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Triantafyllidis CP, Barberis A, Hartley F, Cuervo AM, Gjerga E, Charlton P, van Bijsterveldt L, Rodriguez JS, Buffa FM. A machine learning and directed network optimization approach to uncover TP53 regulatory patterns. iScience 2023; 26:108291. [PMID: 38047081 PMCID: PMC10692668 DOI: 10.1016/j.isci.2023.108291] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 07/21/2023] [Accepted: 10/18/2023] [Indexed: 12/05/2023] Open
Abstract
TP53, the Guardian of the Genome, is the most frequently mutated gene in human cancers and the functional characterization of its regulation is fundamental. To address this we employ two strategies: machine learning to predict the mutation status of TP53from transcriptomic data, and directed regulatory networks to reconstruct the effect of mutations on the transcipt levels of TP53 targets. Using data from established databases (Cancer Cell Line Encyclopedia, The Cancer Genome Atlas), machine learning could predict the mutation status, but not resolve different mutations. On the contrary, directed network optimization allowed to infer the TP53 regulatory profile across: (1) mutations, (2) irradiation in lung cancer, and (3) hypoxia in breast cancer, and we could observe differential regulatory profiles dictated by (1) mutation type, (2) deleterious consequences of the mutation, (3) known hotspots, (4) protein changes, (5) stress condition (irradiation/hypoxia). This is an important first step toward using regulatory networks for the characterization of the functional consequences of mutations, and could be extended to other perturbations, with implications for drug design and precision medicine.
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Affiliation(s)
- Charalampos P. Triantafyllidis
- Department of Oncology, Medical Sciences Division, University of Oxford, Oxford, UK
- Department of Epidemiology & Biostatistics, School of Public Health, Imperial College London, London, UK
| | - Alessandro Barberis
- Department of Oncology, Medical Sciences Division, University of Oxford, Oxford, UK
- Nuffield Department of Surgical Sciences, University of Oxford, Oxford, UK
| | - Fiona Hartley
- Department of Oncology, Medical Sciences Division, University of Oxford, Oxford, UK
| | - Ana Miar Cuervo
- Department of Oncology, Medical Sciences Division, University of Oxford, Oxford, UK
| | - Enio Gjerga
- Heidelberg University, Faculty of Medicine, Heidelberg University Hospital, Institute for Computational Biomedicine, Heidelberg, Germany
| | - Philip Charlton
- Department of Oncology, Medical Sciences Division, University of Oxford, Oxford, UK
| | | | - Julio Saez Rodriguez
- Heidelberg University, Faculty of Medicine, Heidelberg University Hospital, Institute for Computational Biomedicine, Heidelberg, Germany
| | - Francesca M. Buffa
- Department of Oncology, Medical Sciences Division, University of Oxford, Oxford, UK
- Department of Computing Sciences, BIDSA, Bocconi University, Milan, Italy
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2
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Qi R, Luo R. Robustness and Efficiency of Poisson-Boltzmann Modeling on Graphics Processing Units. J Chem Inf Model 2018; 59:409-420. [PMID: 30550277 DOI: 10.1021/acs.jcim.8b00761] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Poisson-Boltzmann equation (PBE) based continuum electrostatics models have been widely used in modeling electrostatic interactions in biochemical processes, particularly in estimating protein-ligand binding affinities. Fast convergence of PBE solvers is crucial in binding affinity computations as numerous snapshots need to be processed. Efforts have been reported to develop PBE solvers on graphics processing units (GPUs) for efficient modeling of biomolecules, though only relatively simple successive over-relaxation and conjugate gradient methods were implemented. However, neither convergence nor scaling properties of the two methods are optimal for large biomolecules. On the other hand, geometric multigrid (MG) has been shown to be an optimal solver on CPUs, though no MG have been reported for biomolecular applications on GPUs. This is not a surprise as it is a more complex method and depends on simpler but limited iterative methods such as Gauss-Seidel in its core relaxation procedure. The robustness and efficiency of MG on GPUs are also unclear. Here we present an implementation and a thorough analysis of MG on GPUs. Our analysis shows that robustness is a more pronounced issue than efficiency for both MG and other tested solvers when the single precision is used for complex biomolecules. We further show how to balance robustness and efficiency utilizing MG's overall efficiency and conjugate gradient's robustness, pointing to a hybrid GPU solver with a good balance of efficiency and accuracy. The new PBE solver will significantly improve the computational throughput for a range of biomolecular applications on the GPU platforms.
