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Chi MC, Lu BY, Huang YF, Wang SW, Lin MG, Wang TF. Effects of Sodium Dodecyl Sulfate on the Enzyme Catalysis and Conformation of a Recombinant γ-Glutamyltranspeptidase from Bacillus licheniformis. Protein J 2023; 42:64-77. [PMID: 36739340 DOI: 10.1007/s10930-023-10095-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/30/2023] [Indexed: 02/06/2023]
Abstract
The study of interactions between proteins and surfactants is of relevance in a diverse range of applications including food, enzymatic detergent formulation, and drug delivery. In spite of sodium dodecyl sulfate (SDS)-induced unfolding has been studied in detail at the protein level, deciphering the conformation-activity relationship of a recombinant γ-glutamyltranspeptidase (BlrGGT) from Bacillus licheniformis remains important to understand how the transpeptidase activity is related to its conformation. In this study, we examined the enzyme catalysis and conformational transition of BlrGGT in the presence of SDS. Enzymatic assays showed that the transpeptidase activity of BlrGGT was greatly affected by SDS in a concentration-dependent manner with approximately 90% inactivation at 6 mM. Native polyacrylamide gel electrophoresis of SDS-treated samples clearly revealed that the heterodimeric enzyme was apparently dissociated into two different subunits at concentrations above 2 mM. The study of enzyme kinetics showed that SDS can act as a mixed-type inhibitor to reduce the catalytic efficiency of BlrGGT. Moreover, the t1/2 value of the enzyme at 55 °C was greatly reduced from 495.1 min to 7.4 min in the presence of 1 mM SDS. The I3/I1 ratio of pyrene excimer fluorescence emission changed around 3.7 mM SDS in the absence of BlrGGT and the inflection point of enzyme samples was reduced to less than 2.7 mM. The Far-UV CD spectrum of the native enzyme had two negative peaks at 208 and 222 nm, respectively; however, both negative peaks increased in magnitude with increasing SDS concentration and reached maximal values at above 4.0 mM. The intrinsic fluorescence spectra of tryptophan further demonstrated that the SDS-induced enzyme conformational transition occurred at approximately 5.1 mM. Tween 20 significantly suppressed the interaction of BlrGGT with SDS by forming mixed micelles at a molar ratio of 1.0. Taken together, this study definitely promotes our better understanding of the relationship between the conformation and catalysis of BlrGGT.
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Affiliation(s)
- Meng-Chun Chi
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan
| | - Bo-Yuan Lu
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan
| | - Yu-Fen Huang
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan
| | - Shih-Wei Wang
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan
| | - Min-Guan Lin
- Institute of Molecular Biology, Academia Sinica, Nangang District, Taipei City, 11529, Taiwan
| | - Tzu-Fan Wang
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan.
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Fatma I, Sharma V, Ahmad Malik N, Assad H, Cantero-López P, Sánchez J, López-Rendón R, Yañez O, Chand Thakur R, Kumar A. Influence of HSA on micellization of NLSS and BC: An experimental-theoretical approach of its binding characteristics. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.120532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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3
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Chemical-gas Sterilization of External Surface of Polymer-based Prefilled Syringes and Its Effect on Stability of Model Therapeutic Protein. J Pharm Sci 2021; 111:41-50. [PMID: 34499900 DOI: 10.1016/j.xphs.2021.09.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 09/02/2021] [Accepted: 09/02/2021] [Indexed: 11/22/2022]
Abstract
To reduce the risk of infection during intravitreal injections, the external surface of prefilled syringes (PFSs) must be sterilized. Usually, ethylene oxide (EO) gas or vaporized hydrogen peroxide (VHP) is used for sterilization. More recently, nitrogen dioxide (NO2) gas sterilization has been developed. It is known that gas permeability is approximately zero into glass-PFSs. However, polymer-PFSs (P-PFSs) have relatively high gas permeability. Therefore, there are concerns about the potential impact of external surface sterilization on drug solutions in P-PFSs. In this study, P-PFSs [filled with water for injection (WFI) or human serum albumin (HSA) solution] were externally sterilized using EO, VHP, and NO2 gases. For the WFI-filled syringes, the concentration of each gas that ingressed into the WFI was measured. For the HSA solution-filled syringes, the physical and chemical degradation of HSA molecules by each sterilant gas was quantified. For the EO- or VHP-sterilized syringes, the ingressed EO or hydrogen peroxide (H2O2) molecules were detected in the filled WFI. Additionally, EO-adducted or oxidized HSA molecules were observed in the HSA-filled syringes. In contrast, the NO2-sterilized WFI-filled syringes exhibited essentially immeasurable ingressed NO2, and protein degradation was not detected in HSA-filled syringes.
