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Gao M, Huang Y. Molecular dynamics simulations revealed topological frustration in the binding-wrapping process of eIF4G with eIF4E. Phys Chem Chem Phys 2024; 26:2073-2081. [PMID: 38131207 DOI: 10.1039/d3cp04899c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
Interaction between the cap-binding protein eIF4E and the scaffolding protein eIF4G is essential for the cap-dependent translation initiation in eukaryotes. In the Saccharomyces cerevisiae eIF4G/eIF4E complex, the intrinsically disordered eIF4E-binding domain of eIF4G folds into a bracelet-like structure upon binding to eIF4E. Aiming to unveil the molecular mechanism underlying the binding-wrapping process of eIF4G with eIF4E, we performed extensive coarse-grained molecular dynamics simulations and transition path analysis in this work. The major transition pathway revealed from our simulations showed that docking of the eIF4E-binding motif of eIF4G to the folded core of eIF4E initiates the binding process and then the disordered eIF4G wraps around the N-terminal tail of eIF4E. Additionally, we identified a minor transition pathway which indicates the involvement of topological frustration in the binding process. By manipulating the interaction strength of the wrapping contacts and the latching contacts, we further dissected factors affecting the formation of topological frustration and the binding transition kinetics. Our findings provide new clues for experimental studies on the binding mechanism of eIF4G to eIF4E in the future and exemplify the involvement of topological frustration in the binding process of intrinsically disordered proteins.
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Affiliation(s)
- Meng Gao
- Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan 430068, China.
- Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Hubei University of Technology, Wuhan 430068, China
- Key Laboratory of Industrial Fermentation (Ministry of Education), Hubei University of Technology, Wuhan 430068, China
| | - Yongqi Huang
- Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan 430068, China.
- Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Hubei University of Technology, Wuhan 430068, China
- Key Laboratory of Industrial Fermentation (Ministry of Education), Hubei University of Technology, Wuhan 430068, China
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2
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Agarwala P, Ghosh A, Hazarika P, Acharjee D, Ghosh S, Rout D, Sasmal DK. Unraveling the Interaction of Diflunisal with Cyclodextrin and Lysozyme by Fluorescence Spectroscopy. J Phys Chem B 2023; 127:9710-9723. [PMID: 37917720 DOI: 10.1021/acs.jpcb.3c04295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2023]
Abstract
Understanding the interaction between the drug:carrier complex and protein is essential for the development of a new drug-delivery system. However, the majority of reports are based on an understanding of interactions between the drug and protein. Here, we present our findings on the interaction of the anti-inflammatory drug diflunisal with the drug carrier cyclodextrin (CD) and the protein lysozyme, utilizing steady-state and time-resolved fluorescence spectroscopy. Our findings reveal a different pattern of molecular interaction between the inclusion complex of β-CD (β-CD) or hydroxypropyl-β-CD (HP-β-CD) (as the host) and diflunisal (as the guest) in the presence of protein lysozyme. The quantum yield for the 1:2 guest:host complex is twice that of the 1:1 guest:host complex, indicating a more stable hydrophobic microenvironment created in the 1:2 complex. Consequently, the nonradiative decay pathway is significantly reduced. The interaction is characterized by ultrafast solvation dynamics and time-resolved fluorescence resonance energy transfer. The solvation dynamics of the lysozyme becomes 10% faster under the condition of binding with the drug, indicating a negligible change in the polar environment after binding. In addition, the fluorescence lifetime of diflunisal (acceptor) is increased by 50% in the presence of the lysozyme (donor), which indicates that the drug molecule is bound to the binding pocket on the surface of the protein, and the average distance between active tryptophan in the hydrophobic region and diflunisal is calculated to be approximately 50 Å. Excitation and emission matrix spectroscopy reveals that the tryptophan emission increases 3-5 times in the presence of both diflunisal and CD. This indicates that the tryptophan of lysozyme may be present in a more hydrophobic environment in the presence of both diflunisal and CD. Our observations on the interaction of diflunisal with β-CD and lysozyme are well supported by molecular dynamics simulation. Results from this study may have an impact on the development of a better drug-delivery system in the future. It also reveals a fundamental molecular mechanism of interaction of the drug-carrier complex with the protein.
