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Ansari NK, Khan HS, Naeem A. Doxorubicin as a Drug Repurposing for Disruption of α-Chymotrypsinogen-A Aggregates. Protein J 2024:10.1007/s10930-024-10217-w. [PMID: 39014260 DOI: 10.1007/s10930-024-10217-w] [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: 06/20/2024] [Indexed: 07/18/2024]
Abstract
Protein conformation is affected by interaction of several small molecules resulting either stabilization or disruption depending on the nature of the molecules. In our earlier communication, Hg2+ was known to disrupt the native structure of α-Cgn A leading to aggregation (Ansari, N.K., Rais, A. & Naeem, A. Methotrexate for Drug Repurposing as an Anti-Aggregatory Agent to Mercuric Treated α-Chymotrypsinogen-A. Protein J (2024). https://doi.org/10.1007/s10930-024-10187-z ). Accumulation of β-rich aggregates in the living system is found to be linked with copious number of disorders. Here, we have investigated the effect of varying concentration of doxorubicin (DOX) i.e. 0-100 µM on the preformed aggregates of α-Cgn A upon incubation with 120 µM Hg2+. The decrease in the intrinsic fluorescence and enzyme activity with respect to increase in the Hg2+ concentration substantiate the formation of aggregates. The DOX showed the dose dependent decrease in the ThT fluorescence, turbidity and RLS measurements endorsing the dissolution of aggregates which were consistent with red shift in ANS, confirming the breakdown of aggregates. The α-Cgn A has 30% α-helical content which decreases to 3% in presence of Hg2+. DOX increased the α-helicity to 28% confirming its anti-aggregatory potential. The SEM validates the formation of aggregates with Hg2+ and their dissolution upon incubation with the DOX. Hemolysis assay checked the cytotoxicity of α-Cgn A aggregates. Docking revealed that the DOX interacted Lys203, Cys201, Cys136, Ser159, Leu10, Trp207, Val137 and Thr134 of α-Cgn A through hydrophobic interactions and Gly133, Thr135 and Lys202 forms hydrogen bonds.
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Affiliation(s)
- Neha Kausar Ansari
- Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh, U.P, 202002, India
| | - Hamza Sahib Khan
- Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh, U.P, 202002, India
| | - Aabgeena Naeem
- Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh, U.P, 202002, India.
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MacKeigan TP, Morgan ML, Stys PK. Quantitation of Tissue Amyloid via Fluorescence Spectroscopy Using Controlled Concentrations of Thioflavin-S. Molecules 2023; 28:molecules28114483. [PMID: 37298959 DOI: 10.3390/molecules28114483] [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: 05/04/2023] [Revised: 05/24/2023] [Accepted: 05/29/2023] [Indexed: 06/12/2023] Open
Abstract
Amyloids are misfolded proteins that aggregate into fibrillar structures, the accumulation of which is associated with the pathogenesis of many neurodegenerative diseases, such as Alzheimer's disease (AD). Early, sensitive detection of these misfolded aggregates is of great interest to the field, as amyloid deposition begins well before the presentation of clinical symptoms. Thioflavin-S (ThS) is a fluorescent probe commonly used to detect amyloid pathology. Protocols for ThS staining vary, but they often use high staining concentrations followed by differentiation, which causes varying levels of non-specific staining and potentially leaves more subtle amyloid deposition unidentified. In this study, we developed an optimized ThS staining protocol for the sensitive detection of β-amyloids in the widely used 5xFAD Alzheimer's mouse model. Controlled dye concentrations together with fluorescence spectroscopy and advanced analytical methods enabled not only the visualization of plaque pathology, but also the detection of subtle and widespread protein misfolding throughout the 5xFAD white matter and greater parenchyma. Together, these findings demonstrate the efficacy of a controlled ThS staining protocol and highlight the potential use of ThS for the detection of protein misfolding that precedes clinical manifestation of disease.
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Affiliation(s)
- Tatiana P MacKeigan
- Department of Clinical Neurosciences, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
| | - Megan L Morgan
- Department of Clinical Neurosciences, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
| | - Peter K Stys
- Department of Clinical Neurosciences, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
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Mendoza R, Ferrer-Miralles N, Corchero JL. Eukaryotic Aggresomes: Protocols and Tips for Their Production, Purification , and Handling. Methods Mol Biol 2022; 2406:417-435. [PMID: 35089572 DOI: 10.1007/978-1-0716-1859-2_25] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Aggresomes are insoluble protein aggregates found in eukaryotic cells when the intracellular machinery is overtitered by, for example, the overexpression of a recombinant protein. These protein nanoparticles have become excellent models in studies devoted to elucidate protein aggregation processes in eukaryotic cells, like those involved in "conformational disorders" linked to neurodegenerative diseases. Since the presence of such protein aggregates is a hallmark of these conditions, they constitute an excellent target for new therapeutic approaches for such devastating pathologies. Moreover, and following the pathway opened a few years ago by bacterial inclusion bodies, eukaryotic aggresomes have been proposed as a new type of carrier-free, self-immobilized biocatalysts for use in biotechnology and biomedicine. Altogether, unraveling the characteristics and putative applications of naturally occurring protein aggregates has received an increasing interest during the last years. For that, availability of protocols allowing the production and purification of aggresomes constitute a valuable tool to boost research in the abovementioned fields. In this chapter, we describe both upstream and downstream protocols to obtain aggresomes produced in human cells, using as a model the recombinant human enzyme alpha-galactosidase A (GLA), together with technical tips and advices when working and analyzing eukaryotic aggresomes.
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Affiliation(s)
- Rosa Mendoza
- CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Barcelona, Spain
- Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
| | - Neus Ferrer-Miralles
- CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Barcelona, Spain
- Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
| | - José Luis Corchero
- CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Barcelona, Spain.
- Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain.
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain.
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Banerjee S. Effect of glyoxal and 1-methylisatin on stress-induced fibrillation of Hen Egg White Lysozyme: Insight into the anti-amyloidogenic property of the compounds with possible therapeutic implications. Int J Biol Macromol 2020; 165:1552-1561. [DOI: 10.1016/j.ijbiomac.2020.10.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Revised: 09/26/2020] [Accepted: 10/02/2020] [Indexed: 10/23/2022]
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Varela AE, England KA, Cavagnero S. Kinetic trapping in protein folding. Protein Eng Des Sel 2020; 32:103-108. [PMID: 31390019 DOI: 10.1093/protein/gzz018] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 07/03/2019] [Indexed: 12/31/2022] Open
Abstract
The founding principles of protein folding introduced by Christian Anfinsen, together with the numerous mechanistic investigations that followed, assume that protein folding is a thermodynamically controlled process. On the other hand, this review underscores the fact that thermodynamic control is far from being the norm in protein folding, as long as one considers an extended chemical-potential landscape encompassing aggregates, in addition to native, unfolded and intermediate states. Here, we highlight the key role of kinetic trapping of the protein native state relative to unfolded, intermediate and, most importantly, aggregated states. We propose that kinetic trapping serves an important role in biology by protecting the bioactive states of a large number of proteins from deleterious aggregation. In the event that undesired aggregates were somehow formed, specialized intracellular disaggregation machines have evolved to convert any aberrant populations back to the native state, thus restoring a fully bioactive and aggregation-protected protein cohort.
