The multitalented type III chaperones: all you can do with 15 kDa

Despite the fact that type III chaperones were discovered approximately 10 years ago, the precise role of most of them is still mysterious. A panoply of functions has been proposed for the members of this family of proteins. Type III chaperones have been suggested to act as anti-aggregation and stabilizing factors. They have also been proposed to keep their substrates in unfolded or partially folded structures, set a hierarchy on secretion, and participate in the regulation of the transcription of the type III substrates. Here, we review this enigmatic family of proteins, and discuss the experimental data supporting the roles proposed for type III chaperones.