Figure 5

Schematic representation of the "anchoring and docking" mechanism by which Hsp40 (green) delivers a non-native peptide (blue) to Hsp70 (yellow). The cartoon drawing depicts an Hsp70 molecule that is divided into its ATPase domain, peptide-binding groove and the lid domain. The J-domain and peptide-binding fragment of Hsp40 are shown schematically. The C-terminus "anchor" region of Hsp70 is shown in a red arrow. The blue line denotes the extended non-native polypeptide. The thick black region in the non-native polypeptide indicates the hydrophobic region that can be recognized by Hsp40 peptide-binding fragment and Hsp70 peptide-binding domain. a) When Hsp40 is free of the non-native polypeptide, the cleft between the two monomers is narrow. b) The cleft is widened up when Hsp40 binds the non-native polypeptide. This may help to stretch the polypeptides into the extended conformations. c) The cleft within Hsp40 is further opened up when the Hsp70 C-terminus interacts with the Hsp40. d) When the Hsp70-non-native polypeptide complex is released from Hsp40, the cleft within Hsp40 returns to the narrow state.