The importance of protein folding
Joachim Pietzsch

Figure 4 | Chaperones and protein folding
Part (a) shows the basic mechanism of the Escherichia coli Hsp70 system (which comprises DnaK (Hsp70), DnaJ (Hsp40), and GrpE). DnaJ presents an unfolded protein (U) DnaK, which holds onto it until folding to the native state (N) can occur, provided that all structural elements necessary for folding are available. Part (b) shows how the E. coli chaperonin system (GroEL–GroES; shown in cross section) contains an unfolded protein in an enclosed cage to allow it to fold. When the protein has folded into the native state, it is then released.
Modified with permission from Teter, S. & Hartl, F. U. Protein folding in vivo. in Encyclopedia of Life Sciences (Nature Publishing Group, London, 2001) © Macmillian Magazines Ltd.