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Azadmanesh J, Slobodnik K, Struble LR, Cone EA, Dasgupta M, Lutz WE, Kumar S, Natarajan A, Coates L, Weiss KL, Myles DAA, Kroll T, Borgstahl GEO. The role of Tyr34 in proton-coupled electron transfer of human manganese superoxide dismutase. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.29.596464. [PMID: 38853997 PMCID: PMC11160768 DOI: 10.1101/2024.05.29.596464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
Human manganese superoxide dismutase (MnSOD) plays a crucial role in controlling levels of reactive oxygen species (ROS) by converting superoxide (O 2 •- ) to molecular oxygen (O 2 ) and hydrogen peroxide (H 2 O 2 ) with proton-coupled electron transfers (PCETs). The reactivity of human MnSOD is determined by the state of a key catalytic residue, Tyr34, that becomes post-translationally inactivated by nitration in various diseases associated with mitochondrial dysfunction. We previously reported that Tyr34 has an unusual pK a due to its proximity to the Mn metal and undergoes cyclic deprotonation and protonation events to promote the electron transfers of MnSOD. To shed light on the role of Tyr34 MnSOD catalysis, we performed neutron diffraction, X-ray spectroscopy, and quantum chemistry calculations of Tyr34Phe MnSOD in various enzymatic states. The data identifies the contributions of Tyr34 in MnSOD activity that support mitochondrial function and presents a thorough characterization of how a single tyrosine modulates PCET catalysis.
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2
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Borgstahl G, Azadmanesh J, Slobodnik K, Struble L, Lutz W, Coates L, Weiss K, Myles D, Kroll T. Revealing the atomic and electronic mechanism of human manganese superoxide dismutase product inhibition. RESEARCH SQUARE 2024:rs.3.rs-3880128. [PMID: 38405788 PMCID: PMC10889052 DOI: 10.21203/rs.3.rs-3880128/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Human manganese superoxide dismutase (MnSOD) is a crucial oxidoreductase that maintains the vitality of mitochondria by converting O 2 ∙ - to O 2 and H 2 O 2 with proton-coupled electron transfers (PCETs). Since changes in mitochondrial H 2 O 2 concentrations are capable of stimulating apoptotic signaling pathways, human MnSOD has evolutionarily gained the ability to be highly inhibited by its own product, H 2 O 2 . A separate set of PCETs is thought to regulate product inhibition, though mechanisms of PCETs are typically unknown due to difficulties in detecting the protonation states of specific residues that coincide with the electronic state of the redox center. To shed light on the underlying mechanism, we combined neutron diffraction and X-ray absorption spectroscopy of the product-bound, trivalent, and divalent states to reveal the all-atom structures and electronic configuration of the metal. The data identifies the product-inhibited complex for the first time and a PCET mechanism of inhibition is constructed.
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3
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Azadmanesh J, Slobodnik K, Struble LR, Lutz WE, Coates L, Weiss KL, Myles DAA, Kroll T, Borgstahl GEO. Revealing the atomic and electronic mechanism of human manganese superoxide dismutase product inhibition. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.26.577433. [PMID: 38328249 PMCID: PMC10849630 DOI: 10.1101/2024.01.26.577433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
Human manganese superoxide dismutase (MnSOD) is a crucial oxidoreductase that maintains the vitality of mitochondria by converting O 2 ●- to O 2 and H 2 O 2 with proton-coupled electron transfers (PCETs). Since changes in mitochondrial H 2 O 2 concentrations are capable of stimulating apoptotic signaling pathways, human MnSOD has evolutionarily gained the ability to be highly inhibited by its own product, H 2 O 2 . A separate set of PCETs is thought to regulate product inhibition, though mechanisms of PCETs are typically unknown due to difficulties in detecting the protonation states of specific residues that coincide with the electronic state of the redox center. To shed light on the underlying mechanism, we combined neutron diffraction and X-ray absorption spectroscopy of the product-bound, trivalent, and divalent states to reveal the all-atom structures and electronic configuration of the metal. The data identifies the product-inhibited complex for the first time and a PCET mechanism of inhibition is constructed.
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4
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Llopiz A, Ramírez-Martínez MA, Olvera L, Xolalpa-Villanueva W, Pastor N, Saab-Rincon G. The Role of a Loop in the Non-catalytic Domain B on the Hydrolysis/Transglycosylation Specificity of the 4-α-Glucanotransferase from Thermotoga maritima. Protein J 2023; 42:502-518. [PMID: 37464145 PMCID: PMC10480278 DOI: 10.1007/s10930-023-10136-2] [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] [Accepted: 06/27/2023] [Indexed: 07/20/2023]
Abstract
The mechanism by which glycoside hydrolases control the reaction specificity through hydrolysis or transglycosylation is a key element embedded in their chemical structures. The determinants of reaction specificity seem to be complex. We looked for structural differences in domain B between the 4-α-glucanotransferase from Thermotoga maritima (TmGTase) and the α-amylase from Thermotoga petrophila (TpAmylase) and found a longer loop in the former that extends towards the active site carrying a W residue at its tip. Based on these differences we constructed the variants W131G and the partial deletion of the loop at residues 120-124/128-131, which showed a 11.6 and 11.4-fold increased hydrolysis/transglycosylation (H/T) ratio relative to WT protein, respectively. These variants had a reduction in the maximum velocity of the transglycosylation reaction, while their affinity for maltose as the acceptor was not substantially affected. Molecular dynamics simulations allow us to rationalize the increase in H/T ratio in terms of the flexibility near the active site and the conformations of the catalytic acid residues and their associated pKas.
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Affiliation(s)
- Alexey Llopiz
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, 62209, Cuernavaca, Morelos, Mexico
| | - Marco A Ramírez-Martínez
- Centro de Investigación en Dinámica Celular, IICBA, Universidad Autónoma del Estado de Morelos, 62209, Cuernavaca, Morelos, Mexico
| | - Leticia Olvera
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, 62209, Cuernavaca, Morelos, Mexico
| | - Wendy Xolalpa-Villanueva
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, 62209, Cuernavaca, Morelos, Mexico
| | - Nina Pastor
- Centro de Investigación en Dinámica Celular, IICBA, Universidad Autónoma del Estado de Morelos, 62209, Cuernavaca, Morelos, Mexico
| | - Gloria Saab-Rincon
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, 62209, Cuernavaca, Morelos, Mexico.
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5
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Walton-Raaby M, Floen T, García-Díez G, Mora-Diez N. Calculating the Aqueous pK a of Phenols: Predictions for Antioxidants and Cannabinoids. Antioxidants (Basel) 2023; 12:1420. [PMID: 37507958 PMCID: PMC10376140 DOI: 10.3390/antiox12071420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 06/30/2023] [Accepted: 07/10/2023] [Indexed: 07/30/2023] Open
Abstract
We aim to develop a theoretical methodology for the accurate aqueous pKa prediction of structurally complex phenolic antioxidants and cannabinoids. In this study, five functionals (M06-2X, B3LYP, BHandHLYP, PBE0, and TPSS) and two solvent models (SMD and PCM) were combined with the 6-311++G(d,p) basis set to predict pKa values for twenty structurally simple phenols. None of the direct calculations produced good results. However, the correlations between the calculated Gibbs energy difference of each acid and its conjugate base, ΔGaq(BA)°=ΔGaqA-°-ΔGaq(HA)°, and the experimental aqueous pKa values had superior predictive accuracy, which was also tested relative to an independent set of ten molecules of which six were structurally complex phenols. New correlations were built with twenty-seven phenols (including the phenols with experimental pKa values from the test set), which were used to make predictions. The best correlation equations used the PCM method and produced mean absolute errors of 0.26-0.27 pKa units and R2 values of 0.957-0.960. The average range of predictions for the potential antioxidants (cannabinoids) was 0.15 (0.25) pKa units, which indicates good agreement between our methodologies. The new correlation equations could be used to make pKa predictions for other phenols in water and potentially in other solvents where they might be more soluble.
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Affiliation(s)
- Max Walton-Raaby
- Department of Chemistry, Thompson Rivers University, Kamloops, BC V2C 0C8, Canada
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Tyler Floen
- Department of Chemistry, Thompson Rivers University, Kamloops, BC V2C 0C8, Canada
| | | | - Nelaine Mora-Diez
- Department of Chemistry, Thompson Rivers University, Kamloops, BC V2C 0C8, Canada
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6
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Hou J, Lei X, Liu B, Wang Z, Fang G, Liu J, Wang S. A study on the catalytic activity of polypeptides toward the hydrolysis of glucoside compounds gastrodin, polydatin and esculin. J Mater Chem B 2022; 10:9878-9886. [PMID: 36437799 DOI: 10.1039/d2tb01758j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The self-assembly of a series of catalytically active polypeptides toward hydrolysis of glucoside compounds, namely, gastrodin, polydatin and esculin was investigated. These active peptides are composed of two functional fragments: one is the hydrophobic sequence LHLHLRL, which forms assembling segments in the presence of Zn ions (Zn2+); another functional sequence of active peptides are catalytic sites such as Glu (E), Asp (D) and His (H), where carboxylic acids (-COOH) or imidazole groups act like scissors to cleave glucoside bonds of the compounds (according to the acid-base coupling mechanism). The effects of the amino acid sequence of the peptide, Zn2+ concentration, pH and the size or steric hindrance of glucoside compounds on the hydrolytic activity were studied. It was found that the crystalline structure of assembled peptides was crucial to provide the peptide with catalytic hydrolytic activity. Noncovalent interaction index was used to analyse the noncovalent interaction of PEs with glucoside compounds, including hydrogen bonds, van der Waals, and steric effect in the complexes. The binding energy of complexes, the direction and site of nucleophilic attack during deglycosylation processes were also investigated by molecular docking and the electron density Laplace function. This revealed that the differences in the hydrolytic activity of peptides toward glucoside compounds with different sizes originated from different hydrogen bond interactions between the peptides and substrates. These active peptides may find application in the preparation of drugs by de-glycosylation of natural compounds.
