| 1. |
- Friedman, Ran, et al.
(författare)
-
Surfactant Effects on Amyloid Aggregation Kinetics
- 2011
-
Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 0022-2836 .- 1089-8638. ; 414, s. 303-312
-
Tidskriftsartikel (refereegranskat)abstract
- There is strong experimental evidence of the influence of surfactants (e.g., fatty acids) on the kinetics of amyloid fibril formation. However, the structures of mixed assemblies and interactions between surfactants and fibril-forming peptides are still not clear. Here, coarse-grained simulations are employed to study the aggregation kinetics of amyloidogenic peptides in the presence of amphiphilic lipids. The simulations show that the lower the fibril formation propensity of the peptides, the higher the influence of the surfactants on the peptide self-assembly kinetics. In particular, the lag phase of weakly aggregating peptides increases because of the formation of mixed oligomers, which are promoted by hydrophobic interactions and favorable entropy of mixing. A transient peak in the number of surfactants attached to the growing fibril is observed before reaching the mature fibril in some of the simulations. This peak originates from transient fibrillar defects consisting of exposed hydrophobic patches on the fibril surface, which provide a possible explanation for the temporary maximum of fluorescence observed sometimes in kinetic traces of the binding of small-molecule dyes to amyloid fibrils.
|
|
| 2. |
- Friedman, Ran, et al.
(författare)
-
Wild type and mutants of the HET-s(218-289) prion show different flexibility at fibrillar ends : A simulation study
- 2014
-
Ingår i: Proteins. - : Wiley. - 0887-3585 .- 1097-0134. ; 82:3, s. 399-404
-
Tidskriftsartikel (refereegranskat)abstract
- The C-terminal segment (residues 218–289) of the HET-s protein of the filamentous fungus Podosporina anserina is a prion-forming domain. The structural model of the HET-s(218–289) amyloid fibril based on solid-state nuclear magnetic resonance (NMR) restraints shows a β solenoid topology which is comprised of a β-sheet core and interconnecting loops. For the single-point mutants Phe286Ala and Trp287Ala, slower aggregation rates in vitro and loss of prionic infectivity have been reported recently. Here we have used molecular dynamics to compare the flexibility of the mutants and wild type. The simulations, initiated from a trimeric aggregate extracted from the NMR structural model, show structural stability on a 100-ns time scale for wild type and mutants. Analysis of the fluctuations along the simulations reveals that the mutants are less flexible than the wild type in the C-terminal segment at only one of the two external monomers. Analysis of interaction energy and buried accessible surface indicates that residue Phe286 in particular is stabilized in the Trp287Ala mutant. The simulation results provide an atomistic explanation of the suggestion (based on indirect experimental evidence) that flexibility at the protofibril end(s) is required for fibril elongation. Moreover, they provide further evidence that the growth of the HET-s amyloid fibril is directional.
|
|
| 3. |
- Herrmann, Uli S., et al.
(författare)
-
Structure-based drug design identifies polythiophenes as antiprion compounds
- 2015
-
Ingår i: Science Translational Medicine. - : AMER ASSOC ADVANCEMENT SCIENCE. - 1946-6234 .- 1946-6242. ; 7:299, s. 299ra123-
-
Tidskriftsartikel (refereegranskat)abstract
- Prions cause transmissible spongiform encephalopathies for which no treatment exists. Prions consist of PrPSc, a misfolded and aggregated form of the cellular prion protein (PrPC). We explore the antiprion properties of luminescent conjugated polythiophenes (LCPs) that bind and stabilize ordered protein aggregates. By administering a library of structurally diverse LCPs to the brains of prion-infected mice via osmotic minipumps, we found that antiprion activity required a minimum of five thiophene rings bearing regularly spaced carboxyl side groups. Solid-state nuclear magnetic resonance analyses and molecular dynamics simulations revealed that anionic side chains interacted with complementary, regularly spaced cationic amyloid residues of model prions. These findings allowed us to extract structural rules governing the interaction between LCPs and protein aggregates, which we then used to design a new set of LCPs with optimized binding. The new set of LCPs showed robust prophylactic and therapeutic potency in prion-infected mice, with the lead compound extending survival by greater than80% and showing activity against both mouse and hamster prions as well as efficacy upon intraperitoneal administration into mice. These results demonstrate the feasibility of targeted chemical design of compounds that may be useful for treating diseases of aberrant protein aggregation such as prion disease.
|
|
| 4. |
- Li, Yaozong, et al.
