You can't unfry an egg-or maybe you can. Researchers from the Howard Hughes Medical Institute at the University of Chicago report in the July 10 issue of Cell that a powerful combination of heat shock proteins (Hsps) can return aggregated proteins, until now thought to be permanently entangled, to their functional, native states.
Previously, scientists thought that Hsps could only prevent proteins from aggregating as temperatures rise. But now, Susan Lindquist, Ph.D., and colleague John Glover, Ph.D., have shown that protein snarls can actually be rescued by Hsp104 with the assistance of two other heat shock proteins.
Heat is a protein's enemy. As an egg fries, its proteins, which are made of chains of molecules called amino acids precisely folded into spirals, loops and sheets, begin to loose their shape. Sticky bits from the interior of the protein get exposed, and adhere to each other, forming disordered globs, or aggregates (this is why egg whites change from a clear liquid-like state to a white solid). In the body, heat stress can do the same thing to proteins, making them dysfunctional.
When exposed to sudden shifts in temperature, all organisms make heat shock proteins, otherwise known as chaperones, which protect (to some extent) against denaturation. The chaperone's job is to protect unfolded proteins from getting into more trouble (aggregating) until they have had a chance to refold to their normal, functional form.
"The general strategy for cells is to prevent aggregation from happening in the first place," says Lindquist, Howard Hughes Investigator and professor in the Department of Molcular Genetics and Cell Biology.
"We thought that Hsps bind to sticky surfaces presented by denatured proteins to
prevent them from interacting and forming a blob, and they do. But now we have
shown that at least one heat shock protein, namely Hsp104, has the ability to
rescue proteins that have already a
Contact: Sharon Parmet
University of Chicago Medical Center