Specialized chaperones

According to Véronique Albanèse, Judith Frydman, and colleagues (Stanford University, Stanford, CA), yeast evolved two distinct chaperone networks—one to fold newly synthesized proteins, and another to deal with stress-induced misfolding. The dedication is a departure from the prokaryotic chaperone system.

Bacteria have only one ribosome-bound chaperone and use primarily the same two chaperones to fold proteins after translation and then again after stress. But bioinformatic analyses by the authors suggested that yeast are different; whereas stresses such as heat and oxidation induced one set of cytosolic chaperones, they repressed another. The proteins from the repressed set were associated with ribosomes, and mutant lines lacking in this set were hypersensitive to translation inhibitors.

The authors propose that eukaryotes have a set of chaperones dedicated to nascent polypeptide folding during translation. This...