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3
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Xiao L, Luo R. Exploring a multi-scale method for molecular simulation in continuum solvent model: Explicit simulation of continuum solvent as an incompressible fluid. J Chem Phys 2018; 147:214112. [PMID: 29221408 DOI: 10.1063/1.5016052] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We explored a multi-scale algorithm for the Poisson-Boltzmann continuum solvent model for more robust simulations of biomolecules. In this method, the continuum solvent/solute interface is explicitly simulated with a numerical fluid dynamics procedure, which is tightly coupled to the solute molecular dynamics simulation. There are multiple benefits to adopt such a strategy as presented below. At this stage of the development, only nonelectrostatic interactions, i.e., van der Waals and hydrophobic interactions, are included in the algorithm to assess the quality of the solvent-solute interface generated by the new method. Nevertheless, numerical challenges exist in accurately interpolating the highly nonlinear van der Waals term when solving the finite-difference fluid dynamics equations. We were able to bypass the challenge rigorously by merging the van der Waals potential and pressure together when solving the fluid dynamics equations and by considering its contribution in the free-boundary condition analytically. The multi-scale simulation method was first validated by reproducing the solute-solvent interface of a single atom with analytical solution. Next, we performed the relaxation simulation of a restrained symmetrical monomer and observed a symmetrical solvent interface at equilibrium with detailed surface features resembling those found on the solvent excluded surface. Four typical small molecular complexes were then tested, both volume and force balancing analyses showing that these simple complexes can reach equilibrium within the simulation time window. Finally, we studied the quality of the multi-scale solute-solvent interfaces for the four tested dimer complexes and found that they agree well with the boundaries as sampled in the explicit water simulations.
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Affiliation(s)
- Li Xiao
- Departments of Biomedical Engineering, University of California, Irvine, California 92697, USA
| | - Ray Luo
- Departments of Biomedical Engineering, University of California, Irvine, California 92697, USA
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4
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Wang C, Greene D, Xiao L, Qi R, Luo R. Recent Developments and Applications of the MMPBSA Method. Front Mol Biosci 2018; 4:87. [PMID: 29367919 PMCID: PMC5768160 DOI: 10.3389/fmolb.2017.00087] [Citation(s) in RCA: 332] [Impact Index Per Article: 55.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 11/30/2017] [Indexed: 12/23/2022] Open
Abstract
The Molecular Mechanics Poisson-Boltzmann Surface Area (MMPBSA) approach has been widely applied as an efficient and reliable free energy simulation method to model molecular recognition, such as for protein-ligand binding interactions. In this review, we focus on recent developments and applications of the MMPBSA method. The methodology review covers solvation terms, the entropy term, extensions to membrane proteins and high-speed screening, and new automation toolkits. Recent applications in various important biomedical and chemical fields are also reviewed. We conclude with a few future directions aimed at making MMPBSA a more robust and efficient method.