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Affiliation(s)
- Juan Hou
- State Key Laboratory of Food Nutrition and Safety, Key Laboratory of Food Quality and Healthy of Tianjin, College of Food Science and Engineering, Tianjin University of Science and Technology, Tianjin, 300457, P. R. China.
| | - Xiangmin Lei
- State Key Laboratory of Food Nutrition and Safety, Key Laboratory of Food Quality and Healthy of Tianjin, College of Food Science and Engineering, Tianjin University of Science and Technology, Tianjin, 300457, P. R. China.
| | - Borui Liu
- College of Chemistry, Jilin University, Changchun, 130012, China
| | - Zejiang Wang
- State Key Laboratory of Food Nutrition and Safety, Key Laboratory of Food Quality and Healthy of Tianjin, College of Food Science and Engineering, Tianjin University of Science and Technology, Tianjin, 300457, P. R. China.
| | - Guozhen Fang
- State Key Laboratory of Food Nutrition and Safety, Key Laboratory of Food Quality and Healthy of Tianjin, College of Food Science and Engineering, Tianjin University of Science and Technology, Tianjin, 300457, P. R. China.
| | - Jifeng Liu
- State Key Laboratory of Food Nutrition and Safety, Key Laboratory of Food Quality and Healthy of Tianjin, College of Food Science and Engineering, Tianjin University of Science and Technology, Tianjin, 300457, P. R. China.
| | - Shuo Wang
- State Key Laboratory of Food Nutrition and Safety, Key Laboratory of Food Quality and Healthy of Tianjin, College of Food Science and Engineering, Tianjin University of Science and Technology, Tianjin, 300457, P. R. China. .,Research Center of Food Science and Human Health, School of Medicine, Nankai University, Tianjin, 300071, P. R. China
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7
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Lyu Y, Scrimin P. Mimicking Enzymes: The Quest for Powerful Catalysts from Simple Molecules to Nanozymes. ACS Catal 2021. [DOI: 10.1021/acscatal.1c01219] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Yanchao Lyu
- University of Padova, Department of Chemical Sciences, via Marzolo, 1, 35131 Padova, Italy
| | - Paolo Scrimin
- University of Padova, Department of Chemical Sciences, via Marzolo, 1, 35131 Padova, Italy
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8
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Dhakad A, Jena S, Sahoo DK, Biswal HS. Quantification of the electric field inside protein active sites and fullerenes. Phys Chem Chem Phys 2021; 23:14755-14763. [PMID: 34195713 DOI: 10.1039/d1cp01769a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
While electrostatic interactions are exceedingly accountable for biological functions, no simple method exists to directly estimate or measure the electrostatic field in protein active sites. The electrostatic field inside the protein is generally inferred from the shift in the vibrational stretching frequencies of nitrile and thionitrile probes at the active sites through several painstaking and time-consuming experiments like vibrational Stark effect spectroscopy (VSS). Here we present a simple, fast, and reliable methodology, which can efficiently predict the vibrational Stark tuning rates (VSRs) of a large variety of probes within 10% error of the reported experimental data. Our methodology is based on geometry optimization and frequency calculations in the presence of an external electric field to predict the accurate VSR of newly designed nitrile/thionitrile probes. A priori information of VSRs is useful for difficult experiments such as catalytic/enzymatic study and in structural biology. We also applied our methodology successfully to estimate the electric field inside fullerenes and nano-onions, which is encouraging for researchers to adopt it for further applications in materials science and supramolecular chemistry.
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Affiliation(s)
- Ambuj Dhakad
- School of Chemical Sciences, National Institute of Science Education and Research (NISER) PO- Bhimpur-Padanpur, Via-Jatni, District- Khurda, PIN - 752050, Bhubaneswar, India. and Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094, India
| | - Subhrakant Jena
- School of Chemical Sciences, National Institute of Science Education and Research (NISER) PO- Bhimpur-Padanpur, Via-Jatni, District- Khurda, PIN - 752050, Bhubaneswar, India. and Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094, India
| | - Dipak Kumar Sahoo
- School of Chemical Sciences, National Institute of Science Education and Research (NISER) PO- Bhimpur-Padanpur, Via-Jatni, District- Khurda, PIN - 752050, Bhubaneswar, India. and Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094, India
| | - Himansu S Biswal
- School of Chemical Sciences, National Institute of Science Education and Research (NISER) PO- Bhimpur-Padanpur, Via-Jatni, District- Khurda, PIN - 752050, Bhubaneswar, India. and Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094, India
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9
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Gupta PL, Smith JS, Roitberg AE. pH Effects and Cooperativity among Key Titratable Residues for Escherichia coli Glycinamide Ribonucleotide Transformylase. J Phys Chem B 2021; 125:9168-9185. [PMID: 34351775 DOI: 10.1021/acs.jpcb.1c04668] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Human glycinamide ribonucleotide transformylase (GAR Tfase) is a regulatory enzyme in the de novo purine biosynthesis pathway that has been extensively studied as an anticancer target. To some extent, inhibition of GAR Tfase selectively targets cancer cells over normal cells and inhibits purine formation and DNA replication. In this study, we investigated E. coli GAR Tfase, which shares high sequence similarity with the human GAR Tfase, and most functional residues are conserved. Herein, we aim to predict the pH-activity curve through a computational approach. We carried out pH-replica exchange molecular dynamics (pH-REMD) simulations to investigate pH-dependent functions such as structural changes, ligand binding, and catalytic activity. To compute the pH-activity curve, we identified the catalytic residues in specific protonation states, referred to as the catalytic competent protonation states (CCPS), which maintain the structure, keep ligands bound, and facilitate catalysis. Our computed population of CCPS with respect to pH matches well with the experimental pH-activity curve. To compute the microscopic pKa values in the catalytically active conformation, we devised a thermodynamic model that considers the coupling between protonation states of CCPS residues and conformational states. These results allow us to correctly identify the general acid and base catalysts and interpret the pH-activity curve at an atomistic level.
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Affiliation(s)
- Pancham Lal Gupta
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611-7200, United States
| | - Justin S Smith
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Adrian E Roitberg
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611-7200, United States
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10
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Kaira GS, Kapoor M. Molecular advancements on over-expression, stability and catalytic aspects of endo-β-mannanases. Crit Rev Biotechnol 2020; 41:1-15. [PMID: 33032458 DOI: 10.1080/07388551.2020.1825320] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The hydrolysis of mannans by endo-β-mannanases continues to gather significance as exemplified by its commercial applications in food, feed, and a rekindled interest in biorefineries. The present review provides a comprehensive account of fundamental research and fascinating insights in the field of endo-β-mannanase engineering in order to improve over-expression and to decipher molecular determinants governing activity-stability during harsh conditions, substrate recognition, polysaccharide specificity, endo/exo mode of action and multi-functional activities in the modular polypeptide. In-depth analysis of the available literature has also been made on rational and directed evolution approaches, which have translated native endo-β-mannanases into superior biocatalysts for satisfying industrial requirements.
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Affiliation(s)
- Gaurav Singh Kaira
- Department of Protein Chemistry and Technology, CSIR-Central Food Technological Research Institute, Mysuru, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
| | - Mukesh Kapoor
- Department of Protein Chemistry and Technology, CSIR-Central Food Technological Research Institute, Mysuru, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
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11
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Zhao R, Wang M, Chen J, Tong Y, Wei GW. The de Rham-Hodge Analysis and Modeling of Biomolecules. Bull Math Biol 2020; 82:108. [PMID: 32770408 PMCID: PMC8137271 DOI: 10.1007/s11538-020-00783-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2019] [Accepted: 07/20/2020] [Indexed: 12/18/2022]
Abstract
Biological macromolecules have intricate structures that underpin their biological functions. Understanding their structure-function relationships remains a challenge due to their structural complexity and functional variability. Although de Rham-Hodge theory, a landmark of twentieth-century mathematics, has had a tremendous impact on mathematics and physics, it has not been devised for macromolecular modeling and analysis. In this work, we introduce de Rham-Hodge theory as a unified paradigm for analyzing the geometry, topology, flexibility, and Hodge mode analysis of biological macromolecules. Geometric characteristics and topological invariants are obtained either from the Helmholtz-Hodge decomposition of the scalar, vector, and/or tensor fields of a macromolecule or from the spectral analysis of various Laplace-de Rham operators defined on the molecular manifolds. We propose Laplace-de Rham spectral-based models for predicting macromolecular flexibility. We further construct a Laplace-de Rham-Helfrich operator for revealing cryo-EM natural frequencies. Extensive experiments are carried out to demonstrate that the proposed de Rham-Hodge paradigm is one of the most versatile tools for the multiscale modeling and analysis of biological macromolecules and subcellular organelles. Accurate, reliable, and topological structure-preserving algorithms for implementing discrete exterior calculus (DEC) have been developed to facilitate the aforementioned modeling and analysis of biological macromolecules. The proposed de Rham-Hodge paradigm has potential applications to subcellular organelles and the structure construction from medium- or low-resolution cryo-EM maps, and functional predictions from massive biomolecular datasets.