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Affiliation(s)
- Pratibha Agarwala
- Department of Chemistry, Indian Institute of Technology Jodhpur, Jodhpur, Rajasthan 342037, India
| | - Arabinda Ghosh
- Department of Computational Biology and Biotechnology, Mahapurusha Srimanta Sankaradeva Viswavidyalaya, Guwahati Unit, Guwahati, Assam 781032, India
| | - Priyanka Hazarika
- Department of Chemistry, Indian Institute of Technology Jodhpur, Jodhpur, Rajasthan 342037, India
| | - Debopam Acharjee
- School of Chemical Sciences, National Institute of Science Education and Research, An OCC of Homi Bhabha National Institute (HBNI), Khurda, Odisha 752050, India
| | - Shirsendu Ghosh
- Department of Chemistry, Gandhi Institute of Technology and Management (GITAM), Hyderabad Campus, Hyderabad 502329, India
| | - Debasish Rout
- Department of Chemistry, Indian Institute of Technology Jodhpur, Jodhpur, Rajasthan 342037, India
| | - Dibyendu K Sasmal
- Department of Chemistry, Indian Institute of Technology Jodhpur, Jodhpur, Rajasthan 342037, India
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3
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Ermakova E, Makshakova O, Zuev Y, Sedov I. Beta-rich intermediates in denaturation of lysozyme: accelerated molecular dynamics simulations. J Biomol Struct Dyn 2022; 40:13953-13964. [PMID: 34751100 DOI: 10.1080/07391102.2021.1997823] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Amyloid fibrillar aggregates play a critical role in many neurodegenerative disorders. Conversion of globular proteins into fibrils is associated with global conformational rearrangement and involves the transformation of α-helices to β-sheets. In the present work, the accelerated molecular dynamics technique was applied to study the unfolding of hen egg-white lysozyme at elevated temperatures, and the transformation of the native structure to a disordered one was analyzed. The influence of the disulfide bonds on the conformational dynamics and the energy landscape of denaturation process was considered. Our results show that formation of the metastable β-enriched conformers of individual protein molecules may precede the aggregation process. These β-rich intermediates can play a role of bricks making up fibrils.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Elena Ermakova
- FRC Kazan Scientific Center of RAS, Kazan Institute of Biochemistry and Biophysics, Kazan, Russia.,Sirius University of Science and Technology, Sochi, Russia
| | - Olga Makshakova
- FRC Kazan Scientific Center of RAS, Kazan Institute of Biochemistry and Biophysics, Kazan, Russia.,Sirius University of Science and Technology, Sochi, Russia
| | - Yuriy Zuev
- FRC Kazan Scientific Center of RAS, Kazan Institute of Biochemistry and Biophysics, Kazan, Russia
| | - Igor Sedov
- Sirius University of Science and Technology, Sochi, Russia.,Kazan Federal University, Kazan, Russia
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4
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Hendrix E, Motta S, Gahl RF, He Y. Insight into the Initial Stages of the Folding Process in Onconase Revealed by UNRES. J Phys Chem B 2022; 126:7934-7942. [PMID: 36179061 DOI: 10.1021/acs.jpcb.2c04770] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The unfolded state of proteins presents many challenges to elucidate the structural basis for biological function. This state is characterized by a large degree of structural heterogeneity which makes it difficult to generate structural models. However, recent experiments into the initial folding events of the 104-residue ribonuclease homologue onconase (ONC) were able to identify the regions in the protein that participate in the initial folding of this protein. Therefore, to gain additional structural insight into the unfolded state of proteins, this study utilized molecular dynamics simulations using the UNited-RESidue (UNRES) force field to evaluate whether there is a good agreement between the experimentally determined initial structures and the structures identified by computer simulations along a folding pathway. Indeed, these UNRES simulations accurately identified the two regions experimentally observed to form the initial native structure along the folding pathway of ONC. In addition, these regions are determined to be chain folding initiation sites (CFIS) according to methods developed previously. Subsequent self-organization maps (SOM) analysis has revealed key structural states involved in these early folding events.
