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Chaperone ligand-discrimination by the TPR-domain protein Tah1.

Millson SH, Vaughan CK, Zhai C, Ali MM, Panaretou B, Piper PW, Pearl LH, Prodromou C - Biochem. J. (2008)

Bottom Line: Tah1 [TPR (tetratricopeptide repeat)-containing protein associated with Hsp (heat-shock protein) 90] has been identified as a TPR-domain protein.Amino-acid-sequence alignments suggest that Tah1 is most similar to the TPR2b domain of Hop (Hsp-organizing protein) which when mutated reduces binding to both Hsp90 and Hsp70.In the present study we also show that Tah1 can affect the ATPase activity of Hsp90, in common with some other TPR-domain proteins.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.

ABSTRACT
Tah1 [TPR (tetratricopeptide repeat)-containing protein associated with Hsp (heat-shock protein) 90] has been identified as a TPR-domain protein. TPR-domain proteins are involved in protein-protein interactions and a number have been characterized that interact either with Hsp70 or Hsp90, but a few can bind both chaperones. Independent studies suggest that Tah1 interacts with Hsp90, but whether it can also interact with Hsp70/Ssa1 has not been investigated. Amino-acid-sequence alignments suggest that Tah1 is most similar to the TPR2b domain of Hop (Hsp-organizing protein) which when mutated reduces binding to both Hsp90 and Hsp70. Our alignments suggest that there are three TPR-domain motifs in Tah1, which is consistent with the architecture of the TPR2b domain. In the present study we find that Tah1 is specific for Hsp90, and is able to bind tightly the yeast Hsp90, and the human Hsp90alpha and Hsp90beta proteins, but not the yeast Hsp70 Ssa1 isoform. Tah1 acheives ligand discrimination by favourably binding the methionine residue in the conserved MEEVD motif (Hsp90) and positively discriminating against the first valine residue in the VEEVD motif (Ssa1). In the present study we also show that Tah1 can affect the ATPase activity of Hsp90, in common with some other TPR-domain proteins.

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Pymol diagram showing the interaction of the MEEVD peptide with the TPR2a domain of HopResidues are labelled and those residues in brackets are the equivalent residues of Tah1. The single letter amino acid code is used for the MEEVD peptide sequence. Water molecules are shown as cyan coloured balls and polar interactions are shown as broken lines.
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Figure 2: Pymol diagram showing the interaction of the MEEVD peptide with the TPR2a domain of HopResidues are labelled and those residues in brackets are the equivalent residues of Tah1. The single letter amino acid code is used for the MEEVD peptide sequence. Water molecules are shown as cyan coloured balls and polar interactions are shown as broken lines.

Mentions: In the TPR1–VEEVD and TPR2a–MEEVD complexes most of the direct hydrogen-bonded interactions with bound peptide involve the main chain and are therefore sequence independent. Both complexes have a highly conserved two-carboxylate clamp. In the TPR2a complex the terminal main chain carboxylate of MEEVD is hydrogen bonded to Lys229, Asn233 and Asn264. These residues are also conserved in Tah1 (Lys8, Asn12 and Asn43 respectively; see Supplementary Figure S1 and Figure 2). However, in contrast, residues that interact with the side chain of the terminal aspartate residue, which is bound by Lys301 and Gln298 in TPR2a, are not conserved in Tah1 (Thr70 and His73 respectively). Consequently, if a two-carboxylate clamp exists in the peptide-bound Tah1 complex it is clearly different to that seen in TPR2a. Other electrostatic interactions include a tetrahedrally co-ordinated water molecule that interacts with the carboxylate side chain of the terminal aspartate residue, and with the main chain carbonyl of Thr263 (Ser42 in Tah1), the guanidinium group of Arg305 (Arg77 in Tah1) and the side chain carbonyl of Asn264 (Asn43 in Tah1). The side chain amide of Asn264 is also involved in main chain interactions with the backbone amide of the terminal aspartate residue, whereas the guanidinium group of Arg305 also contacts the main chain carbonyl and amide (via a water molecule) of Glu−2 (S−6RMEEVD0). Furthermore, the hydroxy group of Tyr236 (Phe15 in Tah1; Supplementary Figure S1 and Figure 2) contacts the main chain carbonyl of Glu−3, an interaction not possible with Phe15 of Tah1, whereas the side chain carbonyl group of Glu271 (Lys50 in Tah1) contacts the main chain amide of Glu−3. The only interactions to side chains (excluding the two carboxylate clamp) are between the guanidinium group of Arg305 and the side chain amide of Asn308 (Lys79 in Tah1) to the carboxylate group of Glu−3. Additionally, Val−1 is involved in a hydrophobic interaction with a pocket formed by Asn233, Tyr236 (Phe15 in Tah1), Asn264 and Ala267 (Met46 in Tah1), whereas the side chain of Met−4 binds between Tyr236 (Phe15 in Tah1) and Glu271 (Lys50 in Tah1). Two further van der Waals contacts involve the side chain of Glu−3 and Asp−0 with Phe270 (Ile49 in Tah1) and Thr260 (Val39 in Tah1) respectively. It should be noted that the Glu−2 side chain is not involved in interactions. In summary, our alignments suggest that there are significant residue differences between the TPR2a and the Tah1 TPR domain that point to differences in the precise way that they would bind the MEEVD peptide (Supplementary Figure S1 and Figure 2).


