Hsp60

The class of 60 - kDa heat shock proteins, also referred to as chaperonins, are one of the most important components of the chaperone in the cells of bacteria and eukaryotes. Chaperonins help newly synthesized proteins in the folding of their physiological secondary structure. In eukaryotes, Hsp60 proteins are exclusively located in the mitochondria. Vertebrates such as humans have only the HSPD1 gene encoding a Hsp60. Mutations in this gene are responsible for hereditary forms of spastic paraplegia and leukodystrophy.

Classification

Hsp60 proteins are divided into two classes:

• Class 1 consists of Hsp60 in mitochondria and GroEL in bacteria, proteins that form seven -membered ring " barrels ", the "cover" and " bottom " of each 7 molecules consist Hsp10 or GroES.
• Class 2 consists of the cytosolic chaperonin CCT ( also c- cpn or TRiC ) in higher eukaryotes and archaea in the thermosome. These proteins form 8 - to 9 - membered rings. Here are "cover" and " bottom" of the " barrels " formed by outgrowths of the tertiary structure of the proteins themselves.

Function

GroEL is required for the synthesis of an estimated one third of all medium-sized (30-60 kDa) bacterial proteins. Unfolded amino acid chains bind nonspecifically to this GroEL ( ie many different proteins can bind as a substrate to GroEL ), are included, and may take their physiological structure inside the Chaperoninkomplexes. After a cycle of ATP hydrolysis to 7 GroEL subunits, the folded substrate protein is released.

CCT has a much more limited range of substrates. Here unfolded proteins bind specifically to one or more of the CCT subunits. Among the proteins that the CCT need as chaperones, cytoskeletal proteins actin and tubulin, some proteins similar to actin, and apparently are only a few others.