Heat Shock Protein - Classification

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).

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