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Affiliation(s)
- Angela E Varela
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Kevin A England
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Silvia Cavagnero
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
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Li S, Chen W, Hu X, Feng F. Self-Assembly of Albumin and [FeFe]-Hydrogenase Mimics for Photocatalytic Hydrogen Evolution. ACS APPLIED BIO MATERIALS 2020; 3:2482-2488. [DOI: 10.1021/acsabm.0c00194] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Shuyi Li
- Key Laboratory of High Performance Polymer Material and Technology of Ministry of Education, Department of Polymer Science & Engineering, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Weijian Chen
- Key Laboratory of High Performance Polymer Material and Technology of Ministry of Education, Department of Polymer Science & Engineering, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Xiantao Hu
- Key Laboratory of High Performance Polymer Material and Technology of Ministry of Education, Department of Polymer Science & Engineering, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Fude Feng
- Key Laboratory of High Performance Polymer Material and Technology of Ministry of Education, Department of Polymer Science & Engineering, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing 210023, China
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Abidar S, Yildiz O, Degirmenci A, Amakran A, El Maadoudi M, Nhiri M. Glucose-mediated protein glycation: Contribution of methanolic extract of Ceratonia siliqua L. in protection and in vitro potential inhibition of acetylcholinesterase. J Food Biochem 2019; 43:e13009. [PMID: 31393019 DOI: 10.1111/jfbc.13009] [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: 05/10/2019] [Revised: 07/02/2019] [Accepted: 07/12/2019] [Indexed: 01/11/2023]
Abstract
Chronic hyperglycemia presents the major etiology of diabetes mellitus and related complications mainly Alzheimer's disease, via the protein glycation and toxic products generated. In the current study, we investigated the eventual protective effect of the methanolic extract of Ceratonia siliqua L. (CsME) against glucose-mediated glycation in serum bovine albumin. The multi-stage glycation markers, namely fructosamines and advanced glycation end products (AGEs) levels were monitored along with measurement of thiol groups; moreover, the in vitro acetylcholinesterase (AChE) inhibition potential was carried out. HPLC was also assessed. Rutin was the main phenolic compound found in CsME. CsME showed a good capacity to inhibit AGEs, fructosamines and protected thiol groups against glycation. CsME exhibited a great AChE inhibition activity. In the present study, CsME prevented glucose-induced protein glycation, it also exhibited a good inhibition of AChE, suggesting its DM complications such as memory troubles related to AD. PRACTICAL APPLICATIONS: Neurodegenerative disorders ranging from memory troubles to Alzheimer's disease present the most diabetes mellitus complications and mainly attributed to protein glycation process. Currently, there is a strong trend to search for efficient natural sources of glycation and acetylcholinesterase inhibitors to replace the synthetic ones, whose secondary effects were shown. The present article tries to justify scientifically the wide use of Ceratonia siliqua L. in Moroccan folk medicine, demonstrating that the methanolic extract of leaves from this species presents a promising source of new natural compounds inhibiting acetylcholinesterase and acting in vitro against glycation generated compounds. Furthermore, for the first time, Rutin was the main phenolic compound found in this extract, these encouraging results should be coupled with further studies to integrate it in pharmaceutical formulations. As such, this paper should be of interest to a broad readership, including those interested in Biochemistry, Phytochemistry, pharmacology, and neurosciences.
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Affiliation(s)
- Sara Abidar
- Laboratoire de Biochimie et Génétique Moléculaire, Faculté des Sciences et Techniques, Université Abdelmalek Essaâdi, Tanger Principal, Morocco
| | - Oktay Yildiz
- Maçka VHS, Department of Food Processing, Karadeniz Technical University, Trabzon, Turkey
| | - Atiye Degirmenci
- Maçka VHS, Department of Food Processing, Karadeniz Technical University, Trabzon, Turkey
| | - Amina Amakran
- Laboratoire de Biochimie et Génétique Moléculaire, Faculté des Sciences et Techniques, Université Abdelmalek Essaâdi, Tanger Principal, Morocco
| | - Mohammed El Maadoudi
- Laboratoire Régional d'Analyses et de Recherches de l'ONSSA (office national de sécurité sanitaire des produits alimentaires), Tanger, Maroc
| | - Mohamed Nhiri
- Laboratoire de Biochimie et Génétique Moléculaire, Faculté des Sciences et Techniques, Université Abdelmalek Essaâdi, Tanger Principal, Morocco
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8
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Hasan S, Fatma S, Zaman M, Khan RH, Naeem A. Carboxylic acids of different nature induces aggregation of hemoglobin. Int J Biol Macromol 2018; 118:1584-1593. [DOI: 10.1016/j.ijbiomac.2018.07.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Revised: 07/01/2018] [Accepted: 07/02/2018] [Indexed: 01/28/2023]
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9
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Sohail A, Bhat WF, Bhat SA, Furkan M, Shah A, Bano B. Investigating the preventive effects of baicalin and gallocatechin against glyoxal-induced cystatin aggregation. J Biomol Struct Dyn 2017; 36:3791-3802. [PMID: 29143574 DOI: 10.1080/07391102.2017.1400470] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Several mammalian proteins form pathological deposits under nonphysiological conditions that are associated with many degenerative diseases. Protein aggregation is associated with aging, as well as a variety of diseases, including cystic fibrosis, amyotrophic lateral sclerosis (ALS), and hypertrophic cardiomyopathy. There is a lack of any potential anti-amyloidogenic agents and therapeutics till date. Polyphenols have been accredited with myriad biological effects. An analysis of the effects of natural agents like baicalin (BC) and gallocatechin (GC) on aggregation process can open new avenues for the treatment of protein misfolding diseases. Thus, investigation of the effects of these flavonoids on Buffalo Heart Cystatin (BHC) aggregation induced by a reactive metabolic dialdehyde, glyoxal (GO), was taken up. Results have shown that elevated concentration of GO forms aggregates of BHC, which was characterized by an increase in the ANS fluorescence intensity, an increase in ThT fluorescence intensity, red shift in Congo red absorbance, negative ellipticity peak at 217 nm in the far-UVCD and BHC aggregates displaying by TEM. Using fluorescence spectroscopic analysis with Thioflavin T, CD and electron microscopic studies, anti-aggregation effects of polyphenols, BC and GC were analyzed. The study showed that BC and GC produced concentration-dependent anti-aggregation effects with GC producing a more pronounced effect than BC. The study proposed a mechanistic approach assuming structural constraints and specific aromatic interactions of polyphenols with sheets of BHC aggregates.
