG), enthalpy change at the melting temperature (DeltaHG) and heat capacity change (DeltaCp) were systematically varied over the experimentally observed ranges for small single domain reversible two-state proteins. Parameter sets that satisfy the Gibbs-Helmholtz equation and yield a temperature of maximal stability (TS) around room temperature were selected. The results were divided into three categories by arbitrarily chosen TG ranges. The TG ranges in these categories correspond to typical values of the melting temperatures observed for the majority of the proteins from mesophilic, thermophilic and hyperthermophilic organisms. As expected, DeltaCp values tend to be high in mesophiles and low in hyperthermophiles. An increase in TG is accompanied by an up-shift and broadening of the protein stability curves, however, with a large scatter. Furthermore, the simulations reveal that the average DeltaHG increases with TG up to approximately 360 K and becomes constant thereafter. DeltaCp decreases with TG with different rates before and after approximately 360 K. This provides further justification for the separate grouping of proteins into thermophiles and hyperthermophiles to assess their thermodynamic differences. This analysis of the Gibbs-Helmholtz equation has allowed us to study the interdependence of the thermodynamic parameters TG, DeltaHG and DeltaCp and their derivatives in a more rigorous way than possible by the limited experimental protein thermodynamics data available in the literature. The results provide new insights into protein thermostability and suggest potential strategies for its manipulation.
Collapse
Affiliation(s)
- Sandeep Kumar
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology Kanpur, Kanpur, U.P. 208016, India
| | | |
Collapse
|
39
|
Faria TQ, Lima JC, Bastos M, Maçanita AL, Santos H. Protein Stabilization by Osmolytes from Hyperthermophiles. J Biol Chem 2004; 279:48680-91. [PMID: 15347691 DOI: 10.1074/jbc.m408806200] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
2-O-alpha-Mannosylglycerate, a negatively charged osmolyte widely distributed among (hyper)thermophilic microorganisms, is known to provide notable protection to proteins against thermal denaturation. To study the mechanism responsible for protein stabilization, pico-second time-resolved fluorescence spectroscopy was used to characterize the thermal unfolding of a model protein, Staphylococcus aureus recombinant nuclease A (SNase), in the presence or absence of mannosylglycerate. The fluorescence decay times are signatures of the protein state, and the pre-exponential coefficients are used to evaluate the molar fractions of the folded and unfolded states. Hence, direct determination of equilibrium constants of unfolding from molar fractions was carried out. Van't Hoff plots of the equilibrium constants provided reliable thermodynamic data for SNase unfolding. Differential scanning calorimetry was used to validate this thermodynamic analysis. The presence of 0.5 m potassium mannosylglycerate caused an increase of 7 degrees C in the SNase melting temperature and a 2-fold increase in the unfolding heat capacity. Despite the considerable degree of stabilization rendered by this solute, the nature and population of protein states along unfolding were not altered in the presence of mannosylglycerate, denoting that the unfolding pathway of SNase was unaffected. The stabilization of SNase by mannosylglycerate arises from decreased unfolding entropy up to 65 degrees C and from an enthalpy increase above this temperature. In molecular terms, stabilization is interpreted as resulting from destabilization of the denatured state caused by preferential exclusion of the solute from the protein hydration shell upon unfolding, and stabilization of the native state by specific interactions. The physiological significance of charged solutes in hyperthermophiles is discussed.
Collapse
Affiliation(s)
- Tiago Q Faria
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Rua da Quinta Grande 6, Apartado 127, 2780-156 Oeiras, Portugal
| | | | | | | | | |
Collapse
|
40
|
Mikulecky PJ, Takach JC, Feig AL. Entropy-driven folding of an RNA helical junction: an isothermal titration calorimetric analysis of the hammerhead ribozyme. Biochemistry 2004; 43:5870-81. [PMID: 15134461 PMCID: PMC2465462 DOI: 10.1021/bi0360657] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Helical junctions are extremely common motifs in naturally occurring RNAs, but little is known about the thermodynamics that drive their folding. Studies of junction folding face several challenges: non-two-state folding behavior, superposition of secondary and tertiary structural energetics, and drastically opposing enthalpic and entropic contributions to folding. Here we describe a thermodynamic dissection of the folding of the hammerhead ribozyme, a three-way RNA helical junction, by using isothermal titration calorimetry of bimolecular RNA constructs. By using this method, we show that tertiary folding of the hammerhead core occurs with a highly unfavorable enthalpy change, and is therefore entropically driven. Furthermore, the enthalpies and heat capacities of core folding are the same whether supported by monovalent or divalent ions. These properties appear to be general to the core sequence of bimolecular hammerhead constructs. We present a model for the ion-induced folding of the hammerhead core that is similar to those advanced for the folding of much larger RNAs, involving ion-induced collapse to a structured, non-native state accompanied by rearrangement of core residues to produce the native fold. In agreement with previous enzymological and structural studies, our thermodynamic data suggest that the hammerhead structure is stabilized in vitro predominantly by diffusely bound ions. Our approach addresses several significant challenges that accompany the study of junction folding, and should prove useful in defining the thermodynamic determinants of stability in these important RNA motifs.
