Hop: more than an Hsp70/Hsp90 adaptor protein

Bioessays. 2004 Oct;26(10):1058-68. doi: 10.1002/bies.20107.


Molecular chaperones facilitate the correct folding of other proteins under physiological and stress conditions. Recently it has become evident that various co-chaperone proteins regulate the cellular functions of these chaperones, particularly Hsp70 and Hsp90. Hop is one of the most extensively studied co-chaperones that is able to directly associate with both Hsp70 and Hsp90. The current dogma proposes that Hop functions primarily as an adaptor that directs Hsp90 to Hsp70-client protein complexes in the cytoplasm. However, recent evidence suggests that Hop can also modulate the chaperone activities of these Hsps, and that it is not dedicated to Hsp70 and Hsp90. While the co-chaperone function of Hop within the cytoplasm has been extensively studied, its association with nuclear complexes and prion proteins remains to be elucidated. This article will review the structural features of Hop, and the evidence that its biological function is considerably broader than previously envisaged.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Amino Acid Sequence
  • Animals
  • HSP70 Heat-Shock Proteins / physiology
  • HSP90 Heat-Shock Proteins / physiology
  • Heat-Shock Proteins / chemistry
  • Heat-Shock Proteins / genetics*
  • Heat-Shock Proteins / physiology*
  • Humans
  • Models, Molecular
  • Molecular Chaperones / chemistry
  • Molecular Chaperones / genetics*
  • Molecular Chaperones / physiology*
  • Molecular Sequence Data
  • Protein Structure, Tertiary
  • Sequence Homology, Amino Acid
  • Subcellular Fractions / metabolism


  • HSP70 Heat-Shock Proteins
  • HSP90 Heat-Shock Proteins
  • Heat-Shock Proteins
  • Molecular Chaperones
  • STIP1 protein, human