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Affiliation(s)
- Aamir Sohail
- a Department of Biochemistry, Faculty of Life Sciences , Aligarh Muslim University , Aligarh , UP 202002 , India
| | - Waseem Feeroze Bhat
- a Department of Biochemistry, Faculty of Life Sciences , Aligarh Muslim University , Aligarh , UP 202002 , India
| | - Sheraz Ahmad Bhat
- a Department of Biochemistry, Faculty of Life Sciences , Aligarh Muslim University , Aligarh , UP 202002 , India
| | - Mohammad Furkan
- a Department of Biochemistry, Faculty of Life Sciences , Aligarh Muslim University , Aligarh , UP 202002 , India
| | - Aaliya Shah
- b Department of Biochemistry , SKIMS Medical College , Srinagar , Jammu and Kashmir , India
| | - Bilqees Bano
- a Department of Biochemistry, Faculty of Life Sciences , Aligarh Muslim University , Aligarh , UP 202002 , India
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10
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Islam S, Moinuddin, Mir AR, Raghav A, Habib S, Alam K, Ali A. Glycation, oxidation and glycoxidation of IgG: a biophysical, biochemical, immunological and hematological study. J Biomol Struct Dyn 2017; 36:2637-2653. [DOI: 10.1080/07391102.2017.1365770] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Sidra Islam
- Department of Biochemistry, Jawarharlal Nehru Medical College, Faculty of Medicine, Aligarh Muslim University, Aligarh 202002, Uttar Pradesh, India
| | - Moinuddin
- Department of Biochemistry, Jawarharlal Nehru Medical College, Faculty of Medicine, Aligarh Muslim University, Aligarh 202002, Uttar Pradesh, India
| | - Abdul Rouf Mir
- Department of Biochemistry, Jawarharlal Nehru Medical College, Faculty of Medicine, Aligarh Muslim University, Aligarh 202002, Uttar Pradesh, India
- Department of Biotechnology, Government Degree College, University of Kashmir, Baramulla 193101, Jammu and Kashmir, India
| | - Alok Raghav
- Rajiv Gandhi Centre for Diabetes and Endocrinology, Aligarh Muslim University, Aligarh 202002, Uttar Pradesh, India
| | - Safia Habib
- Department of Biochemistry, Jawarharlal Nehru Medical College, Faculty of Medicine, Aligarh Muslim University, Aligarh 202002, Uttar Pradesh, India
| | - Khursheed Alam
- Department of Biochemistry, Jawarharlal Nehru Medical College, Faculty of Medicine, Aligarh Muslim University, Aligarh 202002, Uttar Pradesh, India
| | - Asif Ali
- Department of Biochemistry, Jawarharlal Nehru Medical College, Faculty of Medicine, Aligarh Muslim University, Aligarh 202002, Uttar Pradesh, India
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11
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Roskamp KW, Montelongo DM, Anorma CD, Bandak DN, Chua JA, Malecha KT, Martin RW. Multiple Aggregation Pathways in Human γS-Crystallin and Its Aggregation-Prone G18V Variant. Invest Ophthalmol Vis Sci 2017; 58:2397-2405. [PMID: 28444328 PMCID: PMC5407245 DOI: 10.1167/iovs.16-20621] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Purpose Cataract results from the formation of light-scattering precipitates due to point mutations or accumulated damage in the structural crystallins of the eye lens. Although excised cataracts are predominantly amorphous, in vitro studies show that crystallins are capable of adopting a variety of morphologies depending on the preparation method. Here we characterize thermal, pH-dependent, and UV-irradiated aggregates from wild-type human γS-crystallin (γS-WT) and its aggregation-prone variant, γS-G18V. Methods Aggregates of γS-WT and γS-G18V were prepared under acidic, neutral, and basic pH conditions and held at 25°C or 37°C for 48 hours. UV-induced aggregates were produced by irradiation with a 355-nm laser. Aggregation and fibril formation were monitored via turbidity and thioflavin T (ThT) assays. Aggregates were characterized using intrinsic aromatic fluorescence, powder x-ray diffraction, and mass spectrometry. Results γS-crystallin aggregates displayed different characteristics depending on the preparation method. γS-G18V produced a larger amount of detectable aggregates than did γS-WT and at less-extreme conditions. Aggregates formed under basic and acidic conditions yielded elevated ThT fluorescence; however, aggregates formed at low pH did not produce strongly turbid solutions. UV-induced aggregates produced highly turbid solutions but displayed only moderate ThT fluorescence. X-ray diffraction confirms amyloid character in low-pH samples and UV-irradiated samples, although the relative amounts vary. Conclusions γS-G18V demonstrates increased aggregation propensity compared to γS-WT when treated with heat, acid, or UV light. The resulting aggregates differ in their ThT fluorescence and turbidity, suggesting that at least two different aggregation pathways are accessible to both proteins under the conditions tested.
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Affiliation(s)
- Kyle W Roskamp
- Department of Chemistry, University of California, Irvine, Irvine, California, United States
| | - David M Montelongo
- Department of Chemistry, University of California, Irvine, Irvine, California, United States
| | - Chelsea D Anorma
- Department of Chemistry, University of California, Irvine, Irvine, California, United States
| | - Diana N Bandak
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, California, United States
| | - Janine A Chua
- Department of Chemistry, University of California, Irvine, Irvine, California, United States
| | - Kurtis T Malecha
- Department of Chemistry, University of California, Irvine, Irvine, California, United States
| | - Rachel W Martin
- Department of Chemistry, University of California, Irvine, Irvine, California, United States 2Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, California, United States
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12
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Secondary structural alterations in glucoamylase as an influence of protein aggregation. Int J Biol Macromol 2017; 98:459-468. [DOI: 10.1016/j.ijbiomac.2017.01.086] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 01/15/2017] [Accepted: 01/18/2017] [Indexed: 11/21/2022]
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13
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Furkan M, Rizvi A, Alam MT, Naeem A. Peroxidase improves the activity of catalase by preventing aggregation during TFE-induced denaturation. J Biomol Struct Dyn 2017; 36:551-560. [DOI: 10.1080/07391102.2017.1287007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Mohammad Furkan
- Faculty of Life Sciences, Department of Biochemistry, Aligarh Muslim University, Aligarh 202002, India
| | - Asim Rizvi
- Faculty of Life Sciences, Department of Biochemistry, Aligarh Muslim University, Aligarh 202002, India
| | - Md Tauqir Alam
- Faculty of Life Sciences, Department of Biochemistry, Aligarh Muslim University, Aligarh 202002, India
| | - Aabgeena Naeem
- Faculty of Life Sciences, Department of Biochemistry, Aligarh Muslim University, Aligarh 202002, India
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14
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Awasthi M, Singh S, Pandey VP, Dwivedi UN. Modulation in the conformational and stability attributes of the Alzheimer's disease associated amyloid-beta mutants and their favorable stabilization by curcumin: molecular dynamics simulation analysis. J Biomol Struct Dyn 2017; 36:407-422. [PMID: 28054501 DOI: 10.1080/07391102.2017.1279078] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive accumulation of amyloid-beta (Aβ) peptides in brain. In the present study, two familial Aβ42 mutations, namely A2V (harmful) and A2T (protective) have been analyzed and compared with the wild-type (WT) by performing all-atom molecular dynamics (MD) simulations in the absence and presence of curcumin, a well-known inhibitor of Aβ plaque formation. Mutant A2V was found to exhibit highest stability followed by WT and mutant A2T in the absence of curcumin. This stability trend was found to be reversed in the presence of curcumin, suggesting a significant change in the conformational landscape of Aβ42 folding. Due to significant differences in the folding and interaction patterns of the mutants A2V and A2T, curcumin exhibited higher binding affinity for mutant A2T as compared to that of A2V. To the best of our knowledge, this is the first report on the effect of curcumin binding on structural landscapes of the two contrasting point mutants providing an understanding of the basis of Aβ plaque formation and its prevention by curcumin.
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Affiliation(s)
- Manika Awasthi
- a Bioinformatics Infrastructure Facility, Center of Excellence in Bioinformatics, Department of Biochemistry , University of Lucknow , Lucknow 226007 , India
| | - Swati Singh
- a Bioinformatics Infrastructure Facility, Center of Excellence in Bioinformatics, Department of Biochemistry , University of Lucknow , Lucknow 226007 , India
| | - Veda P Pandey
- a Bioinformatics Infrastructure Facility, Center of Excellence in Bioinformatics, Department of Biochemistry , University of Lucknow , Lucknow 226007 , India
| | - Upendra N Dwivedi
- a Bioinformatics Infrastructure Facility, Center of Excellence in Bioinformatics, Department of Biochemistry , University of Lucknow , Lucknow 226007 , India
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MacLea KS. What Makes a Prion: Infectious Proteins From Animals to Yeast. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 329:227-276. [PMID: 28109329 DOI: 10.1016/bs.ircmb.2016.08.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
While philosophers in ancient times had many ideas for the cause of contagion, the modern study of infective agents began with Fracastoro's 1546 proposal that invisible "spores" spread infectious disease. However, firm categorization of the pathogens of the natural world would need to await a mature germ theory that would not arise for 300 years. In the 19th century, the earliest pathogens described were bacteria and other cellular microbes. By the close of that century, the work of Ivanovsky and Beijerinck introduced the concept of a virus, an infective particle smaller than any known cell. Extending into the early-mid-20th century there was an explosive growth in pathogenic microbiology, with a cellular or viral cause identified for nearly every transmissible disease. A few occult pathogens remained to be discovered, including the infectious proteins (prions) proposed by Prusiner in 1982. This review discusses the prions identified in mammals, yeasts, and other organisms, focusing on the amyloid-based prions. I discuss the essential biochemical properties of these agents and the application of this knowledge to diseases of protein misfolding and aggregation, as well as the utility of yeast as a model organism to study prion and amyloid proteins that affect human and animal health. Further, I summarize the ideas emerging out of these studies that the prion concept may go beyond proteinaceous infectious particles and that prions may be a subset of proteins having general nucleating or seeding functions involved in noninfectious as well as infectious pathogenic protein aggregation.
