Hsp20 (Saci_0922, Q4JA95) - Research Notes

Overview

Hsp20 is a small heat shock protein (sHSP) of the alpha-crystallin/Hsp20 family from the thermoacidophilic crenarchaeon Sulfolobus acidocaldarius. It is 173 amino acids (19.9 kDa). Together with Hsp14 and Hsp60 (group II chaperonin/thermosome), Hsp20 constitutes the core chaperone machinery of S. acidocaldarius, which lacks Hsp70, Hsp90, and Hsp100.

Key Publications

PMID:30293966 - Roy et al. (2018) Biochim Biophys Acta Biomembr

"The oligomeric plasticity of Hsp20 of Sulfolobus acidocaldarius protects environment-induced protein aggregation and membrane destabilization"

Key findings:
- ~24-mer at room temperature (25 degrees C); higher oligomeric forms at higher temperature (50-70 degrees C) and lower pH (3.0-5.0) PMID:30293966
- Dimer is the functional conformation in the presence of aggregating substrate proteins PMID:30293966
- Hydrophobic microenvironment regulates oligomeric plasticity PMID:30293966
- Protects against stress-induced protein aggregation PMID:30293966
- Interacts with membrane lipids via hydrophobic interaction PMID:30293966
- Lowers the propensity of in vitro phase transition of bacterial and archaeal lipids PMID:30293966
- Found in secretory vesicles PMID:30293966

PMID:34637594 - Roy et al. (2022) FEBS J

"Archaeal Hsp14 drives substrate shuttling between small heat shock proteins and thermosome"

Key findings relevant to Hsp20:
- Hsp20 forms hetero-oligomers with Hsp14 at 50-70 degrees C PMID:34637594
- Hsp20-captured substrates can be transferred via Hsp14 to the thermosome PMID:34637594

PMID:37516156 - Bhowmick et al. (2023) Res Microbiol

"Heat shock response in Sulfolobus acidocaldarius and first implications for cross-stress adaptation"

Key findings:
- hsp20 plays crucial roles in the majority of stress conditions (heat, oxidative, nutrient) PMID:37516156
- Highest increase in abundance after 60 min of heat shock treatment (from Frontiers review)

PMID:32562000 - Baes et al. (2020) Extremophiles

"Defining heat shock response for the thermoacidophilic model crenarchaeon Sulfolobus acidocaldarius"

Molecular Functions

  1. Unfolded protein binding (GO:0051082) - Binds unfolded/aggregating substrate proteins; dimer is the active form PMID:30293966
  2. Lipid binding (GO:0008289) - Interacts with membrane lipids via hydrophobic interaction, stabilizes membranes PMID:30293966

Biological Processes

  1. Response to heat (GO:0009408) - Upregulated under heat shock and other stresses [PMID:32562000, PMID:37516156]
  2. Protein folding (GO:0006457) - Participates in the sHSP pathway preventing aggregation [PMID:30293966, PMID:34637594]
  3. Negative regulation of protein aggregation - Prevents stress-induced protein aggregation PMID:30293966
  4. Membrane stabilization - Lowers propensity of lipid phase transition, stabilizes membranes under stress PMID:30293966

Cellular Component

  1. Cytoplasm (GO:0005737) - sHSPs are cytoplasmic proteins
  2. Extracellular vesicle - Found in secretory vesicles PMID:30293966

Domain Architecture