Chaperone-like activity of heme group against amyloid-like fibril formation by hen egg ovalbumin: Possible mechanism of action

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?

“…Amyloid fibril aggregation is generally preceded by conformational changes in the native fold of disease-related proteins (such as A␤) and similarly, its formation by non-disease related proteins may be promoted by partially denaturing conditions. However, non-native protein oligomers are mainly created due to the conformational events involved in the early stages of fibrillogenesis [3,4,6,11].…”

“…Bovine ␣-crystallin was purified according to our earlier work [6]. Beta-Lactoglobulin (BLG) as well as ovalbumin purification and protein determination, were performed according to our earlier works [6,9,11]. All the experiments were performed in triplicate.…”

“…Immediately, the increase in the turbidity was followed by measuring the absorbance at 400 nm as a function of time relative to the appropriate blank [9]. Ovalbumin samples were also heated to 80 • C in buffer containing 20 mM sodium phosphate, 1-2 mg/ml protein, pH 7.2, on a thermostatic serological water bath for the specified durations while they were being gently stirred [11]. Aggregate amounts are expressed as a monomer-equivalent concentration, which was estimated from the concentration of the original protein solutions.…”

“…As discussed earlier, different proteins have been found to Changes to the fluorescence of ThT were used to determine the level of ovalbumin aggregation as described in [11]. The fluorescence signal of ThT, expressed in arbitrary units, resulting from ThT binding to ovalbumin aggregates declines rapidly, upon incubation with heme.…”

“…The structures visualization and figures generation were performed with different viewers. Further details are given in the "Materials and methods" and "Results" sections of [6,11].…”