Binding sites for Hsp70 molecular chaperones in natural proteins

M. J. Gething, S. Blond-Elguindi, J. Buchner, A. Fourie, G. Knarr, S. Modrow, L. Nanu, M. Segal, J. Sambrook

Research output: Contribution to journalArticlepeer-review

35 Scopus citations

Abstract

We have analyzed the locations of binding sites for Hsp70 molecular chaperones in several natural proteins, in a process greatly aided by a computer program designed to predict likely binding sites for the ER-located family member, BiP. Identification of Hsp70-binding sites in immunoglobulin molecules, in influenza virus HA glycoprotein, and in the tumor suppressor protein p53 has provided insights into the roles played by the chaperones in protein folding and function. Thus, in the immunoglobulin molecules we studied, BiP-binding sites seem to be preferentially located in the sequences destined to form the interfaces between the heavy- and light-chain subunits, where binding could function to protect the hydrophobic surfaces from off- pathway aggregation reactions until subunit assembly occurs. In the HA molecule, high-affinity sites with which BiP associates stably until HA trimers assemble correctly are located in the stalk domain, which is most intimately associated in the trimer. One particular site includes the first cysteine residue in the HA sequence (residue 14), which forms a disulfide bond with Cys-465 late in the process of folding of the HA molecule. Binding of BiP at this site may inhibit inappropriate disulfide-bond formation. In the p53 protein, high-affinity sites for Hsc70 in the central DNA-binding domain are cryptic in the correctly folded molecule, but are exposed in mutant proteins that lack tumor suppressor function. Studies with p53 peptides also revealed that BiP, Hsc70, and DnaK have both common and divergent peptide-binding specificities. It has been possible to use the BiP Score program to narrow down the precise location of DnaK-binding sites within longer peptide sequences of known binding capacity derived from bacterial (σ32) and bacteriophage (λcIII) proteins. Predictions of potential binding sites for Hsp70 chaperones other than BiP made using the current form of this program will undoubtedly prove most accurate in identifying the class of sequences (probably those with greatest hydrophobicity) for which the chaperones have similar high affinities. Collection of more peptide-binding data is necessary to allow us to refine the program to reflect more accurately the specific sequence preferences of individual Hsp70 family members.

Original languageEnglish
Pages (from-to)417-428
Number of pages12
JournalCold Spring Harbor Symposia on Quantitative Biology
Volume60
DOIs
StatePublished - 1 Jan 1995
Externally publishedYes

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