(författare)
-
Atomistic and Thermodynamic Analysis of N6-Methyladenosine (m6A) Recognition by the Reader Domain of YTHDC1
- 2021
-
Ingår i: Journal of Chemical Theory and Computation. - : American Chemical Society (ACS). - 1549-9618 .- 1549-9626. ; 17:2, s. 1240-1249
-
Tidskriftsartikel (refereegranskat)abstract
- N6-Methyladenosine (m6A) is the most frequent modification in eukaryotic messenger RNA (mRNA) and its cellular processing and functions are regulated by the reader proteins YTHDCs and YTHDFs. However, the mechanism of m6A recognition by the reader proteins is still elusive. Here, we investigate this recognition process by combining atomistic simulations, site-directed mutagenesis, and biophysical experiments using YTHDC1 as a model. We find that the N6 methyl group of m6A contributes to the binding through its specific interactions with an aromatic cage (formed by Trp377 and Trp428) and also by favoring the association-prone conformation of m6A-containing RNA in solution. The m6A binding site dynamically equilibrates between multiple metastable conformations with four residues being involved in the regulation of m6A binding (Trp428, Met438, Ser378, and Thr379). Trp428 switches between two conformational states to build and dismantle the aromatic cage. Interestingly, mutating Met438 and Ser378 to alanine does not alter m6A binding to the protein but significantly redistributes the binding enthalpy and entropy terms, i.e., enthalpy–entropy compensation. Such compensation is reasoned by different entropy–enthalpy transduction associated with both conformational changes of the wild-type and mutant proteins and the redistribution of water molecules. In contrast, the point mutant Thr379Val significantly changes the thermal stability and binding capability of YTHDC1 to its natural ligand. Additionally, thermodynamic analysis and free energy calculations shed light on the role of a structural water molecule that synergistically binds to YTHDC1 with m6A and acts as the hub of a hydrogen-bond network. Taken together, the experimental data and simulation results may accelerate the discovery of chemical probes, m6A-editing tools, and drug candidates against reader proteins.
|
|
| 5. |
- Li, Yaozong, et al.
(författare)
-
Structural and Dynamic Insights into Redundant Function of YTHDF Proteins
- 2020
-
Ingår i: Journal of Chemical Information and Modeling. - : American Chemical Society (ACS). - 1549-9596 .- 1549-960X. ; 60:12, s. 5932-5935
-
Tidskriftsartikel (refereegranskat)abstract
- Three YTH-domain family proteins (YTHDF1, YTHDF2, and YTHDF3) recognize the N6-methyladenosine (m6A) modification of mRNA in cells. However, the redundancy of their cellular functions has been disputed. We investigate their interactions with m6A-containing RNA using X-ray crystallography and molecular dynamics (MD). The new X-ray structures and MD simulations show that the three proteins share identical interactions with the m6A-containing RNA and have similar intrinsic plasticity, thus evidencing the redundant roles of the three proteins in cellular functions.
|
|
| 6. |
- Li, Yaozong, et al.
(författare)
-
Structure-based design of ligands of the m6A-RNA reader YTHDC1
- 2022
-
Ingår i: European Journal of Medicinal Chemistry Reports. - : Elsevier. - 2772-4174. ; 5
-
Tidskriftsartikel (refereegranskat)abstract
- We report new chemical entities for disrupting the interactions between N6-methyladenosine (m6A) mRNA and its reader YT521-B homology-domain-containing protein 1 (YTHDC1). High-throughput docking was used to screen commercially available databases of small molecules, and molecular dynamics simulations were employed to evaluate the binding stability of m6A nucleotide analogues. The poses of 25 fragment-like new binders were confirmed by X-ray crystallography. The structure-based merging of two weak fragments resulted in a ligand-efficient binder (compound 6) which shows an equilibrium dissociation constant of 1.7 μM in isothermal titration calorimetry measurements and a ligand efficiency value of 0.66 kcal mol−1 nHA−1.
