Classification
The principal heat-shock proteins that have chaperone activity belong to five conserved classes: HSP33, HSP60, HSP70, HSP90, HSP100, and the small heat-shock proteins (sHSPs).
| Approximate molecular weight
(kDa) |
Prokaryotic proteins | Eukaryotic proteins | Function |
|---|---|---|---|
| 10 kDa | GroES | Hsp10 | |
| 20-30 kDa | GrpE | The HspB group of Hsp. Eleven members in mammals including Hsp27, HSPB6 or HspB1 | |
| 40 kDa | DnaJ | Hsp40 | Co-factor of Hsp70 |
| 60 kDa | GroEL, 60kDa antigen | Hsp60 | Involved in protein folding after its post-translational import to the mitochondrion/chloroplast |
| 70 kDa | DnaK | The HspA group of Hsp including Hsp71, Hsp70, Hsp72, Grp78 (BiP), Hsx70 found only in primates | Protein folding and unfolding, provides thermotolerance to cell on exposure to heat stress. Also prevents protein folding during post-translational import into the mitochondria/chloroplast. |
| 90 kDa | HtpG, C62.5 | The HspC group of Hsp including Hsp90, Grp94 | Maintenance of steroid receptors and transcription factors |
| 100 kDa | ClpB, ClpA, ClpX | Hsp104, Hsp110 | Tolerance of extreme temperature |
Although the most important members of each family are tabulated here, it should be noted that some species may express additional chaperones, co-chaperones, and heat shock proteins not listed. In addition, many of these proteins may have multiple splice variants (Hsp90α and Hsp90β, for instance) or conflicts of nomenclature (Hsp72 is sometimes called Hsp70).
Read more about this topic: Heat Shock Protein