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Affiliation(s)
- K S MacLea
- University of New Hampshire, Manchester, NH, United States.
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16
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Lahiri P, Schmidt V, Smole C, Kufferath I, Denk H, Strnad P, Rülicke T, Fröhlich LF, Zatloukal K. p62/Sequestosome-1 Is Indispensable for Maturation and Stabilization of Mallory-Denk Bodies. PLoS One 2016; 11:e0161083. [PMID: 27526095 PMCID: PMC4985067 DOI: 10.1371/journal.pone.0161083] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 07/31/2016] [Indexed: 11/19/2022] Open
Abstract
Mallory-Denk bodies (MDBs) are hepatocytic protein aggregates found in steatohepatitis and several other chronic liver diseases as well as hepatocellular carcinoma. MDBs are mainly composed of phosphorylated keratins and stress protein p62/Sequestosome-1 (p62), which is a common component of cytoplasmic aggregates in a variety of protein aggregation diseases. In contrast to the well-established role of keratins, the role of p62 in MDB pathogenesis is still elusive. We have generated total and hepatocyte-specific p62 knockout mice, fed them with 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) to induce MDBs and allowed the mice to recover from DDC intoxication on a standard diet to investigate the role of p62 in MDB formation and elimination. In the absence of p62, smaller, granular and less distinct MDBs appeared, which failed to mature to larger and compact inclusions. Moreover, p62 deficiency impaired the binding of other proteins such as NBR1 and Hsp25 to MDBs and altered the cellular defense mechanism by downregulation of Nrf2 target genes. Upon recovery from DDC intoxication on a standard diet, there was an enhanced reduction of p62-deficient MDBs, which was accompanied by a pronounced decrease in ubiquitinated proteins. Our data provide strong evidence that keratin aggregation is the initial step in MDB formation in steatohepatitis-related mouse models. Interaction of p62 with keratin aggregates then leads to maturation i.e., enlargement and stabilization of the MDBs as well as recruitment of other MDB-associated proteins.
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Affiliation(s)
- Pooja Lahiri
- Institute of Pathology, Medical University of Graz, Graz, Austria
| | - Volker Schmidt
- Institute of Laboratory Animal Science, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Claudia Smole
- Institute of Pathology, Medical University of Graz, Graz, Austria
| | - Iris Kufferath
- Institute of Pathology, Medical University of Graz, Graz, Austria
| | - Helmut Denk
- Institute of Pathology, Medical University of Graz, Graz, Austria
| | - Pavel Strnad
- IZKF and Department of Internal Medicine III, Aachen, Germany
| | - Thomas Rülicke
- Institute of Laboratory Animal Science, University of Veterinary Medicine Vienna, Vienna, Austria
| | | | - Kurt Zatloukal
- Institute of Pathology, Medical University of Graz, Graz, Austria
- * E-mail:
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Naeem A, Bhat SA, Iram A, Khan RH. Aggregation of intrinsically disordered fibrinogen as the influence of backbone conformation. Arch Biochem Biophys 2016; 603:38-47. [DOI: 10.1016/j.abb.2016.04.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 04/13/2016] [Accepted: 04/30/2016] [Indexed: 10/21/2022]
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18
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Chakraborty B, Bhakta S, Sengupta J. Mechanistic Insight into the Reactivation of BCAII Enzyme from Denatured and Molten Globule States by Eukaryotic Ribosomes and Domain V rRNAs. PLoS One 2016; 11:e0153928. [PMID: 27099964 PMCID: PMC4839638 DOI: 10.1371/journal.pone.0153928] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2015] [Accepted: 04/06/2016] [Indexed: 12/29/2022] Open
Abstract
In all life forms, decoding of messenger-RNA into polypeptide chain is accomplished by the ribosome. Several protein chaperones are known to bind at the exit of ribosomal tunnel to ensure proper folding of the nascent chain by inhibiting their premature folding in the densely crowded environment of the cell. However, accumulating evidence suggests that ribosome may play a chaperone role in protein folding events in vitro. Ribosome-mediated folding of denatured proteins by prokaryotic ribosomes has been studied extensively. The RNA-assisted chaperone activity of the prokaryotic ribosome has been attributed to the domain V, a span of 23S rRNA at the intersubunit side of the large subunit encompassing the Peptidyl Transferase Centre. Evidently, this functional property of ribosome is unrelated to the nascent chain protein folding at the exit of the ribosomal tunnel. Here, we seek to scrutinize whether this unique function is conserved in a primitive kinetoplastid group of eukaryotic species Leishmania donovani where the ribosome structure possesses distinct additional features and appears markedly different compared to other higher eukaryotic ribosomes. Bovine Carbonic Anhydrase II (BCAII) enzyme was considered as the model protein. Our results manifest that domain V of the large subunit rRNA of Leishmania ribosomes preserves chaperone activity suggesting that ribosome-mediated protein folding is, indeed, a conserved phenomenon. Further, we aimed to investigate the mechanism underpinning the ribosome-assisted protein reactivation process. Interestingly, the surface plasmon resonance binding analyses exhibit that rRNA guides productive folding by directly interacting with molten globule-like states of the protein. In contrast, native protein shows no notable affinity to the rRNA. Thus, our study not only confirms conserved, RNA-mediated chaperoning role of ribosome but also provides crucial insight into the mechanism of the process.
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Affiliation(s)
- Biprashekhar Chakraborty
- Structural Biology & Bio-Informatics Division, Indian Institute of Chemical Biology (Council of Scientific & Industrial Research), 4, Raja S.C. Mullick Road, Kolkata, 700 032, India
| | - Sayan Bhakta
- Structural Biology & Bio-Informatics Division, Indian Institute of Chemical Biology (Council of Scientific & Industrial Research), 4, Raja S.C. Mullick Road, Kolkata, 700 032, India
| | - Jayati Sengupta
- Structural Biology & Bio-Informatics Division, Indian Institute of Chemical Biology (Council of Scientific & Industrial Research), 4, Raja S.C. Mullick Road, Kolkata, 700 032, India
- * E-mail:
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19
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Eftekharzadeh B, Hyman BT, Wegmann S. Structural studies on the mechanism of protein aggregation in age related neurodegenerative diseases. Mech Ageing Dev 2016; 156:1-13. [PMID: 27005270 DOI: 10.1016/j.mad.2016.03.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 02/12/2016] [Accepted: 03/03/2016] [Indexed: 01/09/2023]
Abstract
The progression of many neurodegenerative diseases is assumed to be caused by misfolding of specific characteristic diseases related proteins, resulting in aggregation and fibril formation of these proteins. Protein misfolding associated age related diseases, although different in disease manifestations, share striking similarities. In all cases, one disease protein aggregates and loses its function or additionally shows a toxic gain of function. However, the clear link between these individual amyloid-like protein aggregates and cellular toxicity is often still uncertain. The similar features of protein misfolding and aggregation in this group of proteins, all involved in age related neurodegenerative diseases, results in high interest in characterization of their structural properties. We review here recent findings on structural properties of some age related disease proteins, in the context of their biological importance in disease.