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Affiliation(s)
- Changhao Wang
- Chemical and Materials Physics Graduate Program, University of California, Irvine, Irvine, CA, United States
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, United States
- Department of Physics and Astronomy, University of California, Irvine, Irvine, CA, United States
| | - D'Artagnan Greene
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, United States
| | - Li Xiao
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, United States
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, United States
| | - Ruxi Qi
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, United States
| | - Ray Luo
- Chemical and Materials Physics Graduate Program, University of California, Irvine, Irvine, CA, United States
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, United States
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, United States
- Department of Chemical Engineering and Materials Science, University of California, Irvine, Irvine, CA, United States
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5
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Xiao L, Diao J, Greene D, Wang J, Luo R. A Continuum Poisson-Boltzmann Model for Membrane Channel Proteins. J Chem Theory Comput 2017; 13:3398-3412. [PMID: 28564540 PMCID: PMC5728381 DOI: 10.1021/acs.jctc.7b00382] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Membrane proteins constitute a large portion of the human proteome and perform a variety of important functions as membrane receptors, transport proteins, enzymes, signaling proteins, and more. Computational studies of membrane proteins are usually much more complicated than those of globular proteins. Here, we propose a new continuum model for Poisson-Boltzmann calculations of membrane channel proteins. Major improvements over the existing continuum slab model are as follows: (1) The location and thickness of the slab model are fine-tuned based on explicit-solvent MD simulations. (2) The highly different accessibilities in the membrane and water regions are addressed with a two-step, two-probe grid-labeling procedure. (3) The water pores/channels are automatically identified. The new continuum membrane model is optimized (by adjusting the membrane probe, as well as the slab thickness and center) to best reproduce the distributions of buried water molecules in the membrane region as sampled in explicit water simulations. Our optimization also shows that the widely adopted water probe of 1.4 Å for globular proteins is a very reasonable default value for membrane protein simulations. It gives the best compromise in reproducing the explicit water distributions in membrane channel proteins, at least in the water accessible pore/channel regions. Finally, we validate the new membrane model by carrying out binding affinity calculations for a potassium channel, and we observe good agreement with the experimental results.
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Affiliation(s)
| | | | | | - Junmei Wang
- Department of Pharmaceutical Sciences, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, United States
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Qi R, Botello-Smith WM, Luo R. Acceleration of Linear Finite-Difference Poisson-Boltzmann Methods on Graphics Processing Units. J Chem Theory Comput 2017; 13:3378-3387. [PMID: 28553983 DOI: 10.1021/acs.jctc.7b00336] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electrostatic interactions play crucial roles in biophysical processes such as protein folding and molecular recognition. Poisson-Boltzmann equation (PBE)-based models have emerged as widely used in modeling these important processes. Though great efforts have been put into developing efficient PBE numerical models, challenges still remain due to the high dimensionality of typical biomolecular systems. In this study, we implemented and analyzed commonly used linear PBE solvers for the ever-improving graphics processing units (GPU) for biomolecular simulations, including both standard and preconditioned conjugate gradient (CG) solvers with several alternative preconditioners. Our implementation utilizes the standard Nvidia CUDA libraries cuSPARSE, cuBLAS, and CUSP. Extensive tests show that good numerical accuracy can be achieved given that the single precision is often used for numerical applications on GPU platforms. The optimal GPU performance was observed with the Jacobi-preconditioned CG solver, with a significant speedup over standard CG solver on CPU in our diversified test cases. Our analysis further shows that different matrix storage formats also considerably affect the efficiency of different linear PBE solvers on GPU, with the diagonal format best suited for our standard finite-difference linear systems. Further efficiency may be possible with matrix-free operations and integrated grid stencil setup specifically tailored for the banded matrices in PBE-specific linear systems.
