Structure of the CHIP:UbcH5a complex. A. Asymmetric unit of the crystallized zebrafish CHIP U-box: UbcH5a complex, showing the U-box dimer (blue) with two bound UbcH5a molecules (yellow). Secondary structure elements that mediate the interaction between the U-boxes and UbcH5a are labelled in blue or black for the U-boxes and UbcH5a respectively. Active site cysteines of the UbcH5a molecules are shown in ball-and-stick representation and labelled. B. Model of the CHIP:UbcH5a complex, CHIP, built by superimposing the U-box dimer and one UbcH5a molecule from the structure shown in panel A onto the crystal structure of murine CHIP, PDB:2C2L . The TPR and helical domains of the two CHIP monomers are coloured light and dark grey. One TPR domain is behind the rest of the molecule and is left unlabelled for clarity.