Insights into the mechanism of how Morin suppresses amyloid fibrillation of hen egg white lysozyme

Impact of Sinapic Acid on Bovine Serum Albumin Thermal Stability

The thermal stability of bovine serum albumin (BSA) in Tris buffer, as well as the effect of sinapic acid (SA) on protein conformation were investigated via calorimetric (differential scanning microcalorimetry-μDSC), spectroscopic (dynamic light scattering-DLS; circular dichroism-CD), and molecular docking approaches. μDSC data revealed both the denaturation (endotherm) and aggregation (exotherm) of the protein, demonstrating the dual effect of SA on protein thermal stability. With an increase in ligand concentration, (i) protein denaturation shifts to a higher temperature (indicating native form stabilization), while (ii) the aggregation process shifts to a lower temperature (indicating enhanced reactivity of the denatured form). The stabilization effect of SA on the native structure of the protein was supported by CD results. High temperature (338 K) incubation induced protein unfolding and aggregation, and increasing the concentration of SA altered the size distribution of the protein population, as DLS measurements demonstrated. Complementary information offered by molecular docking allowed for the assessment of the ligand binding within the Sudlow's site I of the protein. The deeper insight into the SA-BSA interaction offered by the present study may serve in the clarification of ligand pharmacokinetics and pharmacodynamics, thus opening paths for future research and therapeutic applications.

Myricetin and morin hydrate inhibit amyloid fibril formation of bovine α-lactalbumin (BLA)

Amyloid fibrils are self-assembled aggregates of proteins and peptides that can lead to a broad range of diseases called amyloidosis. So far, no definitive and approved treatment to target directly amyloid fibrils has been introduced. Nevertheless, the search for small molecules with ability to inhibit and suppress fibril formation is an active and promising area of the research. Herein, the binding interactions and inhibitory effects of myricetin and morin hydrate on the in vitro fibrillation of bovine α-lactalbumin (BLA) have been investigated. The intrinsic fluorescence of BLA was quenched by myricetin and morin hydrate through combination of the static and dynamic quenching along with non-radiative Förster energy transfer mechanisms. The binding of these two flavonoids to BLA were not accompanied by major alteration in the conformation of BLA as evidenced by CD studies. The results of the fluorescence quenching analyses indicated almost the same binding affinities of myricetin and morin hydrate toward BLA (Kb ~ 106 M-1). However, the results of thioflavin T (ThT) assays showed that myricetin is a stronger inhibitor against BLA fibrillation compared to morin hydrate.

Inhibition of the formation of lysozyme fibrillar assemblies by the isoquinoline alkaloid coralyne

The isoquinoline alkaloid coralyne can efficiently attenuate fibrillogenesis in lysozyme.

Inhibition of Amyloid Fibrillation of HEWL by 4-Methylcoumarin and 4-Methylthiocoumarin Derivatives

BACKGROUND

Several human diseases like Parkinson's, Alzheimer's disease, and systemic amyloidosis are associated with the misfolding and aggregation of protein molecules.

OBJECTIVE

The present study demonstrated the comparison of 4-methyl coumarin and 4-methylthiocoumarin derivative for their anti-amyloidogenic and disaggregation activities. The hen egg-white lysozyme is used as a model system to study protein aggregation and disaggregation under in vitro conditions.

METHODS

Techniques used in the study were Thioflavin T fluorescence assay, intrinsic fluorescence assay, circular dichroism, transmission electron microscopy, and molecular dynamics.

RESULTS

Fifteen compounds were screened for their anti-amyloidogenic and disaggregation potential. Six compounds significantly inhibited the fibril formation, whereas ten compounds showed disaggregation property of pre-formed fibrils. Under in vitro conditions, the compound C3 and C7 showed significant inhibition of fibril formation in a concentration-dependent manner as compared to control. C3 and C7 demonstrated 93% and 76% inhibition of fibril formation, respectively. Furthermore, C3 and C7 exhibited 83% and 76% disaggregation activity, respectively, of pre-formed HEWL fibrils at their highest concentration. These anti-amyloidogenic and disaggregation potential of C3 and C7 were validated by intrinsic fluorescence, CD, molecular dynamics, and TEM study.

DISCUSSION

4-methylthiocoumarins derivatives have shown better anti-amyloidogenic activity as compared to 4-methylcoumarin derivatives for both amyloid formation as well as disaggregation of preformed amyloid fibrils. Structurally, the derivatives of 4-methylthiocoumarins (C3 and C7) contain thio group on 2nd position that might be responsible for anti-amyloidogenic activity as compared to 4- methylcoumarin derivatives (C2 and C4).

CONCLUSION

C3 and C7 are novel 4-methylthiocoumarin derivatives that can be used as a lead for alleviation and symptoms associated with protein aggregation disorders.

Interaction of anticancer drug pinostrobin with lysozyme: a biophysical and molecular docking approach

Communicated by Ramaswamy H. Sarma.

Inhibition of HEWL fibril formation by taxifolin: Mechanism of action

Among therapeutic approaches for amyloid-related diseases, attention has recently turned to the use of natural products as effective anti-aggregation compounds. Although a wealth of in vitro and in vivo evidence indicates some common inhibitory activity of these compounds, they don't generally suggest the same mechanism of action. Here, we show that taxifolin, a ubiquitous bioactive constituent of foods and herbs, inhibits formation of HEWL amyloid fibrils and their related toxicity by causing formation of very large globular, chain-like aggregates. A range of amyloid-specific techniques were employed to characterize this process. We found that taxifolin exerts its effect by binding to HEWL prefibrillar species, rather than by stabilizing the molecule in its native-like state. Furthermore, it's binding results in diverting the amyloid pathway toward formation of very large globular, chain-like aggregates with low β-sheet content and reduced solvent-exposed hydrophobic patches. ThT fluorescence measurements show that the binding capacity of taxifolin is significantly reduced, upon generation of large protofibrillar aggregates at the end of growth phase. We believe these results may help design promising inhibitors of protein aggregation for amyloid-related diseases.