The Effect of Arg on the Structure Perturbation and Chaperone Activity of α-Crystallin in the Presence of the Crowding Agent, Dextran

Abstract

α-Crystallin is a protein that is expressed at high levels in all vertebrate eye lenses. It has a molecular weight of 20 kDa and is composed of two subunits: αA and αB. α-Crystallin is a member of the small heat shock protein (sHsps) family that has been shown to prevent protein aggregation. Small molecules are organic compounds that have low molecular weight (<800 Da). Arginin (Arg) is a small molecule and has been shown to prevent protein aggregation through interaction with partially folded intermediates. In this study, the effect of Arg on the chaperone activity of α-crystallin in the presence of dextran, as a crowding agent, against ordered and disordered aggregation of different target proteins (α-lactalbumin, ovotransferrin, and catalase) has been investigated. The experiments were done using visible absorption spectroscopy, ThT-binding assay, fluorescence spectroscopy, and CD spectroscopy. The results showed that in amorphous aggregation and amyloid fibril formation, both in the presence and absence of dextran, Arg had a positive effect on the chaperone action of α-crystallin. However, in the presence of dextran, the effect of Arg on the chaperone ability of α-crystallin was less than in its absence. Thus, our result suggests that crowding interior media decreases the positive effect of Arg on the chaperone ability of α-crystallin. This is a very important issue, since we are trying to find a mechanism to protect living cells against the toxic effect of protein aggregation.

Conditions Governing Food Protein Amyloid Fibril Formation. Part II: Milk and Legume Proteins

“…ThT fluorescence measurements have shown that the rate and extent of amyloid formation of α‐LA at neutral pH in the presence of dithiothreitol can be increased with the crowding agent dextran. In contrast, α‐casein, α‐crystallin, and arginine can reduce the extent of its fibril formation (Ghahghaei & Mohammadian, ; Ghahghaei et al., ). Oleic acid completely inhibits fibril formation at pH 4.5, but does not have such effect at pH 2.0 or 3.0 (Yang et al., ).…”

The Effect of Ficol on α-lactalbumin Aggregation

“…In order to investigate the effect of macromolecular crowding, ficol, on the aggregation of α-lactalbumin. ThT binding assay showed that the fluorescence intensity of ThT of reduced α-lactalbumin increased at pH 7.4 (11). The ThT intensity of α-lactalbumin decreased in presence of ficol which means ficol could suppress amyloid formation of a-lactalbumin.…”

Hsp90 Structure and Function in Cancer

“…Several detailed studies are available that address the structural and molecular biology and function of HSPs in general (22)(23)(24)(25)(26) and HSP90 in particular (27).…”