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Affiliation(s)
- Rundong Zhao
- Department of Computer Science and Engineering, Michigan State University, East Lansing, MI, 48824, USA
| | - Menglun Wang
- Department of Mathematics, Michigan State University, East Lansing, MI, 48824, USA
| | - Jiahui Chen
- Department of Mathematics, Michigan State University, East Lansing, MI, 48824, USA
| | - Yiying Tong
- Department of Computer Science and Engineering, Michigan State University, East Lansing, MI, 48824, USA.
| | - Guo-Wei Wei
- Department of Mathematics, Michigan State University, East Lansing, MI, 48824, USA.
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI, 48824, USA.
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA.
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12
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Bandyopadhyay D, Bhatnagar A, Jain S, Pratyaksh P. Selective Stabilization of Aspartic Acid Protonation State within a Given Protein Conformation Occurs via Specific "Molecular Association". J Phys Chem B 2020; 124:5350-5361. [PMID: 32484348 DOI: 10.1021/acs.jpcb.0c02629] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Proteins involved in proton-/electron-transfer processes often possess "functional" aspartates/aspartic acids (Asp) with variable protonation states. The mechanism of Asp protonation-deprotonation within proteins is unclear. Two questions were asked-the possible types of determinants responsible for Asp protonation-deprotonation and the spatial arrangements of the determinants leading to selective stabilization. The questions were analyzed using nine different solvent models, which scanned the complete protein dielectric range, and four protein models, which illustrated the spatial arrangements around Asp, termed as "molecular association". The methods employed were quantum chemical calculations and constant pH simulations. The types of the determinants identified were charge-charge interaction, H bonding, dipole-π interaction, extended electronic conjugation, dielectric effect, and solvent accessibility. All solvent-exposed Asp [buried fraction (BF) less than 0.5] were aspartates, and buried Asp were either aspartic acids or aspartates, each having a different "molecular association". The exposed aspartates were stabilized via a H-bonding network with bulk water, buried aspartates via salt bridge or, minimum, two intramolecular H bonds, and buried aspartic acids via, minimum, one intramolecular H bond. An "acid-alcohol pair" (involving Ser/Thr/Tyr) was a common determinant to any "functional" buried aspartate/aspartic acid. Higher energy "molecular associations" observed within proteins compared to those within water, presumably, indicated easy molecular restructuring and alteration of the Asp protonation states during a protein-mediated proton/electron transfer.
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Affiliation(s)
- Debashree Bandyopadhyay
- Department of Biological Sciences, Birla Institute of Technology and Science, Pilani, Hyderabad campus, Hyderabad 500078, India
| | - Akshay Bhatnagar
- Department of Biological Sciences, Birla Institute of Technology and Science, Pilani, Hyderabad campus, Hyderabad 500078, India
| | - Shobhit Jain
- Department of Biological Sciences, Birla Institute of Technology and Science, Pilani, Hyderabad campus, Hyderabad 500078, India
| | - Prabhav Pratyaksh
- Department of Biological Sciences, Birla Institute of Technology and Science, Pilani, Hyderabad campus, Hyderabad 500078, India
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13
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Sandoval-Lira J, Mondragón-Solórzano G, Lugo-Fuentes LI, Barroso-Flores J. Accurate Estimation of p Kb Values for Amino Groups from Surface Electrostatic Potential ( VS,min) Calculations: The Isoelectric Points of Amino Acids as a Case Study. J Chem Inf Model 2020; 60:1445-1452. [PMID: 32108480 DOI: 10.1021/acs.jcim.9b01173] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Theoretical calculation of equilibrium dissociation constants is a very computationally demanding and time-consuming process since it requires an extremely accurate computation of the solvation free energy changes for each of the species involved. By correlating the minimum surface electrostatic potential (VS,min) on the nitrogen atom of several aliphatic amino groups-calculated at the density functional theory (DFT) ωB97X-D/cc-pVDZ level of theory-we obtained regression models for each kind of substitution pattern from which we interpolate their corresponding pKb values with remarkable accuracy: primary R2 = 0.9519; secondary R2 = 0.9112; and tertiary R2 = 0.8172 (N = 20 for each family). These models were validated with tests sets (N = 5) with mean absolute error (MAE) values of 0.1213 (primary), 0.4407 (secondary), and 0.3057 (tertiary). Combining this ansatz with another previously reported by our group to estimate pKa values [Caballero-García, G.; et al. Molecules 2019, 24(1), 79] we are able to reproduce the isoelectric points of 13 amino acids with no titrable side chains with MAE = 0.4636 pI units.
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Affiliation(s)
- Jacinto Sandoval-Lira
- Centro Conjunto de Investigación en Quı́mica Sustentable UAEM-UNAM, Carretera Toluca-Atlacomulco Km. 14.5, Unidad San Cayetano, Toluca de Lerdo 50200, México.,Instituto de Quı́mica, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, CDMX 04510, México
| | - Gustavo Mondragón-Solórzano
- Centro Conjunto de Investigación en Quı́mica Sustentable UAEM-UNAM, Carretera Toluca-Atlacomulco Km. 14.5, Unidad San Cayetano, Toluca de Lerdo 50200, México.,Instituto de Quı́mica, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, CDMX 04510, México
| | - Leonardo I Lugo-Fuentes
- Departamento de Quı́mica, División de Ciencias Naturales y Exactas, Universidad de Guanajuato, Noria Alta S/N, Guanajuato 36050, México
| | - Joaquín Barroso-Flores
- Centro Conjunto de Investigación en Quı́mica Sustentable UAEM-UNAM, Carretera Toluca-Atlacomulco Km. 14.5, Unidad San Cayetano, Toluca de Lerdo 50200, México.,Instituto de Quı́mica, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, CDMX 04510, México
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14
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Davis TD, Michaud JM, Burkart MD. Active site labeling of fatty acid and polyketide acyl-carrier protein transacylases. Org Biomol Chem 2020; 17:4720-4724. [PMID: 31044196 DOI: 10.1039/c8ob03229g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Metabolic engineering of fatty acids and polyketides remains challenging due to unresolved protein-protein interactions that are essential to synthase activity. While several chemical probes have been developed to capture and visualize protein interfaces in these systems, acyl carrier protein (ACP) transacylase (AT) domains remain elusive. Herein, we combine a mutational strategy with fluorescent probe design to expedite the study of AT domains from fatty acid and polyketide synthases. We describe the design and evaluation of inhibitor-inspired and substrate-mimetic reporters containing sulfonyl fluoride and β-lactone warheads. Moreover, specific active-site labeling occurs by optimizing pH, time, and probe concentration, and selective labeling is achieved in the presence of inhibitors of competing domains. These findings provide a panel of AT-targeting probes and set the stage for future combinatorial biosynthetic and drug discovery initiatives.
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Affiliation(s)
- Tony D Davis
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0358, USA.
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15
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Damis SIR, Murad AMA, Diba Abu Bakar F, Rashid SA, Jaafar NR, Illias RM. Protein engineering of GH11 xylanase from Aspergillus fumigatus RT-1 for catalytic efficiency improvement on kenaf biomass hydrolysis. Enzyme Microb Technol 2019; 131:109383. [DOI: 10.1016/j.enzmictec.2019.109383] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Revised: 06/30/2019] [Accepted: 07/16/2019] [Indexed: 11/15/2022]
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16
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Muttathukattil AN, Srinivasan S, Halder A, Reddy G. Role of Guanidinium-Carboxylate Ion Interaction in Enzyme Inhibition with Implications for Drug Design. J Phys Chem B 2019; 123:9302-9311. [DOI: 10.1021/acs.jpcb.9b06130] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Aswathy N. Muttathukattil
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Sriraksha Srinivasan
- Department of Chemistry, St. Joseph’s College, Bangalore, Karnataka 560027, India
| | - Antarip Halder
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Govardhan Reddy
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, Karnataka 560012, India
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17
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Challenges and Adaptations of Life in Alkaline Habitats. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2019; 172:85-133. [DOI: 10.1007/10_2019_97] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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18
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Biochemical and functional characterization of a novel thermoacidophilic, heat and halo-ionic liquids tolerant endo-β-1,4-glucanase from saline-alkaline lake soil microbial metagenomic DNA. Int J Biol Macromol 2018; 118:1035-1044. [DOI: 10.1016/j.ijbiomac.2018.06.141] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 06/26/2018] [Accepted: 06/26/2018] [Indexed: 11/21/2022]
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19
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Slocum JD, Webb LJ. Measuring Electric Fields in Biological Matter Using the Vibrational Stark Effect of Nitrile Probes. Annu Rev Phys Chem 2018; 69:253-271. [DOI: 10.1146/annurev-physchem-052516-045011] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Joshua D. Slocum
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712-1224, USA
| | - Lauren J. Webb
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712-1224, USA
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20
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Huang Y, Yue Z, Tsai CC, Henderson JA, Shen J. Predicting Catalytic Proton Donors and Nucleophiles in Enzymes: How Adding Dynamics Helps Elucidate the Structure-Function Relationships. J Phys Chem Lett 2018; 9:1179-1184. [PMID: 29461836 PMCID: PMC6555141 DOI: 10.1021/acs.jpclett.8b00238] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Despite the relevance of understanding structure-function relationships, robust prediction of proton donors and nucleophiles in enzyme active sites remains challenging. Here we tested three types of state-of-the-art computational methods to calculate the p Ka's of the buried and hydrogen bonded catalytic dyads in five enzymes. We asked the question what determines the p Ka order, i.e., what makes a residue proton donor vs a nucleophile. The continuous constant pH molecular dynamics simulations captured the experimental p Ka orders and revealed that the negative nucleophile is stabilized by increased hydrogen bonding and solvent exposure as compared to the proton donor. Surprisingly, this simple trend is not apparent from crystal structures and the static structure-based calculations. While the generality of the findings awaits further testing via a larger set of data, they underscore the role of dynamics in bridging enzyme structures and functions.