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Affiliation(s)
- Ruxi Qi
- Department of Molecular Biology and Biochemistry University of California , Irvine, California 92697-3900, United States
| | - Wesley M Botello-Smith
- Department of Molecular Biology and Biochemistry University of California , Irvine, California 92697-3900, United States
| | - Ray Luo
- Department of Molecular Biology and Biochemistry University of California , Irvine, California 92697-3900, United States
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7
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Wang C, Xiao L, Luo R. Numerical interpretation of molecular surface field in dielectric modeling of solvation. J Comput Chem 2017; 38:1057-1070. [PMID: 28318096 PMCID: PMC5464005 DOI: 10.1002/jcc.24782] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 01/10/2017] [Accepted: 02/20/2017] [Indexed: 11/07/2022]
Abstract
Continuum solvent models, particularly those based on the Poisson-Boltzmann equation (PBE), are widely used in the studies of biomolecular structures and functions. Existing PBE developments have been mainly focused on how to obtain more accurate and/or more efficient numerical potentials and energies. However to adopt the PBE models for molecular dynamics simulations, a difficulty is how to interpret dielectric boundary forces accurately and efficiently for robust dynamics simulations. This study documents the implementation and analysis of a range of standard fitting schemes, including both one-sided and two-sided methods with both first-order and second-order Taylor expansions, to calculate molecular surface electric fields to facilitate the numerical calculation of dielectric boundary forces. These efforts prompted us to develop an efficient approximated one-dimensional method, which is to fit the surface field one dimension at a time, for biomolecular applications without much compromise in accuracy. We also developed a surface-to-atom force partition scheme given a level set representation of analytical molecular surfaces to facilitate their applications to molecular simulations. Testing of these fitting methods in the dielectric boundary force calculations shows that the second-order methods, including the one-dimensional method, consistently perform among the best in the molecular test cases. Finally, the timing analysis shows the approximated one-dimensional method is far more efficient than standard second-order methods in the PBE force calculations. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Changhao Wang
- Chemical and Materials Physics Graduate Program, University of California, Irvine, California, 92697
- Department of Physics and Astronomy, University of California, Irvine, California, 92697
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California, 92697
| | - Li Xiao
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California, 92697
- Department of Biomedical Engineering, University of California, Irvine, California, 92697
| | - Ray Luo
- Chemical and Materials Physics Graduate Program, University of California, Irvine, California, 92697
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California, 92697
- Department of Biomedical Engineering, University of California, Irvine, California, 92697
- Department of Chemical Engineering and Materials Science, University of California, Irvine, California, 92697
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8
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Greene D, Botello-Smith WM, Follmer A, Xiao L, Lambros E, Luo R. Modeling Membrane Protein-Ligand Binding Interactions: The Human Purinergic Platelet Receptor. J Phys Chem B 2016; 120:12293-12304. [PMID: 27934233 PMCID: PMC5460638 DOI: 10.1021/acs.jpcb.6b09535] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Membrane proteins, due to their roles as cell receptors and signaling mediators, make prime candidates for drug targets. The computational analysis of protein-ligand binding affinities has been widely employed as a tool in rational drug design efforts. Although efficient implicit solvent-based methods for modeling globular protein-ligand binding have been around for many years, the extension of such methods to membrane protein-ligand binding is still in its infancy. In this study, we extended the widely used Amber/MMPBSA method to model membrane protein-ligand systems, and we used it to analyze protein-ligand binding for the human purinergic platelet receptor (P2Y12R), a prominent drug target in the inhibition of platelet aggregation for the prevention of myocardial infarction and stroke. The binding affinities, computed by the Amber/MMPBSA method using standard parameters, correlate well with experiment. A detailed investigation of these parameters was conducted to assess their impact on the accuracy of the method. These analyses show the importance of properly treating the nonpolar solvation interactions and the electrostatic polarization in the binding of nucleotide agonists and non-nucleotide antagonists to P2Y12R. On the basis of the crystal structures and the experimental conditions in the binding assay, we further hypothesized that the nucleotide agonists lose their bound magnesium ion upon binding to P2Y12R, and our computational study supports this hypothesis. Ultimately, this work illustrates the value of computational analysis in the interpretation of experimental binding reactions.
