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Fagerberg E, Månsson LK, Lenton S, Skepö M. The Effects of Chain Length on the Structural Properties of Intrinsically Disordered Proteins in Concentrated Solutions. J Phys Chem B 2020; 124:11843-11853. [PMID: 33337879 PMCID: PMC7872433 DOI: 10.1021/acs.jpcb.0c09635] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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Intrinsically disordered proteins (IDP) are proteins that sample
a heterogeneous ensemble of conformers in solution. An estimated 25–30%
of all eukaryotic proteins belong to this class. In vivo, IDPs function under conditions that are highly crowded by other
biological macromolecules. Previous research has highlighted that
the presence of crowding agents can influence the conformational ensemble
sampled by IDPs, resulting in either compaction or expansion. The
effects of self-crowding of the disordered protein Histatin 5 has,
in an earlier study, been found to have limited influence on the conformational
ensemble. In this study, it is examined whether the short chain length
of Histatin 5 can explain the limited effects of crowding observed,
by introducing (Histatin 5)2, a tandem repeat of Histatin
5. By utilizing small-angle X-ray scattering, it is shown that the
conformational ensemble is conserved at high protein concentrations,
in resemblance with Histatin 5, although with a lowered protein concentration
at which aggregation arises. Under dilute conditions, atomistic molecular
dynamics and coarse-grained Monte Carlo simulations, as well as an
established scaling law, predicted more extended conformations than
indicated by experimental data, hence implying that (Histatin 5)2 does not behave as a self-avoiding random walk.
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Affiliation(s)
- Eric Fagerberg
- Theoretical Chemistry, Lund University, P.O. Box 124, Lund SE-221 00, Sweden
| | - Linda K Månsson
- Theoretical Chemistry, Lund University, P.O. Box 124, Lund SE-221 00, Sweden
| | - Samuel Lenton
- Theoretical Chemistry, Lund University, P.O. Box 124, Lund SE-221 00, Sweden.,LINXS - Lund Institute of Advanced Neutron and X-ray Science, Scheelevägen 19, Lund SE-223 70, Sweden
| | - Marie Skepö
- Theoretical Chemistry, Lund University, P.O. Box 124, Lund SE-221 00, Sweden.,LINXS - Lund Institute of Advanced Neutron and X-ray Science, Scheelevägen 19, Lund SE-223 70, Sweden
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2
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Molecular insights into the inhibitory mechanism of bi-functional bis-tryptoline triazole against β-secretase (BACE1) enzyme. Amino Acids 2019; 51:1593-1607. [PMID: 31654211 DOI: 10.1007/s00726-019-02797-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Accepted: 10/04/2019] [Indexed: 02/07/2023]
Abstract
The β-site amyloid precursor protein-cleaving enzyme 1 (β-secretase, BACE1) is involved in the formation of amyloid-β (Aβ) peptide that aggregates into soluble oligomers, amyloid fibrils, and plaques responsible for the neurodegeneration in Alzheimer disease (AD). BACE1 is one of the prime therapeutic targets for the design of inhibitors against AD as BACE1 participate in the rate-limiting step in Aβ production. Jiaranaikulwanitch et al. reported bis-tryptoline triazole (BTT) compound as a potent inhibitor against BACE1, Aβ aggregation as well as possessing metal chelation and antioxidant activity. However, the molecular mechanism of BACE1 inhibition by BTT remains unclear. Thus, molecular docking and molecular dynamics (MD) simulations were performed to elucidate the inhibitory mechanism of BTT against BACE1. MD simulations highlight that BTT interact with catalytic aspartic dyad residues (Asp32 and Asp228) and active pocket residues of BACE1. The hydrogen-bond interactions, hydrophobic contacts, and π-π stacking interactions of BTT with flap residues (Val67-Asp77) of BACE1 confine the movement of the flap and help to achieve closed (non-active) conformation. The PCA analysis highlights lower conformational fluctuations for BACE1-BTT complex, which suggests enhanced conformational stability in comparison to apo-BACE1. The results of the present study provide key insights into the underlying inhibitory mechanism of BTT against BACE1 and will be helpful for the rational design of novel inhibitors with enhanced potency against BACE1.