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Affiliation(s)
- Yandong Huang
- Department of Pharmaceutical Sciences , University of Maryland School of Pharmacy , Baltimore , Maryland 21201 , United States
| | - Zhi Yue
- Department of Pharmaceutical Sciences , University of Maryland School of Pharmacy , Baltimore , Maryland 21201 , United States
| | - Cheng-Chieh Tsai
- Department of Pharmaceutical Sciences , University of Maryland School of Pharmacy , Baltimore , Maryland 21201 , United States
| | - Jack A Henderson
- Department of Pharmaceutical Sciences , University of Maryland School of Pharmacy , Baltimore , Maryland 21201 , United States
| | - Jana Shen
- Department of Pharmaceutical Sciences , University of Maryland School of Pharmacy , Baltimore , Maryland 21201 , United States
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21
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Azadmanesh J, Borgstahl GEO. A Review of the Catalytic Mechanism of Human Manganese Superoxide Dismutase. Antioxidants (Basel) 2018; 7:antiox7020025. [PMID: 29385710 PMCID: PMC5836015 DOI: 10.3390/antiox7020025] [Citation(s) in RCA: 100] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2017] [Revised: 01/13/2018] [Accepted: 01/26/2018] [Indexed: 12/15/2022] Open
Abstract
Superoxide dismutases (SODs) are necessary antioxidant enzymes that protect cells from reactive oxygen species (ROS). Decreased levels of SODs or mutations that affect their catalytic activity have serious phenotypic consequences. SODs perform their bio-protective role by converting superoxide into oxygen and hydrogen peroxide by cyclic oxidation and reduction reactions with the active site metal. Mutations of SODs can cause cancer of the lung, colon, and lymphatic system, as well as neurodegenerative diseases such as Parkinson's disease and amyotrophic lateral sclerosis. While SODs have proven to be of significant biological importance since their discovery in 1968, the mechanistic nature of their catalytic function remains elusive. Extensive investigations with a multitude of approaches have tried to unveil the catalytic workings of SODs, but experimental limitations have impeded direct observations of the mechanism. Here, we focus on human MnSOD, the most significant enzyme in protecting against ROS in the human body. Human MnSOD resides in the mitochondrial matrix, the location of up to 90% of cellular ROS generation. We review the current knowledge of the MnSOD enzymatic mechanism and ongoing studies into solving the remaining mysteries.
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Affiliation(s)
- Jahaun Azadmanesh
- Department of Biochemistry and Molecular Biology, 985870 Nebraska Medical Center, Omaha, NE 68198-5870, USA.
| | - Gloria E O Borgstahl
- Department of Biochemistry and Molecular Biology, 985870 Nebraska Medical Center, Omaha, NE 68198-5870, USA.
- Eppley Institute for Cancer and Allied Diseases, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, USA.
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22
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Morris DL, Leeper TC, Ziegler CJ. Inhibition of lysozyme's polymerization activity using a polymer structural mimic. Polym Chem 2018. [DOI: 10.1039/c8py00545a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hen egg white lysozyme (HEWL) is a green catalyst capable of polymerizing the formation of 2-ethynylpyridine. 1,3-di(2-pyridyl)propane (DPP) is a mimic of the polymer repeating unit and a polymerization inhibitor. DPP's interaction with HEWL reveals structural insight into the mechanism of polymerization.
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Affiliation(s)
- D. L. Morris
- The University of Akron 302 E Buchtel Ave
- Akron
- USA
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23
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Wu H, Tian X, Dong Z, Zhang Y, Huang L, Liu X, Jin P, Lu F, Wang Z. Engineering of Bacillus amyloliquefaciens
α-Amylase with Improved Calcium Independence and Catalytic Efficiency by Error-Prone PCR. STARCH-STARKE 2017. [DOI: 10.1002/star.201700175] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Haiyang Wu
- H. Wu, X. Tian, Dr. Z. Dong, Prof. X. Liu, Dr. P. Jin, Prof. Z. Wang; Department of Biological Chemical Engineering; College of Chemical Engineering and Materials Science; Tianjin University of Science and Technology; Tianjin 300457 China
- H. Wu, X. Tian, Y. Zhang, L. Huang, Prof. F. Lu, Prof. Z. Wang; College of Biotechnology; Tianjin University of Science and Technology; Tianjin 300457 China
| | - Xiaojing Tian
- H. Wu, X. Tian, Dr. Z. Dong, Prof. X. Liu, Dr. P. Jin, Prof. Z. Wang; Department of Biological Chemical Engineering; College of Chemical Engineering and Materials Science; Tianjin University of Science and Technology; Tianjin 300457 China
- H. Wu, X. Tian, Y. Zhang, L. Huang, Prof. F. Lu, Prof. Z. Wang; College of Biotechnology; Tianjin University of Science and Technology; Tianjin 300457 China
| | - Zixing Dong
- H. Wu, X. Tian, Dr. Z. Dong, Prof. X. Liu, Dr. P. Jin, Prof. Z. Wang; Department of Biological Chemical Engineering; College of Chemical Engineering and Materials Science; Tianjin University of Science and Technology; Tianjin 300457 China
| | - Yongjie Zhang
- H. Wu, X. Tian, Y. Zhang, L. Huang, Prof. F. Lu, Prof. Z. Wang; College of Biotechnology; Tianjin University of Science and Technology; Tianjin 300457 China
| | - Lei Huang
- H. Wu, X. Tian, Y. Zhang, L. Huang, Prof. F. Lu, Prof. Z. Wang; College of Biotechnology; Tianjin University of Science and Technology; Tianjin 300457 China
| | - Xiaoguang Liu
- H. Wu, X. Tian, Dr. Z. Dong, Prof. X. Liu, Dr. P. Jin, Prof. Z. Wang; Department of Biological Chemical Engineering; College of Chemical Engineering and Materials Science; Tianjin University of Science and Technology; Tianjin 300457 China
| | - Peng Jin
- H. Wu, X. Tian, Dr. Z. Dong, Prof. X. Liu, Dr. P. Jin, Prof. Z. Wang; Department of Biological Chemical Engineering; College of Chemical Engineering and Materials Science; Tianjin University of Science and Technology; Tianjin 300457 China
| | - Fuping Lu
- H. Wu, X. Tian, Y. Zhang, L. Huang, Prof. F. Lu, Prof. Z. Wang; College of Biotechnology; Tianjin University of Science and Technology; Tianjin 300457 China
| | - Zhengxiang Wang
- H. Wu, X. Tian, Dr. Z. Dong, Prof. X. Liu, Dr. P. Jin, Prof. Z. Wang; Department of Biological Chemical Engineering; College of Chemical Engineering and Materials Science; Tianjin University of Science and Technology; Tianjin 300457 China
- H. Wu, X. Tian, Y. Zhang, L. Huang, Prof. F. Lu, Prof. Z. Wang; College of Biotechnology; Tianjin University of Science and Technology; Tianjin 300457 China
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24
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Ronchi VP, Kim ED, Summa CM, Klein JM, Haas AL. In silico modeling of the cryptic E2∼ubiquitin-binding site of E6-associated protein (E6AP)/UBE3A reveals the mechanism of polyubiquitin chain assembly. J Biol Chem 2017; 292:18006-18023. [PMID: 28924046 DOI: 10.1074/jbc.m117.813477] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Indexed: 12/13/2022] Open
Abstract
To understand the mechanism for assembly of Lys48-linked polyubiquitin degradation signals, we previously demonstrated that the E6AP/UBE3A ligase harbors two functionally distinct E2∼ubiquitin-binding sites: a high-affinity Site 1 required for E6AP Cys820∼ubiquitin thioester formation and a canonical Site 2 responsible for subsequent chain elongation. Ordered binding to Sites 1 and 2 is here revealed by observation of UbcH7∼ubiquitin-dependent substrate inhibition of chain formation at micromolar concentrations. To understand substrate inhibition, we exploited the PatchDock algorithm to model in silico UbcH7∼ubiquitin bound to Site 1, validated by chain assembly kinetics of selected point mutants. The predicted structure buries an extensive solvent-excluded surface bringing the UbcH7∼ubiquitin thioester bond within 6 Å of the Cys820 nucleophile. Modeling onto the active E6AP trimer suggests that substrate inhibition arises from steric hindrance between Sites 1 and 2 of adjacent subunits. Confirmation that Sites 1 and 2 function in trans was demonstrated by examining the effect of E6APC820A on wild-type activity and single-turnover pulse-chase kinetics. A cyclic proximal indexation model proposes that Sites 1 and 2 function in tandem to assemble thioester-linked polyubiquitin chains from the proximal end attached to Cys820 before stochastic en bloc transfer to the target protein. Non-reducing SDS-PAGE confirms assembly of the predicted Cys820-linked 125I-polyubiquitin thioester intermediate. Other studies suggest that Glu550 serves as a general base to generate the Cys820 thiolate within the low dielectric binding interface and Arg506 functions to orient Glu550 and to stabilize the incipient anionic transition state during thioester exchange.