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Affiliation(s)
- Emily Hendrix
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico87131, United States
| | - Stefano Motta
- Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milan20126, Italy
| | - Robert F Gahl
- Division of Extramural Activities, National Cancer Institute, National Institutes of Health, Bethesda, Maryland20850, United States
| | - Yi He
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico87131, United States.,Translational Informatics Division, Department of Internal Medicine, University of New Mexico, Albuquerque, New Mexico87131, United States
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5
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Bartoccini F, Retini M, Crinelli R, Menotta M, Fraternale A, Piersanti G. Dithiol Based on l-Cysteine and Cysteamine as a Disulfide-Reducing Agent. J Org Chem 2022; 87:10073-10079. [PMID: 35862282 PMCID: PMC9361291 DOI: 10.1021/acs.joc.2c01050] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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We report the synthesis, chemical properties, and disulfide
bond-reducing
performance of a dithiol called NACMEAA, conceived as a hybrid of
two biologically relevant thiols: cysteine and cysteamine. NACMEAA
is conveniently prepared from inexpensive l-cystine in an
efficient manner. As a nonvolatile, highly soluble, and neutral compound
at physiological pH with the first thiol pKa value of 8.0, NACMEAA is reactive and user-friendly. We also demonstrate
that NACMEAA reduces disulfide bonds in GSSG and lysozyme.
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Affiliation(s)
- Francesca Bartoccini
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, Piazza Rinascimento 6, 61029 Urbino, PU, Italy
| | - Michele Retini
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, Piazza Rinascimento 6, 61029 Urbino, PU, Italy
| | - Rita Crinelli
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, Piazza Rinascimento 6, 61029 Urbino, PU, Italy
| | - Michele Menotta
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, Piazza Rinascimento 6, 61029 Urbino, PU, Italy
| | - Alessandra Fraternale
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, Piazza Rinascimento 6, 61029 Urbino, PU, Italy
| | - Giovanni Piersanti
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, Piazza Rinascimento 6, 61029 Urbino, PU, Italy
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6
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Refolding of Lysozyme in Glycerol as Studied by Fast Scanning Calorimetry. Int J Mol Sci 2022; 23:ijms23052773. [PMID: 35269914 PMCID: PMC8911483 DOI: 10.3390/ijms23052773] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Revised: 02/22/2022] [Accepted: 02/26/2022] [Indexed: 02/01/2023] Open
Abstract
The folding of lysozyme in glycerol was monitored by the fast scanning calorimetry technique. Application of a temperature–time profile with an isothermal segment for refolding allowed assessment of the state of the non-equilibrium protein ensemble and gave information on the kinetics of folding. We found that the non-equilibrium protein ensemble mainly contains a mixture of unfolded and folded protein forms and partially folded intermediates, and enthalpic barriers control the kinetics of the process. Lysozyme folding in glycerol follows the same or similar triangular mechanism described in the literature for folding in water. The unfolding enthalpy of the intermediate must be no lower than 70% of the folded form, while the activation barrier for the unfolding of the intermediate (ca. 140 kJ/mol) is about 100 kJ/mol lower than that of the folded form (ca. 240–260 kJ/mol).