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Chelerythrine Chloride: A Potential Rumen Microbial Urease Inhibitor Screened by Targeting UreG. Int J Mol Sci 2021; 22:ijms22158212. [PMID: 34360977 PMCID: PMC8347364 DOI: 10.3390/ijms22158212] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 07/27/2021] [Accepted: 07/27/2021] [Indexed: 01/17/2023] Open
Abstract
Inhibition of ruminal microbial urease is of particular interest due to its crucial role in regulating urea-N utilization efficiency and nitrogen pollution in the livestock industry. Acetohydroxamic acid (AHA) is currently the only commercially available urease inhibitor, but it has adverse side effects. The urease accessory protein UreG, which facilitates the functional incorporation of the urease nickel metallocentre, has been proposed in developing urease inhibitor through disrupting urease maturation. The objective of this study was to screen natural compounds as potential urease inhibitors by targeting UreG in a predominant ruminal microbial urease. In silico screening and in vitro tests for potential inhibitors were performed using molecular docking and an assay for the GTPase activity of UreG. Chelerythrine chloride was selected as a potential urease inhibitor of UreG with an inhibition concentration IC50 value of 18.13 μM. It exhibited mixed inhibition, with the Ki value being 26.28 μM. We further explored its inhibition mechanism using isothermal titration calorimetry (ITC) and circular dichroism (CD) spectroscopy, and we found that chelerythrine chloride inhibited the binding of nickel to UreG and induced changes in the secondary structure, especially the α-helix and β-sheet of UreG. Chelerythrine chloride formed a pi-anion interaction with the Asp41 residue of UreG, which is an important residue in initiating the conformational changes of UreG. In conclusion, chelerythrine chloride exhibited a potential inhibitory effect on urease, which provided new evidence for strategies to develop novel urease inhibitors targeting UreG to reduce nitrogen excretion from ruminants.
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Unveiling the thermodynamic signature underlying the interaction of human serum albumin with sub-micellar concentrations of a surface active ionic liquid. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.114078] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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6
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Samant V, Dey A, Naresh Patwari G. Probing the interaction between human serum albumin and the sodium dodecyl sulphate with fluorescence correlation spectroscopy. J CHEM SCI 2020. [DOI: 10.1007/s12039-020-01816-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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7
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Modi R, Khamari L, Nandy A, Mukherjee S. Spectroscopic probing of the refolding of an unfolded protein through the formation of mixed-micelles. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2019; 216:52-60. [PMID: 30878845 DOI: 10.1016/j.saa.2019.03.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 02/17/2019] [Accepted: 03/04/2019] [Indexed: 06/09/2023]
Abstract
We report the unfolding of the globular protein, Bovine Serum Albumin (BSA) induced by anionic surfactant sodium dodecyl sulfate (SDS) and subsequently monitored the refolding of this denatured BSA using triblock copolymers F127 and P123 through the formation of mixed micelles. Our study exclusively represents the reversibility of this unfolding-refolding process using pluronic triblock copolymers F127/P123 as refolding agents. We confirm the recovery of its native state from its denatured state estimating the α-helical structure of the denatured protein from the CD data which support our steady state fluorescence spectra monitoring the fluorescence of the intrinsic Trp molecules present in BSA. Time resolved study also corroborates the stepwise recovery of the denatured BSA as well as the reversibility of the processes. Isothermal Titration Calorimetry (ITC) data explain the negligible interactions between the triblock copolymers and the native state of BSA. The high binding constant of SDS and triblock copolymers probably play the crucial role in the stepwise recovery of the unfolded BSA followed by reversibility of the refolding processes through the formation of the mixed micelles. The mechanism of mixed-micelle formation has been substantiated by the fact that the Guanidine Hydrochloride denatured BSA does not react with F127/P123 whereby no recovery of the protein was observed.
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Affiliation(s)
- Riya Modi
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhauri, Bhopal 426 066, Madhya Pradesh, India
| | - Laxmikanta Khamari
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhauri, Bhopal 426 066, Madhya Pradesh, India
| | - Atanu Nandy
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhauri, Bhopal 426 066, Madhya Pradesh, India
| | - Saptarshi Mukherjee
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhauri, Bhopal 426 066, Madhya Pradesh, India.