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Martin EB, Williams A, Richey T, Wooliver C, Stuckey A, Foster JS, Kennel SJ, Wall JS. Evaluation of the effect of D-amino acid incorporation into amyloid-reactive peptides. J Transl Med 2017; 15:247. [PMID: 29228957 PMCID: PMC5725832 DOI: 10.1186/s12967-017-1351-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 11/25/2017] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Systemic amyloidoses comprise diseases characterized by the deposition of proteinaceous material known as amyloid. Currently, without performing multiple biopsies, there is no way to ascertain the extent of amyloid deposition in patients-a critical piece of information that informs prognosis and therapeutic strategies. We have developed pan-amyloid-targeting peptides for imaging amyloid and recently have adapted these for use as pre-targeting agents in conjunction with immunotherapy. Incorporation of D-amino acids in these peptides may enhance serum half-life, which is an important characteristic of effective peptide therapeutics. Herein, we assess the effects of partial incorporation of D-amino acids into the amyloidophilic peptide p5 on in vivo amyloid reactivity. METHODS Peptides, referred to as AQAp5 (d) , aqap5, and AQAp5, were radiolabeled with iodine-125 and the tissue biodistribution (% injected dose/gram) measured in healthy mice at multiple time points post-injection. Microscopic distribution of the peptides was further visualized using microautoradiography (ARG). Peptides aqap5 and AQAp5 were injected into healthy and amyloid-laden mice and evaluated by using SPECT/CT imaging at 1, 4 and 24 h post injection. RESULTS Biodistribution data and ARG revealed persistent retention of [125I]AQAp5 (d) in the liver and kidneys of healthy mice for at least 24 h. In contrast, peptides [125I]aqap5 and [125I]AQAp5 did not bind these organs and was significantly lower than [125I]AQAp5 (d) at 24 h post injection (p < 0.0001). SPECT/CT imaging of amyloid-laden mice revealed accumulation of both [125I]aqap5 and [125I]AQAp5 in amyloid-affected organs; whereas, in healthy mice, [125I]aqap5 was observed in the kidneys and liver at early time points, and free radioiodide liberated during catabolism of [125I]AQAp5 was seen in the stomach and thyroid. Autoradiography confirmed that both [125I]aqap5 and [125I]AQAp5 peptides specifically bound amyloid with no off-target binding to healthy organs. CONCLUSION Incorporation of D-amino acids in amyloid-binding regions of amyloidophilic peptides resulted in off-target binding; however, N-terminus placement retained amyloid-specificity and evasion of deiodinases. Peptide aqap5, or similar reagents, may prove useful in novel immunotherapy strategies as well as for imaging renal, gastric and pancreatic amyloidosis.
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Affiliation(s)
- Emily B Martin
- Department of Medicine, University of Tennessee Medical Center, 1924 Alcoa Hwy, Knoxville, TN, 37920, USA.
| | - Angela Williams
- Department of Medicine, University of Tennessee Medical Center, 1924 Alcoa Hwy, Knoxville, TN, 37920, USA
| | - Tina Richey
- Department of Medicine, University of Tennessee Medical Center, 1924 Alcoa Hwy, Knoxville, TN, 37920, USA
| | - Craig Wooliver
- Department of Medicine, University of Tennessee Medical Center, 1924 Alcoa Hwy, Knoxville, TN, 37920, USA
| | - Alan Stuckey
- Department of Radiology, University of Tennessee Medical Center, 1924 Alcoa Hwy, Knoxville, TN, 37920, USA
| | - James S Foster
- Department of Medicine, University of Tennessee Medical Center, 1924 Alcoa Hwy, Knoxville, TN, 37920, USA
| | - Stephen J Kennel
- Department of Medicine, University of Tennessee Medical Center, 1924 Alcoa Hwy, Knoxville, TN, 37920, USA.,Department of Radiology, University of Tennessee Medical Center, 1924 Alcoa Hwy, Knoxville, TN, 37920, USA
| | - Jonathan S Wall
- Department of Medicine, University of Tennessee Medical Center, 1924 Alcoa Hwy, Knoxville, TN, 37920, USA.,Department of Radiology, University of Tennessee Medical Center, 1924 Alcoa Hwy, Knoxville, TN, 37920, USA
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Saini RK, Shuaib S, Goyal B. Molecular insights into Aβ42protofibril destabilization with a fluorinated compound D744: A molecular dynamics simulation study. J Mol Recognit 2017; 30. [DOI: 10.1002/jmr.2656] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 07/25/2017] [Accepted: 07/26/2017] [Indexed: 12/13/2022]
Affiliation(s)
- Rajneet Kaur Saini
- Department of Chemistry, School of Basic and Applied Sciences; Sri Guru Granth Sahib World University; Fatehgarh Sahib Punjab India
| | - Suniba Shuaib
- Department of Chemistry, School of Basic and Applied Sciences; Sri Guru Granth Sahib World University; Fatehgarh Sahib Punjab India
| | - Bhupesh Goyal
- Department of Chemistry, School of Basic and Applied Sciences; Sri Guru Granth Sahib World University; Fatehgarh Sahib Punjab India
