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

A A Moosavi-Movahedi, H Rajabzadeh, M Amani, D Nourouzian, K Zare, H Hadi, A Sharifzadeh, N Poursasan, F Ahmad, N Sheibani

Index: Int. J. Biol. Macromol. 49(4) , 616-21, (2011)

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Abstract

An important factor in medicine and related industries is the use of chaperones to reduce protein aggregation. Here we show that chaperone ability is induced in β-casein by modification of its acidic residues using Woodward's Reagent K (WRK). Lysozyme at pH 7.2 was used as a target protein to study β-casein chaperone activities. The mechanism for chaperone activity of the modified β-casein was determined using UV-vis absorbencies, fluorescence spectroscopy, differential scanning calorimetry and theoretical calculations. Our results indicated that the β-casein destabilizes the lysozyme and increases its aggregation rate. However, WRK-ring sulfonate anion modifications enhanced the hydrophobicity of β-casein resulting in its altered net negative charge upon interactions with lysozyme. The reversible stability of lysozyme increased in the presence of WRK-modified β-casein, and hence its aggregation rate decreased. These results demonstrate the enhanced chaperone activity of modified β-casein and its protective effects on lysozyme refolding.Copyright © 2011 Elsevier B.V. All rights reserved.