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Affiliation(s)
- Bahareh Eftekharzadeh
- Department of Neurology, Massachusetts General Hospital and Mass General Institute for Neurodegenerative Disease, Charlestown, MA 02129, USA.
| | - Bradley T Hyman
- Department of Neurology, Massachusetts General Hospital and Mass General Institute for Neurodegenerative Disease, Charlestown, MA 02129, USA
| | - Susanne Wegmann
- Department of Neurology, Massachusetts General Hospital and Mass General Institute for Neurodegenerative Disease, Charlestown, MA 02129, USA
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20
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Eukaryotic aggresomes: from a model of conformational diseases to an emerging type of immobilized biocatalyzers. Appl Microbiol Biotechnol 2015; 100:559-69. [DOI: 10.1007/s00253-015-7107-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 10/14/2015] [Accepted: 10/15/2015] [Indexed: 12/28/2022]
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21
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Atomistic characterization of binding modes and affinity of peptide inhibitors to amyloid-β protein. Front Chem Sci Eng 2014. [DOI: 10.1007/s11705-014-1454-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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22
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McMorran LM, Brockwell DJ, Radford SE. Mechanistic studies of the biogenesis and folding of outer membrane proteins in vitro and in vivo: what have we learned to date? Arch Biochem Biophys 2014; 564:265-80. [PMID: 24613287 PMCID: PMC4262575 DOI: 10.1016/j.abb.2014.02.011] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 02/16/2014] [Accepted: 02/20/2014] [Indexed: 11/17/2022]
Abstract
Research into the mechanisms by which proteins fold into their native structures has been on-going since the work of Anfinsen in the 1960s. Since that time, the folding mechanisms of small, water-soluble proteins have been well characterised. By contrast, progress in understanding the biogenesis and folding mechanisms of integral membrane proteins has lagged significantly because of the need to create a membrane mimetic environment for folding studies in vitro and the difficulties in finding suitable conditions in which reversible folding can be achieved. Improved knowledge of the factors that promote membrane protein folding and disfavour aggregation now allows studies of folding into lipid bilayers in vitro to be performed. Consequently, mechanistic details and structural information about membrane protein folding are now emerging at an ever increasing pace. Using the panoply of methods developed for studies of the folding of water-soluble proteins. This review summarises current knowledge of the mechanisms of outer membrane protein biogenesis and folding into lipid bilayers in vivo and in vitro and discusses the experimental techniques utilised to gain this information. The emerging knowledge is beginning to allow comparisons to be made between the folding of membrane proteins with current understanding of the mechanisms of folding of water-soluble proteins.
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Affiliation(s)
- Lindsay M McMorran
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - David J Brockwell
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK.
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23
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Liebert A, Bicknell B, Adams R. Prion Protein Signaling in the Nervous System—A Review and Perspective. ACTA ACUST UNITED AC 2014. [DOI: 10.4137/sti.s12319] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Prion protein (PrPC) was originally known as the causative agent of transmissible spongiform encephalopathy (TSE) but with recent research, its true function in cells is becoming clearer. It is known to act as a scaffolding protein, binding multiple ligands at the cell membrane and to be involved in signal transduction, passing information from the extracellular matrix (ECM) to the cytoplasm. Its role in the coordination of transmitters at the synapse, glyapse, and gap junction and in short- and long-range neurotrophic signaling gives PrPC a major part in neural transmission and nervous system signaling. It acts to regulate cellular function in multiple targets through its role as a controller of redox status and calcium ion flux. Given the importance of PrPC in cell physiology, this review considers its potential role in disease apart from TSE. The putative functions of PrPC point to involvement in neurodegenerative disease, neuropathic pain, chronic headache, and inflammatory disease including neuroinflammatory disease of the nervous system. Potential targets for the treatment of disease influenced by PrPC are discussed.
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Affiliation(s)
- Ann Liebert
- Faculty of Health Science, University of Sydney, Australia
| | - Brian Bicknell
- Faculty of Health Science, Australian Catholic University, Australia
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24
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Bhat SA, Bano B. Conformational behaviour and aggregation of chickpea cystatin in trifluoroethanol: effects of epicatechin and tannic acid. Arch Biochem Biophys 2014; 562:51-61. [PMID: 25173679 DOI: 10.1016/j.abb.2014.08.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Revised: 08/12/2014] [Accepted: 08/20/2014] [Indexed: 11/29/2022]
Abstract
Conformational alterations and aggregates of chickpea cystatin (CPC) were investigated upon sequential addition of trifluoroethanol (TFE) over a range of 0-70% v/v. CPC on 30% and 40% v/v TFE addition exhibited non-native β-sheet, altered intrinsic fluorescence, increased thioflavin T fluorescence, prominent red shifted shoulder peak in Congo red absorbance, and enhanced turbidity as well as Rayleigh scattering, suggesting the aggregate formation. TEM results confirmed the formation of fibrillar aggregates at 30% and 40% v/v TFE. On increasing concentration of TFE to 70% v/v, CPC showed retention of native-like secondary structure, increased intrinsic and ANS fluorescence. Thus our results show that favourable condition for fibrillation of CPC is in the range of 30-40% TFE. Moreover, anti-aggregational effects of polyphenols, epicatechin (EC) and tannic acid (TA) were analysed using ThT binding assay and other biophysical assays. EC and TA produced a concentration dependent decline in ThT fluorescence suggesting inhibition of the fibril formation. Furthermore, TA in comparison to EC, served as a more effective inhibitor against amyloid fibril formation of CPC. This work supports the universality of the amyloid-like aggregation not restricted to some special categories of protein and the fact that this aggregation can be prevented.
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Affiliation(s)
- Sheraz Ahmad Bhat
- Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh 202002, India
| | - Bilqees Bano
- Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh 202002, India.
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25
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Murakami A. Dose-dependent functionality and toxicity of green tea polyphenols in experimental rodents. Arch Biochem Biophys 2014; 557:3-10. [PMID: 24814373 DOI: 10.1016/j.abb.2014.04.018] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Revised: 03/31/2014] [Accepted: 04/29/2014] [Indexed: 01/09/2023]
Abstract
A large number of physiologically functional foods are comprised of plant polyphenols. Their antioxidative activities have been intensively studied for a long period and proposed to be one of the major mechanisms of action accounting for their health promotional and disease preventive effects. Green tea polyphenols (GTPs) are considered to possess marked anti-oxidative properties and versatile beneficial functions, including anti-inflammation and cancer prevention. On the other hand, some investigators, including us, have uncovered their toxicity at high doses presumably due to pro-oxidative properties. For instance, both experimental animal studies and epidemiological surveys have demonstrated that GTPs may cause hepatotoxicity. We also recently showed that diets containing high doses (0.5-1%) of a GTP deteriorated dextran sodium sulfate (DSS)-induced intestinal inflammation and carcinogenesis. In addition, colitis mode mice fed a 1% GTP exhibited symptoms of nephrotoxicity, as indicated by marked elevation of serum creatinine level. This diet also increased thiobarbituric acid-reactive substances, a reliable marker of oxidative damage, in both kidneys and livers even in normal mice, while the expression levels of antioxidant enzymes and heat shock proteins (HSPs) were diminished in colitis and normal mice. Intriguingly, GTPs at 0.01% and 0.1% showed hepato-protective activities, i.e., they significantly suppressed DSS-increased serum aspartate aminotransferase and alanine aminotransferase levels. Moreover, those diets remarkably restored DSS-down-regulated expressions of heme oxygenase-1 and HSP70 in livers and kidneys. Taken together, while low and medium doses of GTPs are beneficial in colitis model mice, unwanted side-effects occasionally emerge with high doses. This dose-dependent functionality and toxicity of GTPs are in accordance with the concept of hormesis, in which mild, but not severe, stress activates defense systems for adaptation and survival.
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Affiliation(s)
- Akira Murakami
- Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto, 606-8502, Japan.