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7
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Silva-Costa LC, Smith BJ. Post-translational Modifications in Brain Diseases: A Future for Biomarkers. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1382:129-141. [DOI: 10.1007/978-3-031-05460-0_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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8
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Islam S, Mukhopadhyay C. Aggregation of Lysozyme in the Presence of a Mixed Bilayer of POPC and POPG. ACS OMEGA 2021; 6:17861-17869. [PMID: 34308021 PMCID: PMC8295997 DOI: 10.1021/acsomega.1c01145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 06/30/2021] [Indexed: 05/04/2023]
Abstract
Understanding the molecular mechanisms by which amyloidogenic proteins interact with membranes is a challenging task. Amyloid accumulates from many human diseases have been observed to contain membrane lipids. In this work, coarse-grained molecular dynamics simulations have been used to inspect hen egg white lysozyme (HEWL) aggregation and membrane association in the presence of a pure POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) bilayer and a POPC and POPG (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylglycerol) mixed bilayer. It was observed that, in both cases, two HEWLs formed aggregates. In the presence of a mixed bilayer, after aggregation, the aggregated system started to interact with the membrane. It has been found that one of the lysozymes which came closer to the mixed bilayer unfolded more. The process of the initial insertion of an aggregated system in the mixed bilayer has been analyzed. The structural rearrangements of the protein and lipids were analyzed as well along the course of the simulation. Although with a pure POPC bilayer, aggregation was observed, the aggregated system moved away from the membrane. We believe that our study will provide considerable insights into lysozyme aggregation in the presence of a membrane environment.
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Affiliation(s)
- Shahee Islam
- Department of Chemistry, University
of Calcutta, 92, A. P. C. Road, Kolkata 700009, India
| | - Chaitali Mukhopadhyay
- Department of Chemistry, University
of Calcutta, 92, A. P. C. Road, Kolkata 700009, India
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9
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Damian Guerrero E, Lopez-Velazquez AM, Ahlawat J, Narayan M. Carbon Quantum Dots for Treatment of Amyloid Disorders. ACS APPLIED NANO MATERIALS 2021; 4:2423-2433. [PMID: 33969279 PMCID: PMC8101282 DOI: 10.1021/acsanm.0c02792] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Prion-like amyloids self-template and form toxic oligomers, protofibrils, and fibrils from their soluble monomers; a phenomenon that has been implicated in the onset and progress of neurodegenerative disorders such as Alzheimer's (AD), Parkinson's (PD), Huntington's, and systemic lysozyme amyloidosis. Carbon quantum dots (CQDs), sourced from Na-citrate as a carbon precursor were synthesized and characterized before being tested for their ability to intervene in amyloidogenic (fibril-forming) trajectories. Hen-egg white lysozyme (HEWL) served as a model amyloidogenic protein. A pulse-chase lysozyme fibril-forming assay developed to examine the impact of CQDs on the HEWL amyloid-fibril-forming trajectory used ThT fluorescence as a reporter of mature fibril presence. The results revealed that the Na-citrate-derived CQDs were able to intervene at multiple points along the fibril-forming trajectory by preventing the conversion of both monomeric and oligomeric HEWL intermediates into mature fibrils. In addition, and importantly, the carbon nano material (CNM) was able to dissolve oligomeric HEWL into monomeric HEWL and provoke the disaggregation of mature HEWL fibrils. These results suggest that Na-citrate CQD's intervene in amyloidogenesis by multiple mechanisms. The gathered data, coupled with cell-line results demonstrating the relatively low cytotoxicity of Na-citrate CQDs, suggest that this emerging CNM has the potential to intervene both prophylactically and therapeutically in protein misfolding diseases. The aforementioned findings are likely to enable Na-citrate CQDs to eventually transition to both cell-line and preclinical models of protein-misfolding-related disorders. Importantly, the study outcomes positions Na-citrate CQDs as an important class of chemical, nanotechnological, and biobased interventional tools in neuroscience.
