Study of Cosolvent-Induced α-Chymotrypsin Fibrillogenesis: Does Protein Surface Hydrophobicity Trigger Early Stages of Aggregation Reaction?

Abstract

The misfolding of specific proteins is often associated with their assembly into fibrillar aggregates, commonly termed amyloid fibrils. Despite the many efforts expended to characterize amyloid formation in vitro, there is no deep knowledge about the environment (in which aggregation occurs) as well as mechanism of this type of protein aggregation. Alpha-chymotrypsin was recently driven toward amyloid aggregation by the addition of intermediate concentrations of trifluoroethanol. In the present study, approaches such as turbidimetric, thermodynamic, intrinsic fluorescence and quenching studies as well as chemical modification have been successfully used to elucidate the underlying role of hydrophobic interactions (involved in early stages of amyloid formation) in alpha-chymotrypsin-based experimental system.

Molten Globule of Hemoglobin Proceeds into Aggregates and Advanced Glycated End Products

“…Trp residues in native Hb impart the least accessibility to acryalmide quencher. The K SV values of Hb at 20% and 70% glyoxal were higher as compared to native Hb [28]. This indicates that Trp residues in molten globule and aggregates possess much accessibility to the quencher due to the greater distance between Trp residues and heme group.…”

Appraisal of role of the polyanionic inducer length on amyloid formation by 412-residue 1N4R Tau protein: A comparative study

“…Need to further insight in this regard, led us to evaluate the potential involved interactions, at the early stages of polyaninon-induced Tau fibrillogenesis. When ANS binds to solvent-exposed hydrophobic clusters, it generates a remarkable increase in its fluorescence intensity and a blue shift of its maximum emission wavelength[53,54]. As it is evident fromFig.…”

“…Moreover, with regard to kinetic competition between correct folding and undesired aggregation[52]; it appears reasonable that hydrophobic effects should be also involved in unproductive protein misfolding and aggregation. In that respect, several authors[53] have considered a key role for the hydrophobic interactions in the early stages of amyloid formation. Need to further insight in this regard, led us to evaluate the potential involved interactions, at the early stages of polyaninon-induced Tau fibrillogenesis.…”

Possible peroxidase active site environment in amyloidogenic proteins: Native monomer or misfolded-oligomer; which one is susceptible to the enzymatic activity, with contribution of heme?

“…To investigate whether intact BLG and protease-treated protein samples were converted to amyloid-like fibrils, ThT-based fluorimetric method was employed [9,16]. As discussed earlier, native ␤-lactoglobulin has been found to be converted readily to amyloid fibrils under various experimental conditions [9 and references therein].…”

“…, the fluorescence intensity of ThT upon binding to the fibrillar Incubation Time (min) ThT Fluorescence (a.u.Kinetics of BLG (amyloid) aggregation as followed by ThT fluorescence changes at 482 nm[16]. Data shown are representative example of three independent experiments.…”