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Goyal B, Srivastava KR, Durani S. N-terminal diproline and charge group effects on the stabilization of helical conformation in alanine-based short peptides: CD studies with water and methanol as solvent. J Pept Sci 2017; 23:431-437. [PMID: 28425159 DOI: 10.1002/psc.3005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Revised: 03/17/2017] [Accepted: 03/20/2017] [Indexed: 12/25/2022]
Abstract
Protein folding problem remains a formidable challenge as main chain, side chain and solvent interactions remain entangled and have been difficult to resolve. Alanine-based short peptides are promising models to dissect protein folding initiation and propagation structurally as well as energetically. The effect of N-terminal diproline and charged side chains is assessed on the stabilization of helical conformation in alanine-based short peptides using circular dichroism (CD) with water and methanol as solvent. A1 (Ac-Pro-Pro-Ala-Lys-Ala-Lys-Ala-Lys-Ala-NH2 ) is designed to assess the effect of N-terminal homochiral diproline and lysine side chains to induce helical conformation. A2 (Ac-Pro-Pro-Glu-Glu-Ala-Ala-Lys-Lys-Ala-NH2 ) and A3 (Ac-dPro-Pro-Glu-Glu-Ala-Ala-Lys-Lys-Ala-NH2 ) with N-terminal homochiral and heterochiral diproline, respectively, are designed to assess the effect of Glu...Lys (i, i + 4) salt bridge interactions on the stabilization of helical conformation. The CD spectra of A1, A2 and A3 in water manifest different amplitudes of the observed polyproline II (PPII) signals, which indicate different conformational distributions of the polypeptide structure. The strong effect of solvent substitution from water to methanol is observed for the peptides, and CD spectra in methanol evidence A2 and A3 as helical folds. Temperature-dependent CD spectra of A1 and A2 in water depict an isodichroic point reflecting coexistence of two conformations, PPII and β-strand conformation, which is consistent with the previous studies. The results illuminate the effect of N-terminal diproline and charged side chains in dictating the preferences for extended-β, semi-extended PPII and helical conformation in alanine-based short peptides. The results of the present study will enhance our understanding on stabilization of helical conformation in short peptides and hence aid in the design of novel peptides with helical structures. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.
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Affiliation(s)
- Bhupesh Goyal
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.,Department of Chemistry, School of Basic and Applied Sciences, Sri Guru Granth Sahib World University, Fatehgarh Sahib, 140406, Punjab, India
| | - Kinshuk Raj Srivastava
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.,Life Sciences Institute, University of Michigan, Ann Arbor, MI, 48105, USA
| | - Susheel Durani
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
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Shuaib S, Goyal B. Scrutiny of the mechanism of small molecule inhibitor preventing conformational transition of amyloid-β 42 monomer: insights from molecular dynamics simulations. J Biomol Struct Dyn 2017; 36:663-678. [PMID: 28162045 DOI: 10.1080/07391102.2017.1291363] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Alzheimer's disease (AD) is a progressive neurodegenerative disorder that is characterized by loss of intellectual functioning of brain and memory loss. According to amyloid cascade hypothesis, aggregation of amyloid-β42 (Aβ42) peptide can generate toxic oligomers and their accumulation in the brain is responsible for the onset of AD. In spite of carrying out a large number of experimental studies on inhibition of Aβ42 aggregation by small molecules, the detailed inhibitory mechanism remains elusive. In the present study, comparable molecular dynamics (MD) simulations were performed to elucidate the inhibitory mechanism of a sulfonamide inhibitor C1 (2,5-dichloro-N-(4-piperidinophenyl)-3-thiophenesulfonamide), reported for its in vitro and in vivo anti-aggregation activity against Aβ42. MD simulations reveal that C1 stabilizes native α-helix conformation of Aβ42 by interacting with key residues in the central helix region (13-26) with hydrogen bonds and π-π interactions. C1 lowers the solvent-accessible surface area of the central hydrophobic core (CHC), KLVFF (16-20), that confirms burial of hydrophobic residues leading to the dominance of helical conformation in the CHC region. The binding free energy analysis with MM-PBSA demonstrates that Ala2, Phe4, Tyr10, Gln15, Lys16, Leu17, Val18, Phe19, Phe20, Glu22, and Met35 contribute maximum to binding free energy (-43.1 kcal/mol) between C1 and Aβ42 monomer. Overall, MD simulations reveal that C1 inhibits Aβ42 aggregation by stabilizing native helical conformation and inhibiting the formation of aggregation-prone β-sheet conformation. The present results will shed light on the underlying inhibitory mechanism of small molecules that show potential in vitro anti-aggregation activity against Aβ42.