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Affiliation(s)
- D'Artagnan Greene
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697
| | - Wesley M. Botello-Smith
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697
- Chemical and Materials Physics Graduate Program, University of California, Irvine, CA 92697
- Department of Chemistry, University of California, Irvine, CA 92697
| | - Alec Follmer
- Department of Chemistry, University of California, Irvine, CA 92697
| | - Li Xiao
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697
- Department of Biomedical Engineering, University of California, Irvine, CA 92697
| | - Eleftherios Lambros
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697
| | - Ray Luo
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697
- Chemical and Materials Physics Graduate Program, University of California, Irvine, CA 92697
- Department of Biomedical Engineering, University of California, Irvine, CA 92697
- Department of Chemical Engineering and Materials Science, University of California, Irvine, CA 92697
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9
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Wang C, Nguyen PH, Pham K, Huynh D, Le TBN, Wang H, Ren P, Luo R. Calculating protein-ligand binding affinities with MMPBSA: Method and error analysis. J Comput Chem 2016; 37:2436-46. [PMID: 27510546 PMCID: PMC5018451 DOI: 10.1002/jcc.24467] [Citation(s) in RCA: 156] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 07/13/2016] [Indexed: 11/07/2022]
Abstract
Molecular Mechanics Poisson-Boltzmann Surface Area (MMPBSA) methods have become widely adopted in estimating protein-ligand binding affinities due to their efficiency and high correlation with experiment. Here different computational alternatives were investigated to assess their impact to the agreement of MMPBSA calculations with experiment. Seven receptor families with both high-quality crystal structures and binding affinities were selected. First the performance of nonpolar solvation models was studied and it was found that the modern approach that separately models hydrophobic and dispersion interactions dramatically reduces RMSD's of computed relative binding affinities. The numerical setup of the Poisson-Boltzmann methods was analyzed next. The data shows that the impact of grid spacing to the quality of MMPBSA calculations is small: the numerical error at the grid spacing of 0.5 Å is already small enough to be negligible. The impact of different atomic radius sets and different molecular surface definitions was further analyzed and weak influences were found on the agreement with experiment. The influence of solute dielectric constant was also analyzed: a higher dielectric constant generally improves the overall agreement with experiment, especially for highly charged binding pockets. The data also showed that the converged simulations caused slight reduction in the agreement with experiment. Finally the direction of estimating absolute binding free energies was briefly explored. Upon correction of the binding-induced rearrangement free energy and the binding entropy lost, the errors in absolute binding affinities were also reduced dramatically when the modern nonpolar solvent model was used, although further developments were apparently necessary to further improve the MMPBSA methods. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Changhao Wang
- Chemical and Materials Physics Graduate Program, Irvine, California, 92697
- Department of Molecular Biology and Biochemistry, Irvine, California, 92697
- Department of Physics and Astronomy, University of California, Irvine, California, 92697
| | - Peter H Nguyen
- Department of Molecular Biology and Biochemistry, Irvine, California, 92697
| | - Kevin Pham
- Department of Molecular Biology and Biochemistry, Irvine, California, 92697
| | - Danielle Huynh
- Department of Molecular Biology and Biochemistry, Irvine, California, 92697
| | | | - Hongli Wang
- Department of Molecular Biology and Biochemistry, Irvine, California, 92697
| | - Pengyu Ren
- Department of Biomedical Engineering, University of Texas, Austin, Texas, 78712
| | - Ray Luo
- Chemical and Materials Physics Graduate Program, Irvine, California, 92697.
- Department of Molecular Biology and Biochemistry, Irvine, California, 92697.
- Department of Chemical Engineering and Materials Science, Irvine, California, 92697.
- Department of Biomedical Engineering, University of California, Irvine, California, 92697.
