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Updated: Jun 22, 2026

Detection of the pH-dependent Activity of Escherichia coli Chaperone HdeB In Vitro and In Vivo
Published on: October 23, 2016
Dephosphorylation of alpha(s)- and beta-caseins and its effect on chaperone activity: a structural and functional
Tomas Koudelka1, Peter Hoffmann, John A Carver
1School of Chemistry and Physics, The University of Adelaide, Adelaide, South Australia 5005, Australia.
Abstract:
Milk casein proteins can act as molecular chaperones: under conditions of stress, such as elevated temperature, molecular chaperones stabilize proteins from unfolding, aggregating, and precipitating. In this study, alpha(s)- and beta-caseins were dephosphorylated using alkaline phosphatase. A structural and functional investigation was undertaken to determine the effect of dephosphorylation on the chaperone activity of alpha(s)- and beta-caseins against two types of protein misfolding, i.e., amorphous aggregation and amyloid fibril assembly. The dephosphorylation of alpha(s)- and beta-caseins resulted in a decrease in the chaperone efficiency against both heat- and reduction-induced amorphously aggregating target proteins. In contrast, dephosphorylation had no effect on the chaperone activity of alpha(s)- and beta-caseins against the amyloid-forming target protein kappa-casein. Circular dichroism and fluorescence spectroscopic data indicated that the loss of negative charge associated with dephosphorylation led to an increase in ordered structure of alpha(s)- and beta-caseins. It is concluded that the flexible, dynamic, and relatively unstructured and amphiphatic nature of alpha(s)- and beta-caseins is important in their chaperone action.
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