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Affiliation(s)
- Suniba Shuaib
- a Department of Chemistry , School of Basic and Applied Sciences, Sri Guru Granth Sahib World University , Fatehgarh Sahib 140406 , Punjab , India
| | - Bhupesh Goyal
- a Department of Chemistry , School of Basic and Applied Sciences, Sri Guru Granth Sahib World University , Fatehgarh Sahib 140406 , Punjab , India
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Goyal D, Shuaib S, Mann S, Goyal B. Rationally Designed Peptides and Peptidomimetics as Inhibitors of Amyloid-β (Aβ) Aggregation: Potential Therapeutics of Alzheimer's Disease. ACS COMBINATORIAL SCIENCE 2017; 19:55-80. [PMID: 28045249 DOI: 10.1021/acscombsci.6b00116] [Citation(s) in RCA: 162] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Alzheimer's disease (AD) is a progressive neurodegenerative disease with no clinically accepted treatment to cure or halt its progression. The worldwide effort to develop peptide-based inhibitors of amyloid-β (Aβ) aggregation can be considered an unplanned combinatorial experiment. An understanding of what has been done and achieved may advance our understanding of AD pathology and the discovery of effective therapeutic agents. We review here the history of such peptide-based inhibitors, including those based on the Aβ sequence and those not derived from that sequence, containing both natural and unnatural amino acid building blocks. Peptide-based aggregation inhibitors hold significant promise for future AD therapy owing to their high selectivity, effectiveness, low toxicity, good tolerance, low accumulation in tissues, high chemical and biological diversity, possibility of rational design, and highly developed methods for analyzing their mode of action, proteolytic stability (modified peptides), and blood-brain barrier (BBB) permeability.
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Affiliation(s)
- Deepti Goyal
- Department of Chemistry,
School of Basic and Applied Sciences, Sri Guru Granth Sahib World University, Fatehgarh Sahib-140406, Punjab, India
| | - Suniba Shuaib
- Department of Chemistry,
School of Basic and Applied Sciences, Sri Guru Granth Sahib World University, Fatehgarh Sahib-140406, Punjab, India
| | - Sukhmani Mann
- Department of Chemistry,
School of Basic and Applied Sciences, Sri Guru Granth Sahib World University, Fatehgarh Sahib-140406, Punjab, India
| | - Bhupesh Goyal
- Department of Chemistry,
School of Basic and Applied Sciences, Sri Guru Granth Sahib World University, Fatehgarh Sahib-140406, Punjab, India
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Goyal B, Srivastava KR, Durani S. Examination of the Effect of N-terminal Diproline and Charged Side Chains on the Stabilization of Helical Conformation in Alanine-based Short Peptides: A Molecular Dynamics Study. ChemistrySelect 2016. [DOI: 10.1002/slct.201601381] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Bhupesh Goyal
- Department of Chemistry; Indian Institute of Technology Bombay, Powai; Mumbai-400076 India
- Department of Chemistry; School of Basic and Applied Sciences; Sri Guru Granth Sahib World University, Fatehgarh; Sahib-140406, Punjab India
| | - Kinshuk Raj Srivastava
- Department of Chemistry; Indian Institute of Technology Bombay, Powai; Mumbai-400076 India
- Life Sciences Institute; University of Michigan; Ann Arbor, MI USA 48105
| | - Susheel Durani
- Department of Chemistry; Indian Institute of Technology Bombay, Powai; Mumbai-400076 India
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