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26
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Amani S, Naeem A. Deciphering aggregates, prefibrillar oligomers and protofibrils of cytochrome c. Amino Acids 2014; 46:1839-51. [DOI: 10.1007/s00726-014-1698-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 02/14/2014] [Indexed: 11/28/2022]
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Protein conformational transitions at the liquid-gas interface as studied by dilational surface rheology. Adv Colloid Interface Sci 2014; 206:222-38. [PMID: 24238394 DOI: 10.1016/j.cis.2013.10.024] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2013] [Revised: 10/21/2013] [Accepted: 10/21/2013] [Indexed: 11/21/2022]
Abstract
Experimental results on the dynamic dilational surface elasticity of protein solutions are analyzed and compared. Short reviews of the protein behavior at the liquid-gas interface and the dilational surface rheology precede the main sections of this work. The kinetic dependencies of the surface elasticity differ strongly for the solutions of globular and non-globular proteins. In the latter case these dependencies are similar to those for solutions of non-ionic amphiphilic polymers and have local maxima corresponding to the formation of the distal region of the surface layer (type I). In the former case the dynamic surface elasticity is much higher (>60 mN/m) and the kinetic dependencies are monotonical and similar to the data for aqueous dispersions of solid nanoparticles (type II). The addition of strong denaturants to solutions of bovine serum albumin and β-lactoglobulin results in an abrupt transition from the type II to type I dependencies if the denaturant concentration exceeds a certain critical value. These results give a strong argument in favor of the preservation of the protein globular structure in the course of adsorption without any denaturants. The addition of cationic surfactants also can lead to the non-monotonical kinetic dependencies of the dynamic surface elasticity indicating destruction of the protein tertiary and secondary structures. The addition of anionic surfactants gives similar results only for the protein solutions of high ionic strength. The influence of cationic surfactants on the local maxima of the kinetic dependencies of the dynamic surface elasticity for solutions of a non-globular protein (β-casein) differs from the influence of anionic surfactants due to the heterogeneity of the charge distribution along the protein chain. In this case one can use small admixtures of ionic surfactants as probes of the adsorption mechanism. The effect of polyelectrolytes on the kinetic dependencies of the dynamic surface elasticity of protein solutions is weaker than the effect of conventional surfactants but exceeds the error limits.
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Induction of amyloidogenicity in wild type HEWL by a dialdehyde: Analysis involving multi dimensional approach. Int J Biol Macromol 2014; 64:36-44. [DOI: 10.1016/j.ijbiomac.2013.11.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Revised: 11/17/2013] [Accepted: 11/18/2013] [Indexed: 11/23/2022]
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In vitro hyperglycemic condition facilitated the aggregation of lysozyme via the passage through a molten globule state. Cell Biochem Biophys 2013. [PMID: 23184703 DOI: 10.1007/s12013-012-9479-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Hyperglycemic condition i.e. an increase in blood glucose concentration has been linked to bring about structural alterations in the native state of proteins. Glucose concentrations of 50 and 100 mM in vitro, which correspond to hyperglycemic condition, were tested to investigate their effect on lysozyme native structure. Incubating enzyme with 50 and 100 mM glucose for a period of 7 days, an intermediate state on day 4 and 3 was observed, respectively. The presence of intermediate state was characterized by a 22 % increase in the intrinsic fluorescence intensity with a red shift of 20 nm compared to the native state, a 5 % increase in ANS-fluorescence intensity relative to the native due to the surfacing of hydrophobic clusters and a sharp decrease in near-UV CD signal at around 284 and 291 nm. The state retains substantial native-like secondary structure. This partially unfolded intermediate state can be referred as 'molten globule', which finally tends to aggregate on day 6 and 4 with 50 and 100 mM glucose concentration, respectively, as a result of cross-linking between lysozyme molecules. The aggregates were confirmed by the presence of β-sheet structure as depicted by far-UV CD, an increase in ThT fluorescence as well as the fibrillar morphology shown by SEM. Moreover, advanced glycation end products were also accompanied as the emission peak was observed at 460 and 470 nm corresponding to the formation of pentosidine and malonaldehyde, respectively.
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30
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31
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Iram A, Alam T, Khan JM, Khan TA, Khan RH, Naeem A. Molten globule of hemoglobin proceeds into aggregates and advanced glycated end products. PLoS One 2013; 8:e72075. [PMID: 23991043 PMCID: PMC3753358 DOI: 10.1371/journal.pone.0072075] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Accepted: 07/05/2013] [Indexed: 02/06/2023] Open
Abstract
Conformational alterations of bovine hemoglobin (Hb) upon sequential addition of glyoxal over a range of 0–90% v/v were investigated. At 20% v/v glyoxal, molten globule (MG) state of Hb was observed by altered tryptophan fluorescence, high ANS binding, existence of intact heme, native-like secondary structure as depicted by far-UV circular dichroism (CD) and ATR-FTIR spectra as well as loss in tertiary structure as confirmed by near-UV CD spectra. In addition, size exclusion chromatography analysis depicted that MG state at 20% v/v glyoxal corresponded to expanded pre-dissociated dimers. Aggregates of Hb were detected at 70% v/v glyoxal. These aggregates of Hb had altered tryptophan environment, low ANS binding, exposed heme, increased β-sheet secondary structure, loss in tertiary structure, enhanced thioflavin T (ThT) fluorescence and red shifted Congo Red (CR) absorbance. On incubating Hb with 30% v/v glyoxal for 0–20 days, advanced glycation end products (AGEs) were detected on day 20. These AGEs were characterised by enhanced tryptophan fluorescence at 450 nm, exposure of heme, increase in intermolecular β-sheets, enhanced ThT fluorescence and red shift in CR absorbance. Comet assay revealed aggregates and AGEs to be genotoxic in nature. Scanning electron microscopy confirmed the amorphous structure of aggregates and branched fibrils of AGEs. The transformation of α-helix to β-sheet usually alters the normal protein to amyloidogenic resulting in a variety of protein conformational disorders such as diabetes, prion and Huntington's.
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Affiliation(s)
- Afshin Iram
- Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh, India
| | - Tauqeer Alam
- Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh, India
| | - Javed M. Khan
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, India
| | - Taqi A. Khan
- Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh, India
| | - Rizwan H. Khan
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, India
| | - Aabgeena Naeem
- Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh, India
- * E-mail:
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Stefl S, Nishi H, Petukh M, Panchenko AR, Alexov E. Molecular mechanisms of disease-causing missense mutations. J Mol Biol 2013; 425:3919-36. [PMID: 23871686 DOI: 10.1016/j.jmb.2013.07.014] [Citation(s) in RCA: 187] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Revised: 07/04/2013] [Accepted: 07/10/2013] [Indexed: 12/23/2022]
Abstract
Genetic variations resulting in a change of amino acid sequence can have a dramatic effect on stability, hydrogen bond network, conformational dynamics, activity and many other physiologically important properties of proteins. The substitutions of only one residue in a protein sequence, so-called missense mutations, can be related to many pathological conditions and may influence susceptibility to disease and drug treatment. The plausible effects of missense mutations range from affecting the macromolecular stability to perturbing macromolecular interactions and cellular localization. Here we review the individual cases and genome-wide studies that illustrate the association between missense mutations and diseases. In addition, we emphasize that the molecular mechanisms of effects of mutations should be revealed in order to understand the disease origin. Finally, we report the current state-of-the-art methodologies that predict the effects of mutations on protein stability, the hydrogen bond network, pH dependence, conformational dynamics and protein function.
