title: Specific Binding of Tetratricopeptide Repeat Proteins to Heat Shock Protein 70 (Hsp70) and Heat Shock Protein 90 (Hsp90) Is Regulated by Affinity and Phosphorylation.
abstract: Heat shock protein 70 (Hsp70) and heat shock protein 90 (Hsp90) require the help of tetratricopeptide repeat (TPR) domain-containing cochaperones for many of their functions. Each monomer of Hsp70 or Hsp90 can interact with only a single TPR cochaperone at a time, and each member of the TPR cochaperone family brings distinct functions to the complex. Thus, competition for TPR binding sites on Hsp70 and Hsp90 appears to shape chaperone activity. Recent structural and biophysical efforts have improved our understanding of chaperone-TPR contacts, focusing on the C-terminal EEVD motif that is present in both chaperones. To better understand these important protein-protein interactions on a wider scale, we measured the affinity of five TPR cochaperones, CHIP, Hop, DnaJC7, FKBP51, and FKBP52, for the C-termini of four members of the chaperone family, Hsc70, Hsp72, Hsp90α, and Hsp90β, in vitro. These studies identified some surprising selectivity among the chaperone-TPR pairs, including the selective binding of FKBP51/52 to Hsp90α/β. These results also revealed that other TPR cochaperones are only able to weakly discriminate between the chaperones or between their paralogs. We also explored whether mimicking phosphorylation of serine and threonine residues near the EEVD motif might impact affinity and found that pseudophosphorylation had selective effects on binding to CHIP but not other cochaperones. Together, these findings suggest that both intrinsic affinity and post-translational modifications tune the interactions between the Hsp70 and Hsp90 proteins and the TPR cochaperones.
authors.affiliation: Program in Chemical Biology, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors.forename: Victoria A
authors.initials: VA
authors.lastname: Assimon
authors.affiliation: Program in Chemical Biology, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Southworth
authors.affiliation: Department of Pharmaceutical Chemistry, University of California at San Francisco , San Francisco, California 94158, United States.
authors.forename: Jason E
authors.initials: JE
authors.lastname: Gestwicki
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D018841:HSP90 Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D010766:Phosphorylation; D011485:Protein Binding; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D060066:Protein Interaction Maps; D022021:Tacrolimus Binding Proteins / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D000099159:Tacrolimus Binding Protein 5
chemical_list: D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D018398:Homeodomain Proteins; D022021:Tacrolimus Binding Proteins; D025521:Tumor Suppressor Proteins; D044767:Ubiquitin-Protein Ligases; D000099159:Tacrolimus Binding Protein 5; C476884:HOPX protein, human; C467728:STUB1 protein, human; C403485:tacrolimus binding protein 4