Collapse
Affiliation(s)
| | | | - Andrew L. Feig
- To whom correspondence should be addressed:Andrew L. Feig, Department of Chemistry, Indiana University, 800 E. Kirkwood Avenue, Bloomington, IN 47405 USA. Phone: 812-856-5449. Fax: 812-855-8300. E-mail:
| |
Collapse
|
41
|
Cowley AB, Rivera M, Benson DR. Stabilizing roles of residual structure in the empty heme binding pockets and unfolded states of microsomal and mitochondrial apocytochrome b5. Protein Sci 2004; 13:2316-29. [PMID: 15295112 PMCID: PMC2280026 DOI: 10.1110/ps.04817704] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2004] [Revised: 06/03/2004] [Accepted: 06/04/2004] [Indexed: 10/26/2022]
Abstract
The microsomal (Mc) and mitochondrial (OM) isoforms of mammalian cytochrome b5 are the products of different genes, which likely arose via duplication of a primordial gene and subsequent functional divergence. Despite sharing essentially identical folds, heme-polypeptide interactions are stronger in OM b5s than in Mc b5s due to the presence of two conserved patches of hydrophobic amino acid side chains in the OM heme binding pockets. This is of fundamental interest in terms of understanding heme protein structure-function relationships, because stronger heme-polypeptide interactions in OM b5s in comparison to Mc b5s may represent a key source of their more negative reduction potentials. Herein we provide evidence that interactions amongst the amino acid side chains contributing to the hydrophobic patches in rat OM (rOM) b5 persist when heme is removed, rendering the empty heme binding pocket of rOM apo-b5 more compact and less conformationally dynamic than that in bovine Mc (bMc) apo-b5. This may contribute to the stronger heme binding by OM apo-b5 by reducing the entropic penalty associated with polypeptide folding. We also show that when bMc apo-b5 unfolds it adopts a structure that is more compact and contains greater nonrandom secondary structure content than unfolded rOM apo-b5. We propose that a more robust beta-sheet in Mc apo-b5s compensates for the absence of the hydrophobic packing interactions that stabilize the heme binding pocket in OM apo-b5s.
Collapse
Affiliation(s)
- Aaron B Cowley
- Department of Chemistry, University of Kansas, 1251 Wescoe Hall Drive, 2010 Malott Hall, Lawrence, KS 66045-7582, USA
| | | | | |
Collapse
|
42
|
Ruiz-Sanz J, Filimonov VV, Christodoulou E, Vorgias CE, Mateo PL. Thermodynamic analysis of the unfolding and stability of the dimeric DNA-binding protein HU from the hyperthermophilic eubacterium Thermotoga maritima and its E34D mutant. ACTA ACUST UNITED AC 2004; 271:1497-507. [PMID: 15066175 DOI: 10.1111/j.1432-1033.2004.04057.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have studied the stability of the histone-like, DNA-binding protein HU from the hyperthermophilic eubacterium Thermotoga maritima and its E34D mutant by differential scanning microcalorimetry and CD under acidic conditions at various concentrations within the range of 2-225 micro m of monomer. The thermal unfolding of both proteins is highly reversible and clearly follows a two-state dissociation/unfolding model from the folded, dimeric state to the unfolded, monomeric one. The unfolding enthalpy is very low even when taking into account that the two disordered DNA-binding arms probably do not contribute to the cooperative unfolding, whereas the quite small value for the unfolding heat capacity change (3.7 kJ.K(-1).mol(-1)) stabilizes the protein within a broad temperature range, as shown by the stability curves (Gibbs energy functions vs. temperature), even though the Gibbs energy of unfolding is not very high either. The protein is stable at pH 4.00 and 3.75, but becomes considerably less so at pH 3.50 and below, to the point that a simple decrease in concentration will lead to unfolding of both the wild-type and the mutant protein at pH 3.50 and low temperatures. This indicates that various acid residues lose their charges leaving uncompensated positively charged clusters. The wild-type protein is more stable than its E34D mutant, particularly at pH 4.00 and 3.75 although less so at 3.50 (1.8, 1.6 and 0.6 kJ.mol(-1) at 25 degrees C for DeltaDeltaG at pH 4.00, 3.75 and 3.50, respectively), which seems to be related to the effect of a salt bridge between E34 and K13.
