Hsp14 (Saci_1665) is a 126-amino acid (14.3 kDa) small heat shock protein (sHSP) of the alpha-crystallin/Hsp20 family from the thermoacidophilic crenarchaeon Sulfolobus acidocaldarius. In this organism, which lacks Hsp70, Hsp90, and Hsp100, Hsp14 fills a critical gap in the chaperone pathway by acting as a substrate shuttle between the holdase sHSPs and the group II chaperonin (thermosome/Hsp60). The Hsp14 dimer is the active form that binds aggregation-prone substrates and forms hetero-oligomers with Hsp20 at elevated temperatures (50-70 degrees C). Hsp14 then directly interacts with Hsp60 via an enthalpy-driven mechanism to transfer captured substrates for ATP-dependent refolding, functionally replacing the Hsp70 system found in most other organisms.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0140309 unfolded protein holdase activity | IDA PMID:34637594 Archaeal Hsp14 drives substrate shuttling between small heat... | NEW | Summary: Hsp14 shuttles sHSP-captured unfolded substrates to the thermosome (Hsp60) for ATP-dependent refolding, filling the role of the absent Hsp70. Direct physical interaction between Hsp14 and Hsp60 was demonstrated by ITC (enthalpy-driven). Reason: Hsp14 transfers aggregation-prone substrates from sHSPs to Hsp60 for refolding, which is the defining activity of GO:0140309 (unfolded protein holdase activity, defined as escorting an unfolded client to an acceptor). This is the most distinctive function of Hsp14. Supporting Evidence: PMID:34637594 Hsp14 could transfer sHsp-captured substrate proteins to Hsp60, which then refolds them back to their active form PMID:34637594 an enthalpy-driven direct physical interaction between Hsp14 and Hsp60 |
| GO:0006457 protein folding | IDA PMID:34637594 Archaeal Hsp14 drives substrate shuttling between small heat... | NEW | Summary: Hsp14 participates in protein folding by capturing unfolded substrates and transferring them to the thermosome (Hsp60) for ATP-dependent refolding. Reason: Hsp14 is directly involved in the protein folding pathway by delivering substrates to the thermosome refolding machinery. Supporting Evidence: PMID:34637594 Hsp14 could transfer sHsp-captured substrate proteins to Hsp60, which then refolds them back to their active form |
| GO:0034605 cellular response to heat | IDA PMID:37516156 Heat shock response in Sulfolobus acidocaldarius and first i... | NEW | Summary: Hsp14 is upregulated under heat shock and plays a crucial role in the heat stress response of S. acidocaldarius. Reason: Transcriptomic and qRT-PCR analyses demonstrated upregulation of hsp14 under heat shock (92 degrees C) and other stresses. Supporting Evidence: PMID:37516156 The results demonstrated that the gene thΞ² encoding the Ξ² subunit of the thermosome, as well as hsp14 and hsp20, play crucial roles in the majority of stress conditions PMID:32562000 a dynamic increase in mRNA levels of all relevant heat shock proteins |
| GO:0005737 cytoplasm | IDA PMID:34637594 Archaeal Hsp14 drives substrate shuttling between small heat... | NEW | Summary: Hsp14 is a cytoplasmic sHSP that interacts with other cytoplasmic chaperones (Hsp20 and Hsp60/thermosome). Reason: sHSPs are cytoplasmic proteins; Hsp14 was purified from and characterized in the cytoplasmic fraction. Supporting Evidence: PMID:34637594 the dimer is the active form of Hsp14, and it forms an oligomeric storage form at a higher temperature |
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Q: What is the stoichiometry and structure of the Hsp14-Hsp60 interaction?
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