Protein Folding in Archaea

The correct three-dimensional structure of a protein is essential for its biological function. In vivo protein folding relies on assistance of so-called chaperones to guarantee a rapid and reliable adoption of the native state. The barrel shapedchaperonins are a particular class of chaperones, they are absolutely essential and present in virtually every living cell. Chaperonins are divided into two distinct groups: the group I chaperonins in Bacteria (i.e. GroEL in E. coli) and group II chaperonins in Archaea and Eukaryotes.This study provides the first complete substrate spectrum of a group II chaperonin, the thermosome of the mesophilic archaeon Methanosarcina mazei. In addition, the unique coexistence of both chaperonin groups in M. mazei allowed direct comparison of the substrate spectra of a bacterial and a eukaryo-typic folding machine.Substrate selection clearly differs among both chaperonin groups and is driven by a combination of physical properties, structural features and less defined characteristics such as the evolutionary status and the phylogenetic origin of the substrate protein.