Collapse
Affiliation(s)
- Javier Ruiz-Sanz
- Department of Physical Chemistry, Faculty of Sciences, University of Granada, 18071 Granada, Spain
| | | | | | | | | |
Collapse
|
43
|
Dong F, Vijayakumar M, Zhou HX. Comparison of calculation and experiment implicates significant electrostatic contributions to the binding stability of barnase and barstar. Biophys J 2003; 85:49-60. [PMID: 12829463 PMCID: PMC1303064 DOI: 10.1016/s0006-3495(03)74453-1] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2002] [Accepted: 02/26/2003] [Indexed: 11/28/2022] Open
Abstract
The contributions of electrostatic interactions to the binding stability of barnase and barstar were studied by the Poisson-Boltzmann model with three different protocols: a), the dielectric boundary specified as the van der Waals (vdW) surface of the protein along with a protein dielectric constant (epsilon (p)) of 4; b), the dielectric boundary specified as the molecular (i.e., solvent-exclusion (SE)) surface along with epsilon (p) = 4; and c), "SE + epsilon (p) = 20." The "vdW + epsilon (p) = 4" and "SE + epsilon (p) = 20" protocols predicted an overall electrostatic stabilization whereas the "SE + epsilon (p) = 4" protocol predicted an overall electrostatic destabilization. The "vdW + epsilon (p) = 4" protocol was most consistent with experiment. It quantitatively reproduced the observed effects of 17 mutations neutralizing charged residues lining the binding interface and the measured coupling energies of six charge pairs across the interface and reasonably rationalized the experimental ionic strength and pH dependences of the binding constant. In contrast, the "SE + epsilon (p) = 4" protocol predicted significantly larger coupling energies of charge pairs whereas the "SE + epsilon (p) = 20" protocol did not predict any pH dependence. This study calls for further scrutiny of the different Poisson-Boltzmann protocols and demonstrates potential danger in drawing conclusions on electrostatic contributions based on a particular calculation protocol.
Collapse
Affiliation(s)
- Feng Dong
- Department of Physics, Florida State University, Tallahassee, Florida 32306, USA
| | | | | |
Collapse
|
44
|
Abstract
The thermophilic Bacillus caldolyticus cold shock protein (Bc-Csp) differs from the mesophilic Bacillus subtilis cold shock protein B (Bs-CspB) in 11 of the 66 residues. Stability measurements of Schmid and co-workers have implicated contributions of electrostatic interactions to the thermostability. To further elucidate the physical basis of the difference in stability, previously developed theoretical methods that treat electrostatic effects in both the folded and the unfolded states were used in this paper to study the effects of mutations, ionic strength, and temperature. For 27 mutations that narrow the difference in sequence between Bc-Csp and Bs-CspB, calculated changes in unfolding free energy (Delta G) and experimental results have a correlation coefficient of 0.98. Bc-Csp appears to use destabilization of the unfolded state by unfavorable charge-charge interactions as a mechanism for increasing stability. Accounting for the effects of ionic strength and temperature on the electrostatic free energies in both the folded and the unfolded states, explanations for two important experimental observations are presented. The disparate ionic strength dependences of Delta G for Bc-Csp and Bs-CspB were attributed to the difference in the total charges (-2e and -6e, respectively). A main contribution to the much higher unfolding entropy of Bs-CspB was found to come from the less favorable electrostatic interactions in the folded state. These results should provide insight for understanding the thermostability of other thermophilic proteins.
Collapse
Affiliation(s)
- Huan-Xiang Zhou
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306, USA.
| | | |
Collapse
|