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Vanilla bahiana, a contribution from the Atlantic Forest biodiversity for the production of vanilla: A proteomic approach through high-definition nanoLC/MS. Food Res Int 2019; 120:148-156. [PMID: 31000225 DOI: 10.1016/j.foodres.2019.02.038] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 02/16/2019] [Accepted: 02/19/2019] [Indexed: 11/22/2022]
Abstract
Only a few cultivated species of Vanilla are used to produce vanilla, despite the high demand, predatory exploitation, and low genetic variability that threaten the production of natural vanilla. Vanilla bahiana pods from the Atlantic Forest may be an alternative source of natural vanilla. This study applied bottom-up and shotgun proteomics analysis to identify proteins related to flowering, fruiting, and vanilla-flavor production. Extraction solutions, including Tris-HCl buffer, β-mercaptoethanol and SDS, were assayed. SDS proved to be feasible for extraction of Vanilla fruit proteins and could be an alternative to the phenol method of protein extraction. Progenesis QI for Proteomics (QIP) software loaded with an Orchidaceae database identified 2326 proteins in our samples. Among these, 75 were highlighted as useful for the synthesis of compounds related to vanilla flavor, such as vanillin synthase, which was successfully extracted with 1% SDS, which also improved the variety of the extracted proteins. The proteins identified in V. bahiana pods indicate the enzymatic potential of this species, as further validated by quantifying the vanilla in the samples.
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Ma L, Xu J, Chen N, Li M, Feng C. Microbial reduction fate of chromium (Cr) in aqueous solution by mixed bacterial consortium. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2019; 170:763-770. [PMID: 30583287 DOI: 10.1016/j.ecoenv.2018.12.041] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Revised: 12/14/2018] [Accepted: 12/15/2018] [Indexed: 06/09/2023]
Abstract
Groundwater contaminated by Cr(VI) requires effective remediation to prevent adverse environmental impacts. The biodegradation of Cr(VI) has been documented for several decades, but little remains known about the removal fate of chromium, including the main species of reductase (sites) and functional genes involved in Cr(VI) reduction in mixed bacterial consortium. Cr(VI) reduction in this study was verified to be an enzyme-mediated process. Meanwhile, Cr(VI) reduction of different cell components demonstrated that the extracellular enzyme was the main active substance, and the distribution of Cr after experiment was quantified using mass balance calculation. Furthermore, the optimal pH for reduction was 8.0, with the reduction rate decreasing with increasing initial Cr(VI) concentrations. The co-existing oxyanions had little effect on Cr(VI) reduction, while the presence of other heavy metals had a relatively significant influence. The evolutionary behavior of microbial community structure and functional genes affected by Cr(VI) were also analyzed, which provided new insights on the underlying mechanisms involved in bioreduction in this study. These results generated new understanding of the reduction mechanisms on the Cr-relevant bacterial species and genes, which would be helpful in designing strategies for the bioremediation of Cr(VI) contaminated water.
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Affiliation(s)
- Linlin Ma
- School of Water Resources and Environment, MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing 100083, PR China
| | - Jinming Xu
- School of Sciences, China University of Geosciences (Beijing), Beijing 100083, PR China
| | - Nan Chen
- School of Water Resources and Environment, MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing 100083, PR China.
| | - Miao Li
- School of Environment, Tsinghua University, Beijing 100084, PR China
| | - Chuanping Feng
- School of Water Resources and Environment, MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing 100083, PR China
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Huda N, Hossain M, Bhuyan AK. Complete observation of all structural, conformational, and fibrillation transitions of monomeric globular proteins at submicellar sodium dodecyl sulfate concentrations. Biopolymers 2019; 110:e23255. [PMID: 30633322 DOI: 10.1002/bip.23255] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 12/18/2018] [Accepted: 12/21/2018] [Indexed: 11/06/2022]
Abstract
Although considerable information is available regarding protein-sodium dodecyl sulfate (SDS) interactions, it is still unclear as to how much SDS is needed to denature proteins. The role of protein charge and micellar surfactant concentration on amyloid fibrillation is also unclear. This study reports on equilibrium measurements of SDS interaction with six model proteins and analyzes the results to obtain a general understanding of conformational breakdown, reorganization and restructuring of secondary structure, and entry into the amyloid fibrillar state. Significantly, all of these responses are entirely resolved at much lower than the critical micellar concentration (CMC) of SDS. Electrostatic interaction of the dodecyl sulfate anion (DS- ) with positive surface potential on the protein can completely unfold both secondary and tertiary structures, which is followed by protein chain restructuration to α-helices. All SDS-denatured proteins contain more α-helices than the corresponding native state. SDS interaction stochastically drives proteins to the aggregated fibrillar state.