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Affiliation(s)
- Shannon Stefl
- Computational Biophysics and Bioinformatics, Department of Physics, Clemson University, Clemson, SC 29634, USA
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33
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Mulligan VK, Chakrabartty A. Protein misfolding in the late-onset neurodegenerative diseases: Common themes and the unique case of amyotrophic lateral sclerosis. Proteins 2013; 81:1285-303. [DOI: 10.1002/prot.24285] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Revised: 02/27/2013] [Accepted: 02/28/2013] [Indexed: 12/12/2022]
Affiliation(s)
| | - Avijit Chakrabartty
- Department of Biochemistry; Toronto Ontario M5G 1L7 Canada
- Department of Medical Biophysics; University of Toronto; Toronto Ontario M5G 1L7 Canada
- Campbell Family Institute for Cancer Research, Ontario Cancer Institute/University Health Network; Toronto Ontario M5G 1L7 Canada
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Sefidbakht Y, Hosseinkhani S, Mortazavi M, Tavakkolnia I, Khellat MR, Shakiba-Herfeh M, Saviz M, Faraji-Dana R, Saboury AA, Sheibani N, Moosavi-Movahedi AA. Effects of 940 MHz EMF on luciferase solution: Structure, function, and dielectric studies. Bioelectromagnetics 2013; 34:489-98. [DOI: 10.1002/bem.21792] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Accepted: 03/14/2013] [Indexed: 11/06/2022]
Affiliation(s)
- Yahya Sefidbakht
- Institute of Biochemistry and Biophysics (IBB); University of Tehran; Tehran; Iran
| | - Saman Hosseinkhani
- Faculty of Biological Sciences, Department of Biochemistry; Tarbiat Modares University; Tehran; Iran
| | - Mojtaba Mortazavi
- Faculty of Biological Sciences, Department of Biochemistry; Tarbiat Modares University; Tehran; Iran
| | - Iman Tavakkolnia
- School of Electrical and Computer Engineering; University of Tehran; Tehran; Iran
| | - Mohammad R. Khellat
- Institute of Biochemistry and Biophysics (IBB); University of Tehran; Tehran; Iran
| | - Mahdi Shakiba-Herfeh
- School of Electrical and Computer Engineering; University of Tehran; Tehran; Iran
| | - Mehrdad Saviz
- School of Electrical and Computer Engineering; University of Tehran; Tehran; Iran
| | - Reza Faraji-Dana
- School of Electrical and Computer Engineering; University of Tehran; Tehran; Iran
| | | | - Nader Sheibani
- Department of Ophthalmology and Visual Sciences and Pharmacology; University of Wisconsin School of Medicine and Public Health; Madison, Wisconsin
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35
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Iram A, Naeem A. Detection and analysis of protofibrils and fibrils of hemoglobin: implications for the pathogenesis and cure of heme loss related maladies. Arch Biochem Biophys 2013; 533:69-78. [PMID: 23500139 DOI: 10.1016/j.abb.2013.02.019] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 02/25/2013] [Accepted: 02/27/2013] [Indexed: 01/17/2023]
Abstract
TFE induces structural alterations of proteins similar to the lipid environment of biological membranes, implicating these studies worthy of analyzing protein conformation in membranes such as red blood cells (RBCs). Heme loss occurs on rupturing of RBCs as found in diseases namely haemophilia, haemolytic anaemia, diabetes mellitus. TFE can be implied in discovering therapeutic targets, as it mimics the biological membrane environment. A global transition of hemoglobin (Hb) in presence of TFE was studied by using multi-methodological approach. The presence of partially folded state of Hb at 15% v/v TFE was confirmed by altered tryptophan environment, and retention of native-like secondary and tertiary structure. Molten globule state was observed at 20% v/v TFE as detected by increase tryptophan and high ANS fluorescence, slight alterations in Soret band relative to native. TFE on increasing concentration induced protofibrils at 25% v/v and fibrils at 45% v/v as depicted by altered tryptophan environment, heme loss, increase in non-native β-sheet secondary and tertiary structure, large hydrodynamic radii of heme-protein, high ANS, thioflavin T fluorescence and shift in Congo Red absorbance. Comet assay showed that protofibrils are cytotoxic to lymphocytes. SEM and XRD confirmed these aggregates to be fibrillar in nature.
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Affiliation(s)
- Afshin Iram
- Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh 202002, India
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Burke KA, Yates EA, Legleiter J. Biophysical insights into how surfaces, including lipid membranes, modulate protein aggregation related to neurodegeneration. Front Neurol 2013; 4:17. [PMID: 23459674 PMCID: PMC3585431 DOI: 10.3389/fneur.2013.00017] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 02/09/2013] [Indexed: 11/13/2022] Open
Abstract
There are a vast number of neurodegenerative diseases, including Alzheimer’s disease (AD), Parkinson’s disease (PD), and Huntington’s disease (HD), associated with the rearrangement of specific proteins to non-native conformations that promotes aggregation and deposition within tissues and/or cellular compartments. These diseases are commonly classified as protein-misfolding or amyloid diseases. The interaction of these proteins with liquid/surface interfaces is a fundamental phenomenon with potential implications for protein-misfolding diseases. Kinetic and thermodynamic studies indicate that significant conformational changes can be induced in proteins encountering surfaces, which can play a critical role in nucleating aggregate formation or stabilizing specific aggregation states. Surfaces of particular interest in neurodegenerative diseases are cellular and subcellular membranes that are predominately comprised of lipid components. The two-dimensional liquid environments provided by lipid bilayers can profoundly alter protein structure and dynamics by both specific and non-specific interactions. Importantly for misfolding diseases, these bilayer properties can not only modulate protein conformation, but also exert influence on aggregation state. A detailed understanding of the influence of (sub)cellular surfaces in driving protein aggregation and/or stabilizing specific aggregate forms could provide new insights into toxic mechanisms associated with these diseases. Here, we review the influence of surfaces in driving and stabilizing protein aggregation with a specific emphasis on lipid membranes.
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Affiliation(s)
- Kathleen A Burke
- C. Eugene Bennett Department of Chemistry, West Virginia University Morgantown, WV, USA
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Consequential secondary structure alterations and aggregation during prolonged casein glycation. J Fluoresc 2013; 23:367-74. [DOI: 10.1007/s10895-013-1162-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Accepted: 10/23/2012] [Indexed: 01/12/2023]
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Naeem A, Amani S. Deciphering structural intermediates and genotoxic fibrillar aggregates of albumins: a molecular mechanism underlying for degenerative diseases. PLoS One 2013; 8:e54061. [PMID: 23342075 PMCID: PMC3544675 DOI: 10.1371/journal.pone.0054061] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Accepted: 12/05/2012] [Indexed: 11/23/2022] Open
Abstract
The misfolding and aggregation of proteins is involved in some of the most prevalent neurodegenerative disorders. The importance of human serum albumin (HSA) stems from the fact that it is involved in bio-regulatory and transport phenomena. Here the effect of acetonitrile (ACN) on the conformational stability of HSA and by comparison, ovalbumin (OVA) has been evaluated in the presence and absence of NaCl. The results show the presence of significant amount of secondary structure in HSA at 70% ACN and in OVA at 50% ACN, as evident from far-UV Circular Dichroism (CD) and Attenuated Total Reflection Fourier transformed infra red spectroscopy (ATR-FTIR). Tryptophan and 8-Anilino-1-Naphthalene-Sulphonic acid (ANS) fluorescence indicate altered tryptophan environment and high ANS binding suggesting a compact “molten globule”-like conformation with enhanced exposure of hydrophobic surface area. However, in presence of NaCl no intermediate state was observed. Detection of aggregates in HSA and OVA was possible at 90% ACN. Aggregates possess extensive β-sheet structure as revealed by far-UV CD and ATR-FTIR. These aggregates exhibit increase Thioflavin T (Th T) fluorescence with a red shift of Congo red (CR) absorption spectrum. X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) analysis confirmed the presence of fibrillar aggregates. Single cell gel electrophoresis (SCGE) assay of these fibrillar aggregates showed the DNA damage resulting in cell necrosis confirming their genotoxic nature. Some proteins not related to any human disease form fibrils in vitro. In the present study ACN gives access to a model system to study the process of aggregation.
