Steroid-hormone-receptor maturation is a multi-step process that involves several TPR (tetratricopeptide repeat) proteins that bind to the maturation complex via the C-termini of hsp70 (heat-shock protein 70) and hsp90 (heat-shock protein 90). We produced a random T7 peptide library to investigate the roles played by the C-termini of the two heat-shock proteins in the TPR–hsp interactions. Surprisingly, phages with the MEEVD sequence, found at the C-terminus of hsp90, were not recovered from our biopanning experiments. However, two groups of phages were isolated that bound relatively tightly to HsPP5 (Homo sapiens protein phosphatase 5) TPR. Multiple copies of phages with a C-terminal sequence of LFG were isolated. These phages bound specifically to the TPR domain of HsPP5, although mutation studies produced no evidence that they bound to the domain's hsp90-binding groove. However, the most abundant family obtained in the initial screen had an aspartate residue at the C-terminus. Two members of this family with a C-terminal sequence of VD appeared to bind with approximately the same affinity as the hsp90 C-12 control. A second generation pseudo-random phage library produced a large number of phages with an LD C-terminus. These sequences acted as hsp70 analogues and had relatively low affinities for hsp90-specific TPR domains. Unfortunately, we failed to identify residues near hsp90's C-terminus that impart binding specificity to individual hsp90–TPR interactions. The results suggest that the C-terminal sequences of hsp70 and hsp90 act primarily as non-specific anchors for TPR proteins.
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Research Article|
October 12 2009
C-terminal sequences of hsp70 and hsp90 as non-specific anchors for tetratricopeptide repeat (TPR) proteins
Andrew J. Ramsey;
2To whom correspondence should be addressed (email [email protected]).
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Lance C. Russell;
Lance C. Russell
1Department of Pharmacology, University of South Alabama, Mobile, AL 36688, U.S.A.
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Michael Chinkers
Michael Chinkers
1Department of Pharmacology, University of South Alabama, Mobile, AL 36688, U.S.A.
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Publisher: Portland Press Ltd
Received:
April 06 2009
Revision Received:
August 14 2009
Accepted:
August 18 2009
Accepted Manuscript online:
August 18 2009
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© The Authors Journal compilation © 2009 Biochemical Society
2009
Biochem J (2009) 423 (3): 411–419.
Article history
Received:
April 06 2009
Revision Received:
August 14 2009
Accepted:
August 18 2009
Accepted Manuscript online:
August 18 2009
Citation
Andrew J. Ramsey, Lance C. Russell, Michael Chinkers; C-terminal sequences of hsp70 and hsp90 as non-specific anchors for tetratricopeptide repeat (TPR) proteins. Biochem J 1 November 2009; 423 (3): 411–419. doi: https://doi.org/10.1042/BJ20090543
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