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The Chaperone Action of Bovine Milk αS1- And αS2-caseins and Their Associated Form αS-casein

The Chaperone Action of Bovine Milk αS1- And αS2-caseins and Their Associated Form αS-casein

Teresa M Treweek, David C Thorn, William E Price, John A Carver

Arch Biochem Biophys. 2011 Jun 1;510(1):42-52.

PMID: 21457703

Abstract:

α(S)-Casein, the major milk protein, comprises α(S1)- and α(S2)-casein and acts as a molecular chaperone, stabilizing an array of stressed target proteins against precipitation. Here, we report that α(S)-casein acts in a similar manner to the unrelated small heat-shock proteins (sHsps) and clusterin in that it does not preserve the activity of stressed target enzymes. However, in contrast to sHsps and clusterin, α-casein does not bind target proteins in a state that facilitates refolding by Hsp70. α(S)-Casein was also separated into α- and α-casein, and the chaperone abilities of each of these proteins were assessed with amorphously aggregating and fibril-forming target proteins. Under reduction stress, all α-casein species exhibited similar chaperone ability, whereas under heat stress, α-casein was a poorer chaperone. Conversely, α(S2)-casein was less effective at preventing fibril formation by modified κ-casein, whereas α- and α(S1)-casein were comparably potent inhibitors. In the presence of added salt and heat stress, α(S1)-, α- and α(S)-casein were all significantly less effective. We conclude that α(S1)- and α-casein stabilise each other to facilitate optimal chaperone activity of α(S)-casein. This work highlights the interdependency of casein proteins for their structural stability.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP9000719-C	α-Casein from bovine milk		9000-71-9	Price

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