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Koulgi S, Achalere A, Sonavane U, Joshi R. Investigating DNA Binding and Conformational Variation in Temperature Sensitive p53 Cancer Mutants Using QM-MM Simulations. PLoS One 2015; 10:e0143065. [PMID: 26579714 PMCID: PMC4651507 DOI: 10.1371/journal.pone.0143065] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 10/30/2015] [Indexed: 12/12/2022] Open
Abstract
The tp53 gene is found to be mutated in 50% of all the cancers. The p53 protein, a product of tp53 gene, is a multi-domain protein. It consists of a core DNA binding domain (DBD) which is responsible for its binding and transcription of downstream target genes. The mutations in p53 protein are responsible for creating cancerous conditions and are found to be occurring at a high frequency in the DBD region of p53. Some of these mutations are also known to be temperature sensitive (ts) in nature. They are known to exhibit partial or strong binding with DNA in the temperature range (298–306 K). Whereas, at 310 K and above they show complete loss in binding. We have analyzed the changes in binding and conformational behavior at 300 K and 310 K for three of the ts-mutants viz., V143A, R249S and R175H. QM-MM simulations have been performed on the wild type and the above mentioned ts-mutants for 30 ns each. The optimal estimate of free energy of binding for a particular number of interface hydrogen bonds was calculated using the maximum likelihood method as described by Chodera et. al (2007). This parameter has been observed to be able to mimic the binding affinity of the p53 ts-mutants at 300 K and 310 K. Thus the correlation between MM-GBSA free energy of binding and hydrogen bonds formed by the interface residues between p53 and DNA has revealed the temperature dependent nature of these mutants. The role of main chain dihedrals was obtained by performing dihedral principal component analysis (PCA). This analysis, suggests that the conformational variations in the main chain dihedrals (ϕ and ψ) of the p53 ts-mutants may have caused reduction in the overall stability of the protein. The solvent exposure of the side chains of the interface residues were found to hamper the binding of the p53 to the DNA. Solvent Accessible Surface Area (SASA) also proved to be a crucial property in distinguishing the conformers obtained at 300 K and 310 K for the three ts-mutants from the wild type at 300 K.
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Affiliation(s)
- Shruti Koulgi
- Bioinformatics Group, Center for Development of Advanced Computing (C-DAC), S.P.Pune University Campus, Pune, India
| | - Archana Achalere
- Bioinformatics Group, Center for Development of Advanced Computing (C-DAC), S.P.Pune University Campus, Pune, India
| | - Uddhavesh Sonavane
- Bioinformatics Group, Center for Development of Advanced Computing (C-DAC), S.P.Pune University Campus, Pune, India
| | - Rajendra Joshi
- Bioinformatics Group, Center for Development of Advanced Computing (C-DAC), S.P.Pune University Campus, Pune, India
- * E-mail:
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11
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Enhancing human spermine synthase activity by engineered mutations. PLoS Comput Biol 2013; 9:e1002924. [PMID: 23468611 PMCID: PMC3585406 DOI: 10.1371/journal.pcbi.1002924] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Accepted: 12/28/2012] [Indexed: 11/25/2022] Open
Abstract
Spermine synthase (SMS) is an enzyme which function is to convert spermidine into spermine. It was shown that gene defects resulting in amino acid changes of the wild type SMS cause Snyder-Robinson syndrome, which is a mild-to-moderate mental disability associated with osteoporosis, facial asymmetry, thin habitus, hypotonia, and a nonspecific movement disorder. These disease-causing missense mutations were demonstrated, both in silico and in vitro, to affect the wild type function of SMS by either destabilizing the SMS dimer/monomer or directly affecting the hydrogen bond network of the active site of SMS. In contrast to these studies, here we report an artificial engineering of a more efficient SMS variant by transferring sequence information from another organism. It is confirmed experimentally that the variant, bearing four amino acid substitutions, is catalytically more active than the wild type. The increased functionality is attributed to enhanced monomer stability, lowering the pKa of proton donor catalytic residue, optimized spatial distribution of the electrostatic potential around the SMS with respect to substrates, and increase of the frequency of mechanical vibration of the clefts presumed to be the gates toward the active sites. The study demonstrates that wild type SMS is not particularly evolutionarily optimized with respect to the reaction spermidine → spermine. Having in mind that currently there are no variations (non-synonymous single nucleotide polymorphism, nsSNP) detected in healthy individuals, it can be speculated that the human SMS function is precisely tuned toward its wild type and any deviation is unwanted and disease-causing. Proteins are constantly subjected to evolutionary pressure to assure the organism's survival and reproduction. At the same time, the proteins' amino acid sequence undergoes mutations, some of which may cause diseases while others may be reflecting natural differences within the population (non-synonymous single nucleotide polymorphism, nsSNP). In this study we examine the human spermine synthase (HsSMS), for which currently there are no nsSNPs, while rare disease mutations are known to cause Snyder-Robinson syndrome. What is so special with this protein? Maybe the HsSMS is so well optimized for its function that any change of the wild type sequence should be degrading its performance. To check such a possibility, we engineered a mutant of HsSMS with enhanced stability, electrostatic and mechanical properties. The mutant was confirmed experimentally to be a better enzyme than the wild type. Thus, the HsSMS is not evolutionally optimized with respect to its enzymatic reaction, its amino acid sequence differs only in sick individuals and so far its sequence was found to be identical in all healthy individuals. Therefore, it can be speculated that the HsSMS function is precisely tuned toward the wild type characteristics such so any deviation is unwanted and is disease-causing.
