Influence of trehalose on the molecular chaperone activity of p26, a smallheat shock/alpha-crystallin protein

Encysted embryos of the primitive crustacean Artemia franciscana are among the most resistant of all multicellular eukaryotes to environmental stress, in part due to massive amounts of a small heat shock/alpha -crystallin pro tein (p26) that acts as a molecular chaperone. These embryos also contain v ery large amounts of the disaccharide trehalose, well known for its ability to protect macromolecules and membranes against damage due to water remova l and temperature extremes. Therefore, we looked for potential interactions between trehalose and p26 in the protection of a model substrate, citrate synthase (CS), against heat denaturation and aggregation and in the restora tion of activity after heating in vitro. Both trehalose and p26 decreased t he aggregation and irreversible inactivation of CS at 43 degreesC. At appro ximate physiological concentrations (0.4 M), trehalose did not interfere wi th the ability of p26 to assist in the reactivation of CS after heating, bu t higher concentrations (0.8 M) were inhibitory. We also showed that CS and p26 interact physically during heating and that trehalose interferes with complex formation and disrupts CS-p26 complexes that form at high temperatu res. We suggest from these results that trehalose may act as a "release fac tor," freeing folding intermediates of CS that p26 can chaperone to the nat ive state. Trehalose and p26 can act synergistically in vitro, during and a fter thermal stress, suggesting that these interactions also occur in vivo.