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Affiliation(s)
| | - Elizabeth D Kim
- From the Department of Biochemistry and Molecular Biology and
| | - Christopher M Summa
- the Department of Computer Science, University of New Orleans, New Orleans, Louisiana 70148
| | | | - Arthur L Haas
- From the Department of Biochemistry and Molecular Biology and .,the Stanley S. Scott Cancer Center, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112 and
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25
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26
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Meekrathok P, Kukic P, Nielsen JE, Suginta W. Investigation of Ionization Pattern of the Adjacent Acidic Residues in the DXDXE Motif of GH-18 Chitinases Using Theoretical pKa Calculations. J Chem Inf Model 2017; 57:572-583. [DOI: 10.1021/acs.jcim.6b00536] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Piyanat Meekrathok
- Biochemistry-Electrochemistry
Research Group and School of Chemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
| | - Predrag Kukic
- School
of Biomolecular and Biomedical Science, University College Dublin, Belfield, Dublin 4, Ireland
| | - Jens Erik Nielsen
- School
of Biomolecular and Biomedical Science, University College Dublin, Belfield, Dublin 4, Ireland
| | - Wipa Suginta
- Biochemistry-Electrochemistry
Research Group and School of Chemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
- Centre
of Excellence in Advanced Functional Materials, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
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27
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Arthur EJ, Brooks CL. Efficient implementation of constant pH molecular dynamics on modern graphics processors. J Comput Chem 2016; 37:2171-80. [PMID: 27405884 DOI: 10.1002/jcc.24435] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 06/02/2016] [Accepted: 06/03/2016] [Indexed: 12/15/2022]
Abstract
The treatment of pH sensitive ionization states for titratable residues in proteins is often omitted from molecular dynamics (MD) simulations. While static charge models can answer many questions regarding protein conformational equilibrium and protein-ligand interactions, pH-sensitive phenomena such as acid-activated chaperones and amyloidogenic protein aggregation are inaccessible to such models. Constant pH molecular dynamics (CPHMD) coupled with the Generalized Born with a Simple sWitching function (GBSW) implicit solvent model provide an accurate framework for simulating pH sensitive processes in biological systems. Although this combination has demonstrated success in predicting pKa values of protein structures, and in exploring dynamics of ionizable side-chains, its speed has been an impediment to routine application. The recent availability of low-cost graphics processing unit (GPU) chipsets with thousands of processing cores, together with the implementation of the accurate GBSW implicit solvent model on those chipsets (Arthur and Brooks, J. Comput. Chem. 2016, 37, 927), provide an opportunity to improve the speed of CPHMD and ionization modeling greatly. Here, we present a first implementation of GPU-enabled CPHMD within the CHARMM-OpenMM simulation package interface. Depending on the system size and nonbonded force cutoff parameters, we find speed increases of between one and three orders of magnitude. Additionally, the algorithm scales better with system size than the CPU-based algorithm, thus allowing for larger systems to be modeled in a cost effective manner. We anticipate that the improved performance of this methodology will open the door for broad-spread application of CPHMD in its modeling pH-mediated biological processes. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Evan J Arthur
- Department of Chemistry, University of Michigan, 930 N. University Ave, Ann Arbor, Michigan, 48109
| | - Charles L Brooks
- Department of Chemistry and Biophysics Program, University of Michigan, 930 N. University Ave, Ann Arbor, Michigan, 48109
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28
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Wang B, Lou Z, Zhang H, Xu B. Effect of the electrostatic surface potential on the oligomerization of full-length human recombinant prion protein at single-molecule level. J Chem Phys 2016; 144:114701. [DOI: 10.1063/1.4943878] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Affiliation(s)
- Bin Wang
- Single Molecule Study Laboratory, College of Engineering and Nanoscale Science, and Engineering Center, University of Georgia, Athens, Georgia 30605, USA
| | - Zhichao Lou
- Single Molecule Study Laboratory, College of Engineering and Nanoscale Science, and Engineering Center, University of Georgia, Athens, Georgia 30605, USA
- College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, People’s Republic of China
| | - Haiqian Zhang
- College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, People’s Republic of China
| | - Bingqian Xu
- Single Molecule Study Laboratory, College of Engineering and Nanoscale Science, and Engineering Center, University of Georgia, Athens, Georgia 30605, USA
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29
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Abstract
Transition metal hydride complexes are usually amphoteric, not only acting as hydride donors, but also as Brønsted-Lowry acids. A simple additive ligand acidity constant equation (LAC for short) allows the estimation of the acid dissociation constant Ka(LAC) of diamagnetic transition metal hydride and dihydrogen complexes. It is remarkably successful in systematizing diverse reports of over 450 reactions of acids with metal complexes and bases with metal hydrides and dihydrogen complexes, including catalytic cycles where these reactions are proposed or observed. There are links between pKa(LAC) and pKa(THF), pKa(DCM), pKa(MeCN) for neutral and cationic acids. For the groups from chromium to nickel, tables are provided that order the acidity of metal hydride and dihydrogen complexes from most acidic (pKa(LAC) -18) to least acidic (pKa(LAC) 50). Figures are constructed showing metal acids above the solvent pKa scales and organic acids below to summarize a large amount of information. Acid-base features are analyzed for catalysts from chromium to gold for ionic hydrogenations, bifunctional catalysts for hydrogen oxidation and evolution electrocatalysis, H/D exchange, olefin hydrogenation and isomerization, hydrogenation of ketones, aldehydes, imines, and carbon dioxide, hydrogenases and their model complexes, and palladium catalysts with hydride intermediates.
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Affiliation(s)
- Robert H Morris
- Department of Chemistry, University of Toronto , 80 Saint George Street, Toronto, Ontario M5S 3H6, Canada
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30
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31
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Ramachandran P, Jagtap SS, Patel SKS, Li J, Chan Kang Y, Lee JK. Role of the non-conserved amino acid asparagine 285 in the glycone-binding pocket of Neosartorya fischeri β-glucosidase. RSC Adv 2016. [DOI: 10.1039/c5ra28017f] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neosartorya fischeriβ-glucosidase (NfBGL595) is distinguished from other BGLs by its high turnover forp-nitrophenyl β-d-glucopyranoside (pNPG) and flavones.
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Affiliation(s)
| | | | - Sanjay K. S. Patel
- Department of Chemical Engineering
- Konkuk University
- Gwangjin-Gu
- Republic of Korea
| | - Jinglin Li
- Department of Chemical Engineering
- Konkuk University
- Gwangjin-Gu
- Republic of Korea
| | - Yun Chan Kang
- Department of Material Science and Technology
- Korea University
- Republic of Korea
| | - Jung-Kul Lee
- Department of Chemical Engineering
- Konkuk University
- Gwangjin-Gu
- Republic of Korea
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32
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Bodnarchuk MS, Heyes DM, Dini D, Chahine S, Edwards S. Role of Deprotonation Free Energies in pKa Prediction and Molecule Ranking. J Chem Theory Comput 2015; 10:2537-45. [PMID: 26580774 DOI: 10.1021/ct400914w] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A computationally efficient classical molecular simulation technique is derived for ranking the pKa values of a set of chemically similar congeneric molecules in an implicit solvent model of water. This uses the deprotonation free energy of the titratable group in the gas and aqueous phases obtained by thermodynamic integration (TI). For a series of alcohols and acids a strong linear correlation is demonstrated between the experimental pKa and the deprotonation free energy difference in the gas and liquid phases. These calculations also show that classical TI is more efficient than slow-growth TI in calculating deprotonation free energies for the series of molecules considered herein.