|
|
| 7. |
- Li, Yaozong, 1982-
(författare)
-
Understanding molecular mechanisms of protein tyrosine kinases by molecular dynamics and free energy calculations
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Insulin receptor kinase (IRK) and Insulin-like growth factor 1 receptor kinase (IGF-1RK) are two important members in the large class of tyrosine kinase receptors. They play pivotalroles in the regulation of glucose homeostasis, cell proliferation, differentiation, motility, andtransformation. Their dysfunctions are linked to diabetes, rheumatoid arthritis and many cancers.Although their regulatory mechanisms have been widely studied experimentally, the atomisticdetails are still poorly understood, especially for the influences caused by activation loop (A-loop)phosphorylation.Methods: Molecular dynamics (MD) and alchemical free energy simulations are carried out tounderstand mechanisms underlying the kinase proteins regulation and their thermodynamic basis.To capture a full picture about the entire kinase catalytic cycle, different functional steps areconsidered, i.e., conformational transition, substrate binding, phosphoryl transfer and productrelease. The effects of the A-loop phosphorylation on protein’s dynamics, structure, stability, andfree energy landscape are examined by various analysis methods, including principle componentanalysis (PCA), motion projection, dynamical network analysis and free energy perturbation.Results: The main findings are: 1) A-loop phosphorylation shifts the kinase conformationalpopulation to the active one by changing the electrostatic environments in the kinase apo form, 2)allosterically fine-tunes the orientation of the catalytic residues mediated by the >C-helix in thereactant and product binding states, and 3) thermodynamically favors the kinase catalysis presentedby a catalytic-cycle-mimic free energy landscape. An integrated view on the roles of A-loopphosphorylation in kinase allostery is developed by incorporating kinase’s dynamics, structuralinteractions, thermodynamics and free energy landscape. In addition, new soft-core potentials(Gaussian soft-core) and protocols are developed to conduct accurate and efficient alchemical freeenergy calculations.Conclusions: The entire catalytic cycle is examined by MD and free energy calculations andcomprehensive analyses are conducted. The findings from the studied kinases are general and canbe implemented to the other members in IRK family or even to more non-homologous familiesbecause of the conservation of the characteristic residues between their A-loop and >C-helix. Inaddition, the Gaussian soft-core potentials provide a new tool to perform alchemical free energycalculations in an efficient way.
|
|
| 8. |
- Meyer, Peter A., et al.
(författare)
-
Data publication with the structural biology data grid supports live analysis
- 2016
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- Access to experimental X-ray diffraction image data is fundamental for validation and reproduction of macromolecular models and indispensable for development of structural biology processing methods. Here, we established a diffraction data publication and dissemination system, Structural Biology Data Grid (SBDG; data. sbgrid. org), to preserve primary experimental data sets that support scientific publications. Data sets are accessible to researchers through a community driven data grid, which facilitates global data access. Our analysis of a pilot collection of crystallographic data sets demonstrates that the information archived by SBDG is sufficient to reprocess data to statistics that meet or exceed the quality of the original published structures. SBDG has extended its services to the entire community and is used to develop support for other types of biomedical data sets. It is anticipated that access to the experimental data sets will enhance the paradigm shift in the community towards a much more dynamic body of continuously improving data analysis.
|
|
| 9. |
- Milardi, Danilo, et al.
(författare)
-
Proteostasis of Islet Amyloid Polypeptide : A Molecular Perspective of Risk Factors and Protective Strategies for Type II Diabetes
- 2021
-
Ingår i: Chemical Reviews. - : American Chemical Society (ACS). - 0009-2665 .- 1520-6890. ; 121:3, s. 1845-1893
-
Forskningsöversikt (refereegranskat)abstract
- The possible link between hIAPP accumulation and β-cell death in diabetic patients has inspired numerous studies focusing on amyloid structures and aggregation pathways of this hormone. Recent studies have reported on the importance of early oligomeric intermediates, the many roles of their interactions with lipid membrane, pH, insulin, and zinc on the mechanism of aggregation of hIAPP. The challenges posed by the transient nature of amyloid oligomers, their structural heterogeneity, and the complex nature of their interaction with lipid membranes have resulted in the development of a wide range of biophysical and chemical approaches to characterize the aggregation process. While the cellular processes and factors activating hIAPP-mediated cytotoxicity are still not clear, it has recently been suggested that its impaired turnover and cellular processing by proteasome and autophagy may contribute significantly toward toxic hIAPP accumulation and, eventually, β-cell death. Therefore, studies focusing on the restoration of hIAPP proteostasis may represent a promising arena for the design of effective therapies. In this review we discuss the current knowledge of the structures and pathology associated with hIAPP self-assembly and point out the opportunities for therapy that a detailed biochemical, biophysical, and cellular understanding of its aggregation may unveil.
|
|
| 10. |
- Nai, Francesco, et al.
(författare)
-
Fragment Ligands of the m6A-RNA Reader YTHDF2
- 2022
-
Ingår i: ACS Medicinal Chemistry Letters. - : American Chemical Society (ACS). - 1948-5875 .- 1948-5875. ; 13:9, s. 1500-1509
-
Tidskriftsartikel (refereegranskat)abstract
- We report 17 small-molecule ligands that compete with N6-methyladenosine (m6A) for binding to the m6A-reader domain of YTHDF2 (YT521-B homology domain family 2). We determined their binding mode at high resolution by X-ray crystallography and quantified their affinity by a fluorescence-based binding assay. 6-Cyclopropyluracil and a pyrazolopyrimidine derivative have favorable ligand efficiencies of 0.47 and 0.38 kcal mol-1 per non-hydrogen atom, respectively. They represent useful starting points for hit optimization.
|
|