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Affiliation(s)
- Aabgeena Naeem
- Department of Biochemistry, Faculty of Life Science, Aligarh Muslim University, Aligarh, Uttar Pradesh, India.
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Iram A, Amani S, Furkan M, Naeem A. Equilibrium studies of cellulase aggregates in presence of ascorbic and boric acid. Int J Biol Macromol 2013; 52:286-95. [DOI: 10.1016/j.ijbiomac.2012.10.023] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Revised: 09/08/2012] [Accepted: 10/19/2012] [Indexed: 11/17/2022]
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Roche J, Dellarole M, Caro JA, Guca E, Norberto DR, Yang Y, Garcia AE, Roumestand C, García-Moreno B, Royer CA. Remodeling of the folding free energy landscape of staphylococcal nuclease by cavity-creating mutations. Biochemistry 2012; 51:9535-46. [PMID: 23116341 DOI: 10.1021/bi301071z] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The folding of staphylococcal nuclease (SNase) is known to proceed via a major intermediate in which the central OB subdomain is folded and the C-terminal helical subdomain is disordered. To identify the structural and energetic determinants of this folding free energy landscape, we have examined in detail, using high-pressure NMR, the consequences of cavity creating mutations in each of the two subdomains of an ultrastable SNase, Δ+PHS. The stabilizing mutations of Δ+PHS enhanced the population of the major folding intermediate. Cavity creation in two different regions of the Δ+PHS reference protein, despite equivalent effects on global stability, had very distinct consequences on the complexity of the folding free energy landscape. The L125A substitution in the C-terminal helix of Δ+PHS slightly suppressed the major intermediate and promoted an additional excited state involving disorder in the N-terminus, but otherwise decreased landscape heterogeneity with respect to the Δ+PHS background protein. The I92A substitution, located in the hydrophobic OB-fold core, had a much more profound effect, resulting in a significant increase in the number of intermediate states and implicating the entire protein structure. Denaturant (GuHCl) had very subtle and specific effects on the landscape, suppressing some states and favoring others, depending upon the mutational context. These results demonstrate that disrupting interactions in a region of the protein with highly cooperative, unfrustrated folding has very profound effects on the roughness of the folding landscape, whereas the effects are less pronounced for an energetically equivalent substitution in an already frustrated region.
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Affiliation(s)
- Julien Roche
- Centre de Biochimie Structurale, INSERM U554, CNRS UMR 5048, Universités de Montpellier, Montpellier, France
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Iram A, Naeem A. Conformational Transitions Provoked by Organic Solvents in Chicken Egg Ovalbumin: Mimicking the Local Environment. Protein J 2012; 32:7-14. [DOI: 10.1007/s10930-012-9453-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Grasso G, Spoto G. Plasmonics for the study of metal ion–protein interactions. Anal Bioanal Chem 2012; 405:1833-43. [DOI: 10.1007/s00216-012-6421-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Revised: 09/10/2012] [Accepted: 09/12/2012] [Indexed: 12/19/2022]
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Xu Z, Lazim R, Sun T, Mei Y, Zhang D. Solvent effect on the folding dynamics and structure of E6-associated protein characterized from ab initio protein folding simulations. J Chem Phys 2012; 136:135102. [PMID: 22482589 DOI: 10.1063/1.3698164] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Solvent effect on protein conformation and folding mechanism of E6-associated protein (E6ap) peptide are investigated using a recently developed charge update scheme termed as adaptive hydrogen bond-specific charge (AHBC). On the basis of the close agreement between the calculated helix contents from AHBC simulations and experimental results, we observed based on the presented simulations that the two ends of the peptide may simultaneously take part in the formation of the helical structure at the early stage of folding and finally merge to form a helix with lowest backbone RMSD of about 0.9 Å in 40% 2,2,2-trifluoroethanol solution. However, in pure water, the folding may start at the center of the peptide sequence instead of at the two opposite ends. The analysis of the free energy landscape indicates that the solvent may determine the folding clusters of E6ap, which subsequently leads to the different final folded structure. The current study demonstrates new insight to the role of solvent in the determination of protein structure and folding dynamics.
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Affiliation(s)
- Zhijun Xu
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
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Liu FF, Liu Z, Bai S, Dong XY, Sun Y. Exploring the inter-molecular interactions in amyloid-β protofibril with molecular dynamics simulations and molecular mechanics Poisson-Boltzmann surface area free energy calculations. J Chem Phys 2012; 136:145101. [PMID: 22502547 DOI: 10.1063/1.3702195] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Aggregation of amyloid-β (Aβ) peptides correlates with the pathology of Alzheimer's disease. However, the inter-molecular interactions between Aβ protofibril remain elusive. Herein, molecular mechanics Poisson-Boltzmann surface area analysis based on all-atom molecular dynamics simulations was performed to study the inter-molecular interactions in Aβ(17-42) protofibril. It is found that the nonpolar interactions are the important forces to stabilize the Aβ(17-42) protofibril, while electrostatic interactions play a minor role. Through free energy decomposition, 18 residues of the Aβ(17-42) are identified to provide interaction energy lower than -2.5 kcal/mol. The nonpolar interactions are mainly provided by the main chain of the peptide and the side chains of nine hydrophobic residues (Leu17, Phe19, Phe20, Leu32, Leu34, Met35, Val36, Val40, and Ile41). However, the electrostatic interactions are mainly supplied by the main chains of six hydrophobic residues (Phe19, Phe20, Val24, Met35, Val36, and Val40) and the side chains of the charged residues (Glu22, Asp23, and Lys28). In the electrostatic interactions, the overwhelming majority of hydrogen bonds involve the main chains of Aβ as well as the guanidinium group of the charged side chain of Lys28. The work has thus elucidated the molecular mechanism of the inter-molecular interactions between Aβ monomers in Aβ(17-42) protofibril, and the findings are considered critical for exploring effective agents for the inhibition of Aβ aggregation.
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Affiliation(s)
- Fu-Feng Liu
- Department of Biochemical Engineering and Key Laboratory of Systems Bioengineering of the Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
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Iram A, Naeem A. Trifluoroethanol and acetonitrile induced formation of the molten globule states and aggregates of cellulase. Int J Biol Macromol 2012; 50:932-8. [DOI: 10.1016/j.ijbiomac.2012.02.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Existence of different structural intermediates and aggregates on the folding pathway of ovalbumin. J Fluoresc 2011; 22:47-57. [PMID: 21837385 DOI: 10.1007/s10895-011-0929-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Accepted: 07/28/2011] [Indexed: 12/21/2022]
Abstract
Structural modifications of ovalbumin in presence of different concentration of guanidine hydrochloride (Gdn HCl) and glucose were investigated by using intrinsic fluorescence, Fourier transform infra-red spectroscopy, circular dichroism and 8-anilino-1-naphthalene-sulphonic acid, to confirm that partially folded intermediates of ovalbumin lead to aggregation. The two partially folded intermediates of ovalbumin were observed one at 1 M Gdn HCl and another in the presence of 20 mM glucose at 3 M Gdn HCl. Both intermediates exist as compact states with altered intrinsic fluorescence, prominent β-sheet secondary structure and enhanced ANS binding. Ovalbumin in the presence of glucose required more concentration of Gdn HCl (3 M) to exist as an intermediate state than control (1 M). Such alpha-helix/beta-sheet transition of proteins is a crucial step in amyloidogenic diseases and represents an internal rearrangement of local contacts in an already folded protein. Further, incubation for 24 h resulted in the formation of aggregates as detected by thioflavin T-assay. On further increasing the concentration of glucose to 50 mM and incubation time for various days resulted in the formation of molten globule state of ovalbumin at 6th day. Later on, at 10th day advanced glycated end products were observed.
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