Chaperone ligand-discrimination by the TPR-domain protein Tah1.

Millson SH, Vaughan CK, Zhai C, Ali MM, Panaretou B, Piper PW, Pearl LH, Prodromou C - Biochem. J. (2008)

Pymol diagram showing the interaction of the MEEVD peptide with the TPR2a domain of HopResidues are labelled and those residues in brackets are the equivalent residues of Tah1. The single letter amino acid code is used for the MEEVD peptide sequence. Water molecules are shown as cyan coloured balls and polar interactions are shown as broken lines.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2865030&req=5

Figure 2: Pymol diagram showing the interaction of the MEEVD peptide with the TPR2a domain of HopResidues are labelled and those residues in brackets are the equivalent residues of Tah1. The single letter amino acid code is used for the MEEVD peptide sequence. Water molecules are shown as cyan coloured balls and polar interactions are shown as broken lines.
Mentions: In the TPR1–VEEVD and TPR2a–MEEVD complexes most of the direct hydrogen-bonded interactions with bound peptide involve the main chain and are therefore sequence independent. Both complexes have a highly conserved two-carboxylate clamp. In the TPR2a complex the terminal main chain carboxylate of MEEVD is hydrogen bonded to Lys229, Asn233 and Asn264. These residues are also conserved in Tah1 (Lys8, Asn12 and Asn43 respectively; see Supplementary Figure S1 and Figure 2). However, in contrast, residues that interact with the side chain of the terminal aspartate residue, which is bound by Lys301 and Gln298 in TPR2a, are not conserved in Tah1 (Thr70 and His73 respectively). Consequently, if a two-carboxylate clamp exists in the peptide-bound Tah1 complex it is clearly different to that seen in TPR2a. Other electrostatic interactions include a tetrahedrally co-ordinated water molecule that interacts with the carboxylate side chain of the terminal aspartate residue, and with the main chain carbonyl of Thr263 (Ser42 in Tah1), the guanidinium group of Arg305 (Arg77 in Tah1) and the side chain carbonyl of Asn264 (Asn43 in Tah1). The side chain amide of Asn264 is also involved in main chain interactions with the backbone amide of the terminal aspartate residue, whereas the guanidinium group of Arg305 also contacts the main chain carbonyl and amide (via a water molecule) of Glu−2 (S−6RMEEVD0). Furthermore, the hydroxy group of Tyr236 (Phe15 in Tah1; Supplementary Figure S1 and Figure 2) contacts the main chain carbonyl of Glu−3, an interaction not possible with Phe15 of Tah1, whereas the side chain carbonyl group of Glu271 (Lys50 in Tah1) contacts the main chain amide of Glu−3. The only interactions to side chains (excluding the two carboxylate clamp) are between the guanidinium group of Arg305 and the side chain amide of Asn308 (Lys79 in Tah1) to the carboxylate group of Glu−3. Additionally, Val−1 is involved in a hydrophobic interaction with a pocket formed by Asn233, Tyr236 (Phe15 in Tah1), Asn264 and Ala267 (Met46 in Tah1), whereas the side chain of Met−4 binds between Tyr236 (Phe15 in Tah1) and Glu271 (Lys50 in Tah1). Two further van der Waals contacts involve the side chain of Glu−3 and Asp−0 with Phe270 (Ile49 in Tah1) and Thr260 (Val39 in Tah1) respectively. It should be noted that the Glu−2 side chain is not involved in interactions. In summary, our alignments suggest that there are significant residue differences between the TPR2a and the Tah1 TPR domain that point to differences in the precise way that they would bind the MEEVD peptide (Supplementary Figure S1 and Figure 2).

Bottom Line: Tah1 [TPR (tetratricopeptide repeat)-containing protein associated with Hsp (heat-shock protein) 90] has been identified as a TPR-domain protein.Amino-acid-sequence alignments suggest that Tah1 is most similar to the TPR2b domain of Hop (Hsp-organizing protein) which when mutated reduces binding to both Hsp90 and Hsp70.In the present study we also show that Tah1 can affect the ATPase activity of Hsp90, in common with some other TPR-domain proteins.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.

ABSTRACT
Tah1 [TPR (tetratricopeptide repeat)-containing protein associated with Hsp (heat-shock protein) 90] has been identified as a TPR-domain protein. TPR-domain proteins are involved in protein-protein interactions and a number have been characterized that interact either with Hsp70 or Hsp90, but a few can bind both chaperones. Independent studies suggest that Tah1 interacts with Hsp90, but whether it can also interact with Hsp70/Ssa1 has not been investigated. Amino-acid-sequence alignments suggest that Tah1 is most similar to the TPR2b domain of Hop (Hsp-organizing protein) which when mutated reduces binding to both Hsp90 and Hsp70. Our alignments suggest that there are three TPR-domain motifs in Tah1, which is consistent with the architecture of the TPR2b domain. In the present study we find that Tah1 is specific for Hsp90, and is able to bind tightly the yeast Hsp90, and the human Hsp90alpha and Hsp90beta proteins, but not the yeast Hsp70 Ssa1 isoform. Tah1 acheives ligand discrimination by favourably binding the methionine residue in the conserved MEEVD motif (Hsp90) and positively discriminating against the first valine residue in the VEEVD motif (Ssa1). In the present study we also show that Tah1 can affect the ATPase activity of Hsp90, in common with some other TPR-domain proteins.

Show MeSH