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Affiliation(s)
- M S Bodnarchuk
- Department of Mechanical Engineering, Imperial College London , Exhibition Road, London, SW7 2AZ, U.K
| | - D M Heyes
- Department of Mechanical Engineering, Imperial College London , Exhibition Road, London, SW7 2AZ, U.K
| | - D Dini
- Department of Mechanical Engineering, Imperial College London , Exhibition Road, London, SW7 2AZ, U.K
| | - S Chahine
- BP Marine Limited, Marine Technology Centre , Whitchurch Hill, Pangbourne, RG8 7QR, U.K
| | - S Edwards
- BP Marine Limited, Marine Technology Centre , Whitchurch Hill, Pangbourne, RG8 7QR, U.K
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33
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Jain R, Kumar R, Kumar S, Chhabra R, Agarwal MC, Kumar R. Analysis of the pH-dependent stability and millisecond folding kinetics of horse cytochrome c. Arch Biochem Biophys 2015; 585:52-63. [DOI: 10.1016/j.abb.2015.09.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2015] [Revised: 09/10/2015] [Accepted: 09/14/2015] [Indexed: 11/26/2022]
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Conformational Dynamics and Binding Free Energies of Inhibitors of BACE-1: From the Perspective of Protonation Equilibria. PLoS Comput Biol 2015; 11:e1004341. [PMID: 26506513 PMCID: PMC4623973 DOI: 10.1371/journal.pcbi.1004341] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 05/17/2015] [Indexed: 11/19/2022] Open
Abstract
BACE-1 is the β-secretase responsible for the initial amyloidogenesis in Alzheimer’s disease, catalyzing hydrolytic cleavage of substrate in a pH-sensitive manner. The catalytic mechanism of BACE-1 requires water-mediated proton transfer from aspartyl dyad to the substrate, as well as structural flexibility in the flap region. Thus, the coupling of protonation and conformational equilibria is essential to a full in silico characterization of BACE-1. In this work, we perform constant pH replica exchange molecular dynamics simulations on both apo BACE-1 and five BACE-1-inhibitor complexes to examine the effect of pH on dynamics and inhibitor binding properties of BACE-1. In our simulations, we find that solution pH controls the conformational flexibility of apo BACE-1, whereas bound inhibitors largely limit the motions of the holo enzyme at all levels of pH. The microscopic pKa values of titratable residues in BACE-1 including its aspartyl dyad are computed and compared between apo and inhibitor-bound states. Changes in protonation between the apo and holo forms suggest a thermodynamic linkage between binding of inhibitors and protons localized at the dyad. Utilizing our recently developed computational protocol applying the binding polynomial formalism to the constant pH molecular dynamics (CpHMD) framework, we are able to obtain the pH-dependent binding free energy profiles for various BACE-1-inhibitor complexes. Our results highlight the importance of correctly addressing the binding-induced protonation changes in protein-ligand systems where binding accompanies a net proton transfer. This work comprises the first application of our CpHMD-based free energy computational method to protein-ligand complexes and illustrates the value of CpHMD as an all-purpose tool for obtaining pH-dependent dynamics and binding free energies of biological systems. Formation of insoluble amyloid plaques in the vascular and hippocampal areas of the brain characterizes Alzheimer’s disease, a devastating neurodegenerative disorder causing dementia. Site-specific hydrolytic catalysis of β-secretase, or BACE-1, is responsible for production of oligomerative amyloid β-peptide. As the catalytic activity of BACE-1 is pH-dependent and its structural dynamics are intrinsic to the catalysis, we examine the dependence of dynamics of BACE-1 on solution pH and its implications on the catalytic mechanism of BACE-1. Also, we highlight the importance of accurate description of protonation states of the titratable groups in computer-aided drug discovery targeting BACE-1. We hope the understanding of pH dependence of the dynamics and inhibitor binding properties of BACE-1 will aid the structure-based inhibitor design efforts against Alzheimer’s disease.
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35
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Feliks M, Field MJ. Pcetk: A pDynamo-based Toolkit for Protonation State Calculations in Proteins. J Chem Inf Model 2015; 55:2288-96. [DOI: 10.1021/acs.jcim.5b00262] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mikolaj Feliks
- Université Grenoble Alpes, IBS, F-38044 Grenoble, France
- CNRS, IBS, F-38044 Grenoble, France
- CEA, IBS, F-38044 Grenoble, France
| | - Martin J. Field
- Université Grenoble Alpes, IBS, F-38044 Grenoble, France
- CNRS, IBS, F-38044 Grenoble, France
- CEA, IBS, F-38044 Grenoble, France
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Bai W, Zhou C, Zhao Y, Wang Q, Ma Y. Structural Insight into and Mutational Analysis of Family 11 Xylanases: Implications for Mechanisms of Higher pH Catalytic Adaptation. PLoS One 2015; 10:e0132834. [PMID: 26161643 PMCID: PMC4498622 DOI: 10.1371/journal.pone.0132834] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 06/18/2015] [Indexed: 11/25/2022] Open
Abstract
To understand the molecular basis of higher pH catalytic adaptation of family 11 xylanases, we compared the structures of alkaline, neutral, and acidic active xylanases and analyzed mutants of xylanase Xyn11A-LC from alkalophilic Bacillus sp. SN5. It was revealed that alkaline active xylanases have increased charged residue content, an increased ratio of negatively to positively charged residues, and decreased Ser, Thr, and Tyr residue content relative to non-alkaline active counterparts. Between strands β6 and β7, alkaline xylanases substitute an α-helix for a coil or turn found in their non-alkaline counterparts. Compared with non-alkaline xylanases, alkaline active enzymes have an inserted stretch of seven amino acids rich in charged residues, which may be beneficial for xylanase function in alkaline conditions. Positively charged residues on the molecular surface and ionic bonds may play important roles in higher pH catalytic adaptation of family 11 xylanases. By structure comparison, sequence alignment and mutational analysis, six amino acids (Glu16, Trp18, Asn44, Leu46, Arg48, and Ser187, numbering based on Xyn11A-LC) adjacent to the acid/base catalyst were found to be responsible for xylanase function in higher pH conditions. Our results will contribute to understanding the molecular mechanisms of higher pH catalytic adaptation in family 11 xylanases and engineering xylanases to suit industrial applications.
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Affiliation(s)
- Wenqin Bai
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, China
- National Engineering Laboratory for Industrial Enzymes, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
- School of Life Science, Shanxi Normal University, Linfen, 041004, China
- * E-mail: (YHM); (WQB)
| | - Cheng Zhou
- National Engineering Laboratory for Industrial Enzymes, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Yueju Zhao
- Institute of Agro-Products Processing Science and Technology, Chinese Academy of Agriculture Sciences, Beijing, 100193, China
| | - Qinhong Wang
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, China
| | - Yanhe Ma
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, China
- National Engineering Laboratory for Industrial Enzymes, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
- * E-mail: (YHM); (WQB)
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Dabirmanesh B, Khajeh K, Ghazi F, Ranjbar B, Etezad SM. A semi-rational approach to obtain an ionic liquid tolerant bacterial laccase through π-type interactions. Int J Biol Macromol 2015; 79:822-9. [PMID: 26054663 DOI: 10.1016/j.ijbiomac.2015.06.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Revised: 05/30/2015] [Accepted: 06/02/2015] [Indexed: 11/25/2022]
Abstract
Laccases are particularly promising enzymes for biotechnology and bioremediation purposes. They are among the most effective enzymes capable of catalyzing the degradation of phenolic compounds with poor water solubility. The technological utility of lacasses can be enhanced greatly by their use in ionic liquids rather than in conventional organic solvents or in their natural aqueous reaction media. In the current study, a laccase from Bacillus HR03 has been engineered through a semi rational method. By screening a library of 450 clones, Glu188Tyr and Glu188Phe showed a distinct improvement in thermal stability and ionic liquid tolerance. In comparison with the wild type, selected mutants exhibited higher kcat/Km against ABTS in the imidazolium based ionic liquids, (1-ethyl-3-methyl imidazolium chloride [EMIm][Cl], butyl-3-methyl imidazolium chloride [BMIm][Cl] and hexyl-3-methyl imidazolium chloride [HMIm][Cl]). Glu188Tyr had a catalytic efficiency, two times greater when compared to the wild type in [HMIm][Cl]. Far-UV circular dichroism (CD) exhibited no significant changes in the secondary structure of the mutants and wild type. Glu188Tyr revealed a more compact structure using Near-UV CD and fluorescence spectroscopy that could account for its high thermal stability. According to bioinformatic analysis, π-π and anion-π interactions played the dominant role in stabilizing both variants.
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Affiliation(s)
- Bahareh Dabirmanesh
- Department of Biochemistry, Faculty of Biological Science, Tarbiat Modares University, Tehran, Iran
| | - Khosro Khajeh
- Department of Biochemistry, Faculty of Biological Science, Tarbiat Modares University, Tehran, Iran.
| | - Farideh Ghazi
- Department of Genetics and Molecular Biology, Medical School, Iran University of Medical Sciences, Tehran, Iran
| | - Bijan Ranjbar
- Department of Biophysics, Faculty of Biological Science, Tarbiat Modares University, Tehran, Iran
| | - Seyed-Masoud Etezad
- Department of Organic Colorants, Institute for Color Science and Technology, Tehran, Iran
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38
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Wallerstein J, Weininger U, Khan MAI, Linse S, Akke M. Site-specific protonation kinetics of acidic side chains in proteins determined by pH-dependent carboxyl (13)C NMR relaxation. J Am Chem Soc 2015; 137:3093-101. [PMID: 25665463 DOI: 10.1021/ja513205s] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Proton-transfer dynamics plays a critical role in many biochemical processes, such as proton pumping across membranes and enzyme catalysis. The large majority of enzymes utilize acid-base catalysis and proton-transfer mechanisms, where the rates of proton transfer can be rate limiting for the overall reaction. However, measurement of proton-exchange kinetics for individual side-chain carboxyl groups in proteins has been achieved in only a handful of cases, which typically have involved comparative analysis of mutant proteins in the context of reaction network modeling. Here we describe an approach to determine site-specific protonation and deprotonation rate constants (kon and koff, respectively) of carboxyl side chains, based on (13)C NMR relaxation measurements as a function of pH. We validated the method using an extensively studied model system, the B1 domain of protein G, for which we measured rate constants koff in the range (0.1-3) × 10(6) s(-1) and kon in the range (0.6-300) × 10(9) M(-1) s(-1), which correspond to acid-base equilibrium dissociation constants (Ka) in excellent agreement with previous results determined by chemical shift titrations. Our results further reveal a linear free-energy relationship between log kon and pKa, which provides information on the free-energy landscape of the protonation reaction, showing that the variability among residues in these parameters arises primarily from the extent of charge stabilization of the deprotonated state by the protein environment. We find that side-chain carboxyls with extreme values of koff or kon are involved in hydrogen bonding, thus providing a mechanistic explanation for the observed stabilization of the protonated or deprotonated state.