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Affiliation(s)
- Erick Damian Guerrero
- Department of Chemistry and Biochemistry, The University of Texas at El Paso (UTEP), El Paso, Texas 79968, United States
| | - Angela Marlene Lopez-Velazquez
- Department of Biological Sciences, Bioscience Research Building, Border Biomedical Research Center, the Cellular Characterization and Biorepository Core Facility, The University of Texas at El Paso (UTEP), El Paso, Texas 79968, United States
| | - Jyoti Ahlawat
- Department of Chemistry and Biochemistry, The University of Texas at El Paso (UTEP), El Paso, Texas 79968, United States
| | - Mahesh Narayan
- Department of Chemistry and Biochemistry, The University of Texas at El Paso (UTEP), El Paso, Texas 79968, United States
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10
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Mondal B, Nagesh J, Reddy G. Double Domain Swapping in Human γC and γD Crystallin Drives Early Stages of Aggregation. J Phys Chem B 2021; 125:1705-1715. [PMID: 33566611 DOI: 10.1021/acs.jpcb.0c07833] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Human γD (HγD) and γC (HγC) are two-domain crystallin (Crys) proteins expressed in the nucleus of the eye lens. Structural perturbations in the protein often trigger aggregation, which eventually leads to cataract. To decipher the underlying molecular mechanism, it is important to characterize the partially unfolded conformations, which are aggregation-prone. Using a coarse grained protein model and molecular dynamics simulations, we studied the role of on-pathway folding intermediates in the early stages of aggregation. The multidimensional free energy surface revealed at least three different folding pathways with the population of partially structured intermediates. The two dominant pathways confirm sequential folding of the N-terminal [Ntd] and the C-terminal domains [Ctd], while the third, least favored, pathway involves intermediates where both the domains are partially folded. A native-like intermediate (I*), featuring the folded domains and disrupted interdomain contacts, gets populated in all three pathways. I* forms domain swapped dimers by swapping the entire Ntds and Ctds with other monomers. Population of such oligomers can explain the increased resistance to unfolding resulting in hysteresis observed in the folding experiments of HγD Crys. An ensemble of double domain swapped dimers are also formed during refolding, where intermediates consisting of partially folded Ntds and Ctds swap secondary structures with other monomers. The double domain swapping model presented in our study provides structural insights into the early events of aggregation in Crys proteins and identifies the key secondary structural swapping elements, where introducing mutations will aid in regulating the overall aggregation propensity.
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Affiliation(s)
- Balaka Mondal
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India 560012
| | - Jayashree Nagesh
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India 560012
| | - Govardhan Reddy
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India 560012
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11
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Narayan M. Revisiting the Formation of a Native Disulfide Bond: Consequences for Protein Regeneration and Beyond. Molecules 2020; 25:molecules25225337. [PMID: 33207635 PMCID: PMC7697891 DOI: 10.3390/molecules25225337] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 11/12/2020] [Accepted: 11/13/2020] [Indexed: 11/16/2022] Open
Abstract
Oxidative protein folding involves the formation of disulfide bonds and the regeneration of native structure (N) from the fully reduced and unfolded protein (R). Oxidative protein folding studies have provided a wealth of information on underlying physico-chemical reactions by which disulfide-bond-containing proteins acquire their catalytically active form. Initially, we review key events underlying oxidative protein folding using bovine pancreatic ribonuclease A (RNase A), bovine pancreatic trypsin inhibitor (BPTI) and hen-egg white lysozyme (HEWL) as model disulfide bond-containing folders and discuss consequential outcomes with regard to their folding trajectories. We re-examine the findings from the same studies to underscore the importance of forming native disulfide bonds and generating a “native-like” structure early on in the oxidative folding pathway. The impact of both these features on the regeneration landscape are highlighted by comparing ideal, albeit hypothetical, regeneration scenarios with those wherein a native-like structure is formed relatively “late” in the R→N trajectory. A special case where the desired characteristics of oxidative folding trajectories can, nevertheless, stall folding is also discussed. The importance of these data from oxidative protein folding studies is projected onto outcomes, including their impact on the regeneration rate, yield, misfolding, misfolded-flux trafficking from the endoplasmic reticulum (ER) to the cytoplasm, and the onset of neurodegenerative disorders.
