The structure of FKBP38 in complex with the MEEVD tetratricopeptide binding-motif of Hsp90

Abstract

Tetratricopeptide (TPR) domains are known protein interaction domains. We show that the TPR domain of FKBP8 selectively binds Hsp90, and interactions upstream of the conserved MEEVD motif are critical for tight binding. In contrast FKBP8 failed to bind intact Hsp70. The PPIase domain was not essential for the interaction with Hsp90 and binding was completely encompassed by the TPR domain alone. The conformation adopted by Hsp90 peptides, containing the conserved MEEVD motif, in the crystal structure were similar to that seen for the TPR domains of CHIP, AIP and Tah1. The carboxylate clamp interactions with bound Hsp90 peptide were a critical component of the interaction and mutation of Lys 307, involved in the carboxylate clamp, completely disrupted the interaction with Hsp90. FKBP8 binding to Hsp90 did not substantially influence its ATPase activity.

Combined x-ray crystallography and computational modeling approach to investigate the Hsp90 C-terminal peptide binding to FKBP51

“…Most commonly the value of dissociation constant calculated using this method is slightly higher than the one observed using isothermal titration calorimetry or surface plasmon resonance because of the fact that the dissociation constant is positively correlated to the temperature of the system 35 . However, the dissociation constant value for the complex is very similar to the reported dissociation constant of FKBP38-MEEVD peptide 30 .…”

“…Intriguingly, the structure of the complex was similar to other complexes of MEEVD peptides with TPR domains such as FKBP38-MEEVD peptide complex 30 indicating the importance and conservation of di-carboxylate clamp as an essential part of the complex formation. Unfortunately, we could not see any differential binding pattern between Hsp90 and Hsp70 C-terminal peptide binding to the TPR domains.…”

“…When calculating the electron density using the deposited coordinates (1QZ2) and the structure factors, we could not generate the convincing electron density maps for the peptide in the FKBP52-peptide complex. We believe that the peptide structure in the complex is not modeled correctly as observed earlier 30 . Our own peptide electron density maps are reasonable as presented in Fig.…”

“…Unfortunately, we could not see any differential binding pattern between Hsp90 and Hsp70 C-terminal peptide binding to the TPR domains. Since the structure of FKBP52-Hsp90 MEEVD peptide complex is not correct as discussed in a latest publication 30 , we were not able to conclude the differences between binding of Hsp90 C-terminal peptide to FKBP51 and FKBP52. The conservation profile of TPR domains of several di-carboxylate clamp TPR containing proteins indicated that the important amino acid residues which take part in hydrogen bonding and salt bridge formation such as Lys329, Glu273, Asn322, Lys272 and Lys352 are highly conserved as evident from the current results and from the reported literature as well.…”

“…Use of computational drug design tools in early phase drug discovery has grown rapidly owing to their high speed and low cost 27 , 28 . Structure based drug design (SBDD) can be employed as a tool to identify small molecule inhibitors of this interaction taking the advantage of the availability of the 3D crystal structures of FKBP52 29 , FKBP38 30 , FKBP37/AIP 31 and Cyp40 32 in complex with the EEVD peptides. These crystal structures reveal that the TPR domain binds to the Hsp70/Hsp90 C-terminal peptide in more or less similar fashion which makes the task of identifying selective inhibitors of a specific co-chaperone very challenging.…”