Effect of salts and sodium dodecyl sulfate on chaperone activity of camel αS1-CN: Insulin as the target protein

In this study camel alpha S-1-casein (alpha S-1-CN) was purified, using a two-step purification procedure. The antiaggregation (chaperone-like) ability of the purified protein sample was examined in a wide range of experimental conditions and at different concentrations of camel alpha S-1-CN, in the presence of salts and sodium dodecyl sulfate (SIDS). To examine chaperone-like activity of camel alpha S-1-CN, bovine pancreatic insulin was used as the target protein. Insulin aggregation performed chemically in the presence of 20 mM dithiotreitol (DTT) and was studied at 360 nm wavelength by UV-vis spectro photometer. Camel alpha S-1-CN exhibited a dose-dependent chaperone-like activity as the molar ratios of chaperone/target protein varied between 0 and 0.07. The presence of salts or surfactants changing the protein properties had an influence on chaperone capacity of camel alpha S-1-CN. The results of UV-visible and fluorimetric measurements indicated that the salts neutralize the chaperone-like activity of casein due to dehydration effect and the increased association and aggregation of proteins, while SDS plays a role as chaperone and chaperone-like properties of camel alpha S-1-CN enhanced in the presence of SIDS due to the binding of the hydrophobic tail of SDS and alpha S-1-CN to the exposed hydrophobic sites of insulin strongly preventing aggregation of insulin. (C) 2009 Elsevier B.V. All rights reserved.