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Affiliation(s)
- Mahesh Narayan
- The Department of Chemistry and Biochemistry, The University of Texas as El Paso, El Paso, TX 79968, USA
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12
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Bhopatkar AA, Uversky VN, Rangachari V. Disorder and cysteines in proteins: A design for orchestration of conformational see-saw and modulatory functions. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2020; 174:331-373. [PMID: 32828470 DOI: 10.1016/bs.pmbts.2020.06.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Being responsible for more than 90% of cellular functions, protein molecules are workhorses in all the life forms. In order to cater for such a high demand, proteins have evolved to adopt diverse structures that allow them to perform myriad of functions. Beginning with the genetically directed amino acid sequence, the classical understanding of protein function involves adoption of hierarchically complex yet ordered structures. However, advances made over the last two decades have revealed that inasmuch as 50% of eukaryotic proteome exists as partially or fully disordered structures. Significance of such intrinsically disordered proteins (IDPs) is further realized from their ability to exhibit multifunctionality, a feature attributable to their conformational plasticity. Among the coded amino acids, cysteines are considered to be "order-promoting" due to their ability to form inter- or intramolecular disulfide bonds, which confer robust thermal stability to the protein structure in oxidizing conditions. The co-existence of order-promoting cysteines with disorder-promoting sequences seems counter-intuitive yet many proteins have evolved to contain such sequences. In this chapter, we review some of the known cysteine-containing protein domains categorized based on the number of cysteines they possess. We show that many protein domains contain disordered sequences interspersed with cysteines. We show that a positive correlation exists between the degree of cysteines and disorder within the sequences that flank them. Furthermore, based on the computational platform, IUPred2A, we show that cysteine-rich sequences display significant disorder in the reduced but not the oxidized form, increasing the potential for such sequences to function in a redox-sensitive manner. Overall, this chapter provides insights into an exquisite evolutionary design wherein disordered sequences with interspersed cysteines enable potential modulatory protein functions under stress and environmental conditions, which thus far remained largely inconspicuous.
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Affiliation(s)
- Anukool A Bhopatkar
- Department of Chemistry and Biochemistry, School of Mathematics and Natural Sciences, University of Southern Mississippi, Hattiesburg, MS, United States
| | - Vladimir N Uversky
- Department of Molecular Medicine and Byrd Alzheimer's Research Institute, Morsani College of Medicine, University of South Florida, Tampa, FL, United States; Laboratory of New Methods in Biology, Institute for Biological Instrumentation of the Russian Academy of Sciences, Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", Pushchino, Moscow Region, Russia
| | - Vijayaraghavan Rangachari
- Department of Chemistry and Biochemistry, School of Mathematics and Natural Sciences, University of Southern Mississippi, Hattiesburg, MS, United States; Center of Molecular and Cellular Biosciences, University of Southern Mississippi, Hattiesburg, MS, United States.
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13
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The Effect of Dimethyl Sulfoxide on the Lysozyme Unfolding Kinetics, Thermodynamics, and Mechanism. Biomolecules 2019; 9:biom9100547. [PMID: 31569484 PMCID: PMC6843525 DOI: 10.3390/biom9100547] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 09/26/2019] [Accepted: 09/27/2019] [Indexed: 02/07/2023] Open
Abstract
The thermal stability of proteins in the presence of organic solvents and the search for ways to increase this stability are important topics in industrial biocatalysis and protein engineering. The denaturation of hen egg-white lysozyme in mixtures of water with dimethyl sulfoxide (DMSO) with a broad range of compositions was studied using a combination of differential scanning calorimetry (DSC), circular dichroism (CD), and spectrofluorimetry techniques. In this study, for the first time, the kinetics of unfolding of lysozyme in DMSO–water mixtures was characterized. In the presence of DMSO, a sharp decrease in near-UV CD and an increase in the fluorescence signal were observed at lower temperatures than the DSC denaturation peak. It was found that differences in the temperatures of the CD and DSC signal changes increase as the content of DMSO increases. Changes in CD and fluorescence are triggered by a break of the tertiary contacts, leading to an intermediate state, while the DSC peak corresponds to a subsequent complete loss of the native structure. In this way, the commonly used two-state model was proven to be unsuitable to describe the unfolding of lysozyme in the presence of DMSO. In kinetic studies, it was found that even high concentrations of DMSO do not drastically change the activation energy of the initial stage of unfolding associated with a disruption of the tertiary structure, while the enthalpy of denaturation shows a significant dependence on DMSO content. This observation suggests that the structure of the transition state upon unfolding remains similar to the structure of the native state.
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