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Affiliation(s)
- Noorul Huda
- School of Chemistry, University of Hyderabad, Hyderabad, India
| | - Mujahid Hossain
- School of Chemistry, University of Hyderabad, Hyderabad, India
| | - Abani K Bhuyan
- School of Chemistry, University of Hyderabad, Hyderabad, India
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11
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Scavenging of hydrated electron by HSA or Ligand/HSA adduct: Pulse radiolysis study. Radiat Phys Chem Oxf Engl 1993 2018. [DOI: 10.1016/j.radphyschem.2018.07.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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12
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Siaw HMH, Raghunath G, Dyer RB. Peripheral Protein Unfolding Drives Membrane Bending. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:8400-8407. [PMID: 29925237 PMCID: PMC6069603 DOI: 10.1021/acs.langmuir.8b01136] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Dynamic modulation of lipid membrane curvature can be achieved by a number of peripheral protein binding mechanisms such as hydrophobic insertion of amphipathic helices and membrane scaffolding. Recently, an alternative mechanism was proposed in which crowding of peripherally bound proteins induces membrane curvature through steric pressure generated by lateral collisions. This effect was enhanced using intrinsically disordered proteins that possess high hydrodynamic radii, prompting us to explore whether membrane bending can be triggered by the folding-unfolding transition of surface-bound proteins. We utilized histidine-tagged human serum albumin bound to Ni-NTA-DGS containing liposomes as our model system to test this hypothesis. We found that reduction of the disulfide bonds in the protein resulted in unfolding of HSA, which subsequently led to membrane tubule formation. The frequency of tubule formation was found to be significantly higher when the proteins were unfolded while being localized to a phase-separated domain as opposed to randomly distributed in fluid phase liposomes, indicating that the steric pressure generated from protein unfolding can drive membrane deformation. Our results are critical for the design of peripheral membrane protein-immobilization strategies and open new avenues for exploring mechanisms of membrane bending driven by conformational changes of peripheral membrane proteins.
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Andersen KK, Vad BS, Kjær L, Tolker‐Nielsen T, Christiansen G, Otzen DE. Pseudomonas aeruginosa
rhamnolipid induces fibrillation of human α‐synuclein and modulates its effect on biofilm formation. FEBS Lett 2018; 592:1484-1496. [DOI: 10.1002/1873-3468.13038] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Revised: 02/21/2018] [Accepted: 03/12/2018] [Indexed: 01/20/2023]
Affiliation(s)
- Kell K. Andersen
- Interdisciplinary Nanoscience Center (iNANO) Department of Molecular Biology and Genetics Aarhus University Denmark
| | - Brian S. Vad
- Interdisciplinary Nanoscience Center (iNANO) Department of Molecular Biology and Genetics Aarhus University Denmark
| | - Lars Kjær
- Interdisciplinary Nanoscience Center (iNANO) Department of Molecular Biology and Genetics Aarhus University Denmark
| | - Tim Tolker‐Nielsen
- Costerton Biofilm Center Department of Immunology and Microbiology University of Copenhagen Denmark
| | | | - Daniel E. Otzen
- Interdisciplinary Nanoscience Center (iNANO) Department of Molecular Biology and Genetics Aarhus University Denmark
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14
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Jafari M, Mehrnejad F, Rahimi F, Asghari SM. The Molecular Basis of the Sodium Dodecyl Sulfate Effect on Human Ubiquitin Structure: A Molecular Dynamics Simulation Study. Sci Rep 2018; 8:2150. [PMID: 29391595 PMCID: PMC5794983 DOI: 10.1038/s41598-018-20669-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Accepted: 01/16/2018] [Indexed: 01/01/2023] Open
Abstract
To investigate the molecular interactions of sodium dodecyl sulfate (SDS) with human ubiquitin and its unfolding mechanisms, a comparative study was conducted on the interactions of the protein in the presence and absence of SDS at different temperatures using six independent 500 ns atomistic molecular dynamics (MD) simulations. Moreover, the effects of partial atomic charges on SDS aggregation and micellar structures were investigated at high SDS concentrations. The results demonstrated that human ubiquitin retains its native-like structure in the presence of SDS and pure water at 300 K, while the conformation adopts an unfolded state at a high temperature. In addition, it was found that both SDS self-assembly and the conformation of the resulting protein may have a significant effect of reducing the partial atomic charges. The simulations at 370 K provided evidence that the SDS molecules disrupted the first hydration shell and expanded the hydrophobic core of ubiquitin, resulting in complete protein unfolding. According to these results, SDS and temperature are both required to induce a completely unfolded state under ambient conditions. We believe that these findings could be useful in protein folding/unfolding studies and structural biology.