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Affiliation(s)
- Johan Wallerstein
- Department of Biophysical Chemistry and ‡Department of Biochemistry and Structural Biology, Center for Molecular Protein Science, Lund University , P.O. Box 124, SE-221 00 Lund, Sweden
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39
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Kantardjiev AA. irGPU.proton.Net: Irregular strong charge interaction networks of protonatable groups in protein molecules--a GPU solver using the fast multipole method and statistical thermodynamics. J Comput Chem 2015; 36:689-93. [PMID: 25650055 DOI: 10.1002/jcc.23842] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 12/04/2014] [Accepted: 12/24/2014] [Indexed: 11/08/2022]
Abstract
MOTIVATION A cluster of strongly interacting ionization groups in protein molecules with irregular ionization behavior is suggestive for specific structure-function relationship. However, their computational treatment is unconventional (e.g., lack of convergence in naive self-consistent iterative algorithm). The stringent evaluation requires evaluation of Boltzmann averaged statistical mechanics sums and electrostatic energy estimation for each microstate. SUMMARY irGPU: Irregular strong interactions in proteins--a GPU solver is novel solution to a versatile problem in protein biophysics--atypical protonation behavior of coupled groups. The computational severity of the problem is alleviated by parallelization (via GPU kernels) which is applied for the electrostatic interaction evaluation (including explicit electrostatics via the fast multipole method) as well as statistical mechanics sums (partition function) estimation. Special attention is given to the ease of the service and encapsulation of theoretical details without sacrificing rigor of computational procedures. irGPU is not just a solution-in-principle but a promising practical application with potential to entice community into deeper understanding of principles governing biomolecule mechanisms.
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Affiliation(s)
- Alexander A Kantardjiev
- Institute of Organic Chemistry, Nuclear Magnetic Resonance Lab, Bulgarian Academy of Sciences, Reduta, ul. Acad Bontchev Street, Sofia, 1000, Bulgaria
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40
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Jungles JM, Dukes MP, Vunnam N, Pedigo S. Impact of pH on the structure and function of neural cadherin. Biochemistry 2014; 53:7436-44. [PMID: 25365402 DOI: 10.1021/bi5010798] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Neural (N-) cadherin is a transmembrane protein within adherens junctions that mediates cell-cell adhesion. It has 5 modular extracellular domains (EC1-EC5) that bind 3 calcium ions between each of the modules. Calcium binding is required for dimerization. N-Cadherin is involved in diverse processes including tissue morphogenesis, excitatory synapse formation and dynamics, and metastasis of cancer. During neurotransmission and tumorigenesis, fluctuations in extracellular pH occur, causing tissue acidosis with associated physiological consequences. Studies reported here aim to determine the effect of pH on the dimerization properties of a truncated construct of N-cadherin containing EC1-EC2. Since N-cadherin is an anionic protein, we hypothesized that acidification of solution would cause an increase in stability of the apo protein, a decrease in the calcium-binding affinity, and a concomitant decrease in the formation of adhesive dimer. The stability of the apo monomer was increased and the calcium-binding affinity was decreased at reduced pH, consistent with our hypothesis. Surprisingly, analytical SEC studies showed an increase in calcium-induced dimerization as solution pH decreased from 7.4 to 5.0. Salt-dependent dimerization studies indicated that electrostatic repulsion attenuates dimerization affinity. These results point to a possible electrostatic mechanism for moderating dimerization affinity of the Type I cadherin family. Extrapolating these results to cell adhesion in vivo leads to the assertion that decreased pH promotes adhesion by N-cadherin, thereby stabilizing synaptic junctions.
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Affiliation(s)
- Jared M Jungles
- Department of Chemistry and Biochemistry, University of Mississippi , University, Mississippi 38677, United States
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41
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Goh GB, Hulbert BS, Zhou H, Brooks CL. Constant pH molecular dynamics of proteins in explicit solvent with proton tautomerism. Proteins 2014; 82:1319-31. [PMID: 24375620 DOI: 10.1002/prot.24499] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 11/13/2013] [Accepted: 12/12/2013] [Indexed: 12/14/2022]
Abstract
pH is a ubiquitous regulator of biological activity, including protein-folding, protein-protein interactions, and enzymatic activity. Existing constant pH molecular dynamics (CPHMD) models that were developed to address questions related to the pH-dependent properties of proteins are largely based on implicit solvent models. However, implicit solvent models are known to underestimate the desolvation energy of buried charged residues, increasing the error associated with predictions that involve internal ionizable residue that are important in processes like hydrogen transport and electron transfer. Furthermore, discrete water and ions cannot be modeled in implicit solvent, which are important in systems like membrane proteins and ion channels. We report on an explicit solvent constant pH molecular dynamics framework based on multi-site λ-dynamics (CPHMD(MSλD)). In the CPHMD(MSλD) framework, we performed seamless alchemical transitions between protonation and tautomeric states using multi-site λ-dynamics, and designed novel biasing potentials to ensure that the physical end-states are predominantly sampled. We show that explicit solvent CPHMD(MSλD) simulations model realistic pH-dependent properties of proteins such as the Hen-Egg White Lysozyme (HEWL), binding domain of 2-oxoglutarate dehydrogenase (BBL) and N-terminal domain of ribosomal protein L9 (NTL9), and the pKa predictions are in excellent agreement with experimental values, with a RMSE ranging from 0.72 to 0.84 pKa units. With the recent development of the explicit solvent CPHMD(MSλD) framework for nucleic acids, accurate modeling of pH-dependent properties of both major class of biomolecules-proteins and nucleic acids is now possible.
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Affiliation(s)
- Garrett B Goh
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, 48109
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42
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Schwans JP, Sunden F, Gonzalez A, Tsai Y, Herschlag D. Uncovering the determinants of a highly perturbed tyrosine pKa in the active site of ketosteroid isomerase. Biochemistry 2013; 52:7840-55. [PMID: 24151972 PMCID: PMC3890242 DOI: 10.1021/bi401083b] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Within the idiosyncratic enzyme active-site environment, side chain and ligand pKa values can be profoundly perturbed relative to their values in aqueous solution. Whereas structural inspection of systems has often attributed perturbed pKa values to dominant contributions from placement near charged groups or within hydrophobic pockets, Tyr57 of a Pseudomonas putida ketosteroid isomerase (KSI) mutant, suggested to have a pKa perturbed by nearly 4 units to 6.3, is situated within a solvent-exposed active site devoid of cationic side chains, metal ions, or cofactors. Extensive comparisons among 45 variants with mutations in and around the KSI active site, along with protein semisynthesis, (13)C NMR spectroscopy, absorbance spectroscopy, and X-ray crystallography, was used to unravel the basis for this perturbed Tyr pKa. The results suggest that the origin of large energetic perturbations are more complex than suggested by visual inspection. For example, the introduction of positively charged residues near Tyr57 raises its pKa rather than lowers it; this effect, and part of the increase in the Tyr pKa from the introduction of nearby anionic groups, arises from accompanying active-site structural rearrangements. Other mutations with large effects also cause structural perturbations or appear to displace a structured water molecule that is part of a stabilizing hydrogen-bond network. Our results lead to a model in which three hydrogen bonds are donated to the stabilized ionized Tyr, with these hydrogen-bond donors, two Tyr side chains, and a water molecule positioned by other side chains and by a water-mediated hydrogen-bond network. These results support the notion that large energetic effects are often the consequence of multiple stabilizing interactions rather than a single dominant interaction. Most generally, this work provides a case study for how extensive and comprehensive comparisons via site-directed mutagenesis in a tight feedback loop with structural analysis can greatly facilitate our understanding of enzyme active-site energetics. The extensive data set provided may also be a valuable resource for those wishing to extensively test computational approaches for determining enzymatic pKa values and energetic effects.