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12
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Analyzing effects of naturally occurring missense mutations. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2012; 2012:805827. [PMID: 22577471 PMCID: PMC3346971 DOI: 10.1155/2012/805827] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Revised: 02/01/2012] [Accepted: 02/01/2012] [Indexed: 11/17/2022]
Abstract
Single-point mutation in genome, for example, single-nucleotide polymorphism (SNP) or rare genetic mutation, is the change of a single nucleotide for another in the genome sequence. Some of them will produce an amino acid substitution in the corresponding protein sequence (missense mutations); others will not. This paper focuses on genetic mutations resulting in a change in the amino acid sequence of the corresponding protein and how to assess their effects on protein wild-type characteristics. The existing methods and approaches for predicting the effects of mutation on protein stability, structure, and dynamics are outlined and discussed with respect to their underlying principles. Available resources, either as stand-alone applications or webservers, are pointed out as well. It is emphasized that understanding the molecular mechanisms behind these effects due to these missense mutations is of critical importance for detecting disease-causing mutations. The paper provides several examples of the application of 3D structure-based methods to model the effects of protein stability and protein-protein interactions caused by missense mutations as well.
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13
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Barakat K, Issack BB, Stepanova M, Tuszynski J. Effects of temperature on the p53-DNA binding interactions and their dynamical behavior: comparing the wild type to the R248Q mutant. PLoS One 2011; 6:e27651. [PMID: 22110706 PMCID: PMC3218007 DOI: 10.1371/journal.pone.0027651] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Accepted: 10/21/2011] [Indexed: 12/20/2022] Open
Abstract
Background The protein p53 plays an active role in the regulation of cell cycle. In about half of human cancers, the protein is inactivated by mutations located primarily in its DNA-binding domain. Interestingly, a number of these mutations possess temperature-induced DNA-binding characteristics. A striking example is the mutation of Arg248 into glutamine or tryptophan. These mutants are defective for binding to DNA at 310 K although they have been shown to bind specifically to several p53 response elements at sub-physiological temperatures (298–306 K). Methodology/Principal Findings This important experimental finding motivated us to examine the effects of temperature on the structure and configuration of R248Q mutant and compare it to the wild type protein. Our aim is to determine how and where structural changes of mutant variants take place due to temperature changes. To answer these questions, we compared the mutant to the wild-type proteins from two different aspects. First, we investigated the systems at the atomistic level through their DNA-binding affinity, hydrogen bond networks and spatial distribution of water molecules. Next, we assessed changes in their long-lived conformational motions at the coarse-grained level through the collective dynamics of their side-chain and backbone atoms separately. Conclusions The experimentally observed effect of temperature on the DNA-binding properties of p53 is reproduced. Analysis of atomistic and coarse-grained data reveal that changes in binding are determined by a few key residues and provide a rationale for the mutant-loss of binding at physiological temperatures. The findings can potentially enable a rescue strategy for the mutant structure.