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Affiliation(s)
- Majid Jafari
- Nanobiotechnology Lab, Department of Life Sciences Engineering, Faculty of New Sciences and Technologies, University of Tehran, 14395-1561, Tehran, Iran
| | - Faramarz Mehrnejad
- Nanobiotechnology Lab, Department of Life Sciences Engineering, Faculty of New Sciences and Technologies, University of Tehran, 14395-1561, Tehran, Iran.
| | - Fereshteh Rahimi
- Nanobiotechnology Lab, Department of Life Sciences Engineering, Faculty of New Sciences and Technologies, University of Tehran, 14395-1561, Tehran, Iran
| | - S Mohsen Asghari
- Department of Biology, Faculty of Sciences, University of Guilan, 4193833697, Rasht, Iran
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Paul BK, Sett R, Guchhait N. Stepwise unfolding of Ribonuclease A by a biosurfactant. J Colloid Interface Sci 2017; 505:673-681. [DOI: 10.1016/j.jcis.2017.06.051] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 06/16/2017] [Accepted: 06/16/2017] [Indexed: 11/29/2022]
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Kaspersen JD, Søndergaard A, Madsen DJ, Otzen DE, Pedersen JS. Refolding of SDS-Unfolded Proteins by Nonionic Surfactants. Biophys J 2017; 112:1609-1620. [PMID: 28445752 PMCID: PMC5406375 DOI: 10.1016/j.bpj.2017.03.013] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 03/03/2017] [Accepted: 03/07/2017] [Indexed: 11/30/2022] Open
Abstract
The strong and usually denaturing interaction between anionic surfactants (AS) and proteins/enzymes has both benefits and drawbacks: for example, it is put to good use in electrophoretic mass determinations but limits enzyme efficiency in detergent formulations. Therefore, studies of the interactions between proteins and AS as well as nonionic surfactants (NIS) are of both basic and applied relevance. The AS sodium dodecyl sulfate (SDS) denatures and unfolds globular proteins under most conditions. In contrast, NIS such as octaethylene glycol monododecyl ether (C12E8) and dodecyl maltoside (DDM) protect bovine serum albumin (BSA) from unfolding in SDS. Membrane proteins denatured in SDS can also be refolded by addition of NIS. Here, we investigate whether globular proteins unfolded by SDS can be refolded upon addition of C12E8 and DDM. Four proteins, BSA, α-lactalbumin (αLA), lysozyme, and β-lactoglobulin (βLG), were studied by small-angle x-ray scattering and both near- and far-UV circular dichroism. All proteins and their complexes with SDS were attempted to be refolded by the addition of C12E8, while DDM was additionally added to SDS-denatured αLA and βLG. Except for αLA, the proteins did not interact with NIS alone. For all proteins, the addition of NIS to the protein-SDS samples resulted in extraction of the SDS from the protein-SDS complexes and refolding of βLG, BSA, and lysozyme, while αLA changed to its NIS-bound state instead of the native state. We conclude that NIS competes with globular proteins for association with SDS, making it possible to release and refold SDS-denatured proteins by adding sufficient amounts of NIS, unless the protein also interacts with NIS alone.
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Affiliation(s)
| | | | - Daniel Jhaf Madsen
- Interdisciplinary Nanoscience Centre (iNANO), Aarhus University, Aarhus, Denmark
| | - Daniel E Otzen
- Interdisciplinary Nanoscience Centre (iNANO), Aarhus University, Aarhus, Denmark.
| | - Jan Skov Pedersen
- Interdisciplinary Nanoscience Centre (iNANO), Aarhus University, Aarhus, Denmark; Department of Chemistry, Aarhus University, Aarhus, Denmark.
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