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

Protein-Protein interactions leading to aggregation: Perspectives on mechanism, significance and control

“…Variation in aggregation-preventing effect has been observed, depending on the polarity of N-terminal region of casein [104], or more generally, on its net charge, and surface hydrophobicity which was demonstrated for camel and bovine caseins [105,106]. In one study involving yeast hexokinase B, the presence of casein and its subsequent removal by cyclodextrin was effective in protecting the enzyme from aggregation and denaturation, presumably by a "chaperone-assisted refolding" mechanism [107].…”

Acidic residue modifications restore chaperone activity of β-casein interacting with lysozyme

“…There is a short N-terminal hydrophilic polar domain in ␤-casein chain, which carries most of the protein's net charge (mainly negative), and a prominent C-terminal hydrophobic domain [12,13]. Recently, a novel function for ␤-casein has been reported, namely a molecular chaperone that protects many proteins against heat and chemical induced aggregation [14][15][16][17]. The ␤-casein hydrophilic and hydrophobic domains enhance solubility in aqueous medium and allow binding of hydrophilic molecules, respectively [18,19].…”

Dual behavior of sodium dodecyl sulfate as enhancer or suppressor of insulin aggregation and chaperone-like activity of camel αS1-casein

“…Thus, the binding of hydrophobic tail of SDS to the exposed hydrophobic sites of insulin could suppress insulin aggregation. In fact as previously reported, the first interaction between SDS and protein possesses electrostatic characteristics followed by the hydrophobic interactions leading to gross protein conformational changes [34]. Thus, the hydrophobic tail of SDS plays a crucial function in its unfolding properties [34].…”

“…The interactions between SDS (40 M) and camel ␣S 1 -casein (␣S 1 -CN) at 37 • C has been previously reported [34]. SDS enhanced chaperone-like activities and properties of camel ␣S 1 -CN.…”

“…SDS contains a negatively charged head group and a hydrophobic tail and, consequently its impact on protein conformation is highly dependent on its concentration [34]. SDS may induce conformational changes in insulin, either via electrostatic interactions between charged head groups and the charged residues in insulin structure or via the hydrophobic interaction between the hydrophobic tail of the molecule and the hydrophobic parts of insulin.…”