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

It is well accepted that porphyrins related to heme, are effectively able to act as pharmaceutical. For instance, they were found to interfere with the aggregation of beta-amyloid peptide. In present study, the influence of heme concentration on the amyloid-type aggregation of ovalbumin was investigated. We provided experimental evidence of heme's prevention of ovalbumin aggregation in the heat-denaturation process using spectroscopic measurements. Different types of interactions were suggested to be involved in heme-ovalbumin amyloid communication. Since the consequence of heme-attenuated fibrillogenesis is yet to be identified, additional data on chaperoning role of heme may help us to manage amyloid aggregation processes.

Appraisal of casein's inhibitory effects on aggregation accompanying carbonic anhydrase refolding and heat-induced ovalbumin fibrillogenesis.

It is well accepted that whole casein and its purified major components, due to their chaperone-like activity, are able to suppress the thermal and chemical aggregation of several substrate proteins. In this study, we set out to determine whether whole and beta-casein are able to prevent (or attenuate) aggregation accompanying refolding of chemically denatured carbonic anhydrase or to recover lost biological activity after its denaturation. Additionally, we showed attenuated heat-induced fibrillar aggregation of egg white ovalbumin in the presence of these commonly occurring unfolded proteins, as molecular chaperones. Also, the extent, rate and order of aggregation, in the presence and absence of aggregation suppressors, were compared. Although beta-casein did not prevent aggregation as strong as whole casein, both chaperones were efficient not only in suppressing the aggregation extent of denatured carbonic anhydrase, but also in delaying elongation process of amyloid fibril formation with no effect on nucleation phase.

Study of cosolvent-induced alpha-chymotrypsin fibrillogenesis: does protein surface hydrophobicity trigger early stages of aggregation reaction?

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.