Hsp104: Proteins and Enzymes

Heat Shock Proteins (HSP) are expressed in response to various biological stresses, including high temperatures. There are several major families of HSPs including HSP 70, HSP 90 and HSP 100. The HSP 100 proteins generally have amino acid sequences of about 900 residues and contain two nucleotide-binding sites. Within the HSP 100 family of proteins, yeast express an ~104 kDa form which is necessary to protect cells from various stress conditions such as heat, heavy metals and ethanol, though mutation studies have shown that the protein is not required for normal growth. Yeast HSP 104 has been shown to be a ClpB protein with significant sequence homology to E. coli ClpB, particularly in the two nucleotide-binding sites.