Figure 4.

Hsp90 chaperones functional domains and conformations. Section A depicts the functional domains as individually crystallized, superimposed unto one arm of an open dimeric structure (PDBID: 2IOQ). The nucleotide binding domain (PDBID: 1AH8), the middle domain (PDBID: 1HK7), and the C-terminal domain (PDBID: 1SF8) are colored red, green, and yellow, respectively. Section B shows the nucleotide dependent transitions from an ADP-bound open form to an ATP-bound closed form. The structure of the open form was made by fitting an ADP-bound monomer structure (PDBID: 2IOQ) unto the ATP-bound dimer structure (PDBID: 2IOP), using the last two helices as bases. The monomeric arms of Hsp90 are colored yellow and blue. An overlaid structure of the open and closed conformations shows the expected movement of the arms. The structures of the open conformation are colored gray for this image.