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Affiliation(s)
- Khaled Barakat
- Department of Physics, University of Alberta, Edmonton, Alberta, Canada
- Department of Engineering Mathematics and Physics, Fayoum University, Fayoum, Egypt
| | - Bilkiss B. Issack
- Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada
- National Institute for Nanotechnology, National Research Council, Edmonton, Alberta, Canada
| | - Maria Stepanova
- Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada
- National Institute for Nanotechnology, National Research Council, Edmonton, Alberta, Canada
| | - Jack Tuszynski
- Department of Physics, University of Alberta, Edmonton, Alberta, Canada
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada
- * E-mail:
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Impact of the 237th residue on the folding of human carbonic anhydrase II. Int J Mol Sci 2011; 12:2797-807. [PMID: 21686151 PMCID: PMC3116157 DOI: 10.3390/ijms12052797] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Revised: 04/07/2011] [Accepted: 04/12/2011] [Indexed: 02/08/2023] Open
Abstract
The deficiency of human carbonic anhydrase II (HCAII) has been recognized to be associated with a disease called CAII deficiency syndrome (CADS). Among the many mutations, the P237H mutation has been characterized to lead to a significant decrease in the activity of the enzyme and in the Gibbs free energy of folding. However, sequence alignment indicated that the 237th residue of CAII is not fully conserved across all species. The FoldX theoretical calculations suggested that this residue did not significantly contribute to the overall folding of HCAII, since all mutants had small ΔΔG values (around 1 kcal/mol). The experimental determination indicated that at least three mutations affect HCAII folding significantly and the P237H mutation was the most deleterious one, suggesting that Pro237 was important to HCAII folding. The discrepancy between theoretical and experimental results suggested that caution should be taken when using the prediction methods to evaluate the details of disease-related mutations.
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15
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Guo Y, Yuan C, Tian F, Huang K, Weghorst CM, Tsai MD, Li J. Contributions of conserved TPLH tetrapeptides to the conformational stability of ankyrin repeat proteins. J Mol Biol 2010; 399:168-81. [PMID: 20398677 DOI: 10.1016/j.jmb.2010.04.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Revised: 03/27/2010] [Accepted: 04/06/2010] [Indexed: 01/11/2023]
Abstract
Ankyrin repeat (AR) proteins are one of the most abundant classes of repeat proteins and are involved in numerous physiological processes. These proteins are composed of various numbers of AR motifs stacked in a nearly linear fashion to adopt an elongated and nonglobular architecture. One salient feature prevalent in such a structural unit is the TPLH tetrapeptide or a close variant, T/SxxH, which initiates the helix-turn-helix conformation and presumably contributes to conformational stability through a hydrogen-bonding network. In the present study, we investigated the roles of T/SxxH motif in the stability, structure, and function of AR proteins by a systematic and rationalized mutagenic study on, followed by biochemical and biophysical characterization of, gankyrin, an oncogenic protein composed of seven ARs and six T/SxxH tetrapeptides, and P16, a tumor suppressor with four ARs but no TPLH tetrapeptide. Our results showed that this tetrapeptide is ineffectual on global structure and function, but contributes significantly to conformational stability when its stabilizing potentials are fully realized in the local conformation, including (1) the intra-AR hydrogen bonding involving the hydroxyl group; (2) the intra-AR and inter-AR hydrogen bonds involving the imidazole ring; and (3) the hydrophobic interaction associated with the Thr-methyl group. Considering that the capping and close-to-capping units tend to have more sequence diversity and more conformational variation, it could be also generally true that a T/SxxH motif close to the terminal repeats contributes little or even negatively to stability with respect to Ala substitution, but substantially stabilizes the global conformation when located in the middle of a long stretch of ARs.
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Affiliation(s)
- Yi Guo
- Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA
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