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Affiliation(s)
- Jason P. Schwans
- Department of Biochemistry, Stanford University, Stanford, California 94305
| | - Fanny Sunden
- Department of Biochemistry, Stanford University, Stanford, California 94305
| | - Ana Gonzalez
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025
| | - Yingssu Tsai
- Department of Chemistry, Stanford University, Stanford, California 94305
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025
| | - Daniel Herschlag
- Department of Biochemistry, Stanford University, Stanford, California 94305
- Department of Chemistry, Stanford University, Stanford, California 94305
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43
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Mironov VA, Khrenova MG, Grigorenko BL, Savitsky AP, Nemukhin AV. Thermal isomerization of the chromoprotein asFP595 and its kindling mutant A143G: QM/MM molecular dynamics simulations. J Phys Chem B 2013; 117:13507-14. [PMID: 24079704 DOI: 10.1021/jp407406k] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Chromoprotein asFP595 and its A143G variant called kindling fluorescent protein (KFP) are among the chronologically first species for which trans-cis chromophore isomerization has been proposed as a driving force of photoswitching. In spite of long-lasting efforts to characterize the route between protein conformations referring to the trans and cis forms of the chromophore, the molecular mechanism of this transformation is still under debate. We report the results of computational studies of the trans-cis isomerization of the anionic and neutral chromophore inside the protein matrices in the ground electronic state for both variants, asFP595 and KFP. Corresponding free energy profiles (potentials of mean force) were evaluated by using molecular dynamics simulations with the quantum mechanical-molecular mechanical (QM/MM) forces. The computed free energy barrier for the cis-trans ground state (thermal) isomerization reaction is about 2 kcal/mol higher in KFP than that in asFP595. These results provide interpretation of experimental studies on thermal relaxation from the light-induced activation of fluorescence of these proteins and correctly show that the A143G mutation in asFP595 noticeably increases the lifetime of the fluorescence species.
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Affiliation(s)
- Vladimir A Mironov
- Department of Chemistry, M.V. Lomonosov Moscow State University , Leninskie Gory, 1/3, Moscow, 119991, Russian Federation
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44
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Naseem S, Laurent AD, Carroll EC, Vengris M, Kumauchi M, Hoff WD, Krylov AI, Larsen DS. Photo-isomerization upshifts the pKa of the Photoactive Yellow Protein chromophore to contribute to photocycle propagation. J Photochem Photobiol A Chem 2013. [DOI: 10.1016/j.jphotochem.2013.06.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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45
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Karshikoff A, Nilsson L, Foloppe N. Understanding the −C–X1–X2–C– Motif in the Active Site of the Thioredoxin Superfamily: E. coli DsbA and Its Mutants as a Model System. Biochemistry 2013; 52:5730-45. [DOI: 10.1021/bi400500e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Andrey Karshikoff
- Institute of Molecular Biology, Bulgarian Academy of Sciences, Acad. G. Bonchev Str.,
bl. 21, Sofia 1113, Bulgaria
| | - Lennart Nilsson
- Department of Biosciences and
Nutrition, Center for Biosciences, Karolinska Institutet, S-141 83 Huddinge, Sweden
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46
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Tripathy DR, Dinda AK, Dasgupta S. A simple assay for the ribonuclease activity of ribonucleases in the presence of ethidium bromide. Anal Biochem 2013; 437:126-9. [PMID: 23499964 DOI: 10.1016/j.ab.2013.03.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 02/28/2013] [Accepted: 03/01/2013] [Indexed: 11/30/2022]
Abstract
The ribonuclease (RNase) activity of ribonucleases has been assayed by observing the change in fluorescence intensity of ethidium bromide on binding with yeast RNA. The binding of EtBr with RNA was monitored via UV-vis and fluorimetric methods. The degradation of RNA by RNase A was monitored by the change in fluorescence emission intensity of ethidium bromide at 600nm on excitation at 510nm. The ribonucleolytic activity of RNase A and angiogenin at various pH values was determined by this method. From this technique we have also determined the macroscopic pKa values of active site residues of these enzymes. This assay permits the evaluation of the catalytic efficiency of enzymatic proteins ranging from high ribonucleolytic activity to low ribonucleolytic activity toward the natural substrate RNA.
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Affiliation(s)
- Debi Ranjan Tripathy
- Department of Chemistry, Indian Institute of Technology, Kharagpur, Kharagpur 721302, India
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47
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Ozcan A, Olmez EO, Alakent B. Effects of protonation state of Asp181 and position of active site water molecules on the conformation of PTP1B. Proteins 2013; 81:788-804. [PMID: 23239271 DOI: 10.1002/prot.24234] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 10/19/2012] [Accepted: 12/05/2012] [Indexed: 12/11/2022]
Abstract
In protein tyrosine phosphatase 1B (PTP1B), the flexible WPD loop adopts a closed conformation (WPDclosed ) in the active state of PTP1B, bringing the catalytic Asp181 close to the active site pocket, while WPD loop is in an open conformation (WPDopen ) in the inactive state. Previous studies showed that Asp181 may be protonated at physiological pH, and ordered water molecules exist in the active site. In the current study, molecular dynamics simulations are employed at different Asp181 protonation states and initial positions of active site water molecules, and compared with the existing crystallographic data of PTP1B. In WPDclosed conformation, the active site is found to maintain its conformation only in the protonated state of Asp181 in both free and liganded states, while Asp181 is likely to be deprotonated in WPDopen conformation. When the active site water molecule network that is a part of the free WPDclosed crystal structure is disrupted, intermediate WPD loop conformations, similar to that in the PTPRR crystal structure, are sampled in the MD simulations. In liganded PTP1B, one active site water molecule is found to be important for facilitating the orientation of Cys215 and the phosphate ion, thus may play a role in the reaction. In conclusion, conformational stability of WPD loop, and possibly catalytic activity of PTP1B, is significantly affected by the protonation state of Asp181 and position of active site water molecules, showing that these aspects should be taken into consideration both in MD simulations and inhibitor design.
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Affiliation(s)
- Ahmet Ozcan
- Graduate Program in Computational Science and Engineering, Bogazici University, Bebek, Istanbul 34342, Turkey
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48
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Roos G, Foloppe N, Messens J. Understanding the pK(a) of redox cysteines: the key role of hydrogen bonding. Antioxid Redox Signal 2013; 18:94-127. [PMID: 22746677 DOI: 10.1089/ars.2012.4521] [Citation(s) in RCA: 168] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Many cellular functions involve cysteine chemistry via thiol-disulfide exchange pathways. The nucleophilic cysteines of the enzymes involved are activated as thiolate. A thiolate is much more reactive than a neutral thiol. Therefore, determining and understanding the pK(a)s of functional cysteines are important aspects of biochemistry and molecular biology with direct implications for redox signaling. Here, we describe the experimental and theoretical methods to determine cysteine pK(a) values, and we examine the factors that control these pK(a)s. Drawing largely on experience gained with the thioredoxin superfamily, we examine the roles of solvation, charge-charge, helix macrodipole, and hydrogen bonding interactions as pK(a)-modulating factors. The contributions of these factors in influencing cysteine pK(a)s and the associated chemistry, including the relevance for the reaction kinetics and thermodynamics, are discussed. This analysis highlights the critical role of direct hydrogen bonding to the cysteine sulfur as a key factor modulating the equilibrium between thiol S-H and thiolate S(-). This role is easily understood intuitively and provides a framework for biochemical functional insights.
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Affiliation(s)
- Goedele Roos
- General Chemistry, Vrije University Brussel, Brussels, Belgium
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49
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Liu Y, Hu B, Xu Y, Bo J, Fan S, Wang J, Lu F. Improvement of the acid stability of Bacillus licheniformis alpha amylase by error-prone PCR. J Appl Microbiol 2012; 113:541-9. [DOI: 10.1111/j.1365-2672.2012.05359.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2012] [Revised: 05/25/2012] [Accepted: 05/28/2012] [Indexed: 11/27/2022]
Affiliation(s)
| | | | | | | | | | - J.L. Wang
- College of Biotechnology; Tianjin University of Science & Technology; Tianjin; China
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50
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Gene cloning, expression, and biochemical characterization of an alkali-tolerant β-mannanase from Humicola insolens Y1. ACTA ACUST UNITED AC 2012; 39:547-55. [DOI: 10.1007/s10295-011-1067-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Accepted: 11/21/2011] [Indexed: 10/14/2022]
Abstract
Abstract
In this article, we firstly report a highly alkali-tolerant fungal β-mannanase from Humicola insolens Y1. The full-length cDNA of the β-mannanase, designated as man5A, has an open reading frame of 1,233 bp that encodes a 411-amino acid polypeptide (Man5A) with a calculated molecular mass of 42.3 kDa. The deduced sequence of Man5A comprises a putative 20-residue signal peptide and a catalytic domain belonging to glycoside hydrolase family 5, and displays 61–85% identities with hypothetical proteins and 32–39% with experimentally verified fungal β-mannanases. Purified recombinant Man5A produced by Pichia pastoris has a specific activity of 1,122 U mg−1 and exhibits optimal activity at pH 5.5 and 70°C. Distinct from other reported fungal β-mannanases, Man5A is highly alkali tolerant, exhibiting 45 and 36% of the maximal activity at pH 8.0 and 9.0, respectively, and more than 10% activity even at pH 10.0. Moreover, Man5A has excellent pH stability at pH 5.0–12.0 and is highly thermostable at 50°C. The higher frequency of alkaline amino acids (Arg and Lys), greater pKa values of the catalytic residues, and more positively charged residues on the surface of Man5A might be the causes. Man5A has strong resistance to various neutral and alkaline proteases, retaining more than 97% of the activity after proteolytic treatment for 1 h. The superior characteristics of Man5A make it more advantageous for the application in the kraft pulp industry.
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