Hop (protein)

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Stress-induced phosphoprotein 1
Protein STIP1 PDB 1elr.png
PDB rendering based on 1elr.
Available structures
PDB Ortholog search: PDBe, RCSB
Symbols STIP1 ; HEL-S-94n; HOP; IEF-SSP-3521; P60; STI1; STI1L
External IDs OMIM605063 MGI109130 HomoloGene4965 GeneCards: STIP1 Gene
RNA expression pattern
PBB GE STIP1 213330 s at tn.png
PBB GE STIP1 212009 s at tn.png
More reference expression data
Species Human Mouse
Entrez 10963 20867
Ensembl ENSG00000168439 ENSMUSG00000024966
UniProt P31948 Q60864
RefSeq (mRNA) NM_001282652 NM_016737
RefSeq (protein) NP_001269581 NP_058017
Location (UCSC) Chr 11:
63.95 – 63.97 Mb
Chr 19:
7.02 – 7.04 Mb
PubMed search [1] [2]

Hop, occasionally written HOP, is an abbreviation for Hsp70-Hsp90 Organizing Protein. It functions as a co-chaperone which reversibly links together the protein chaperones Hsp70 and Hsp90.

Hop belongs to the large group of co-chaperones, which regulate and assist the major chaperones (mainly heat shock proteins). It is one of the best studied co-chaperones of the Hsp70/Hsp90-complex. It was first discovered in yeast and homologues were identified in human, mouse, rat, insects, plants, parasites, and virus. The family of these proteins is referred to as STI1 (stress inducible protein) and can be divided into yeast, plant, and animal STI1 (Hop).

Synonym protein names[edit]

  • Hop
  • Hsc70/Hsp90-organizing protein
  • NY-REN-11 antigen
  • P60
  • STI1
  • STI1L
  • STIP1
  • Transformation-sensitive protein IEF-SSP-3521

Gene name and Structure[edit]

The gene for human Hop is located on chromosome 11q13.1 and consists of 14 exons.

STI proteins are characterized by some structural features: All homologues have nine tetratricopeptide repeat (TPR) motifs, that are clustered into domains of three TPRs. The TPR motif is a very common structural feature used by many proteins and provides the ability of directing protein-protein interactions. Crystallographic structural information is available for the N-terminal TPR1 and the central TPR2A domains in complex with Hsp90 resp. Hsp70 ligand peptides.[1]


The main function of Hop is to link Hsp70 and Hsp90 together. But recent investigations indicate that it also modulates the chaperone activities of the linked proteins and possibly interacts with other chaperones and proteins. Apart from its role in the Hsp70/Hsp90 "chaperone machine" it seems to participate in other protein complexes too (for example in the signal transduction complex EcR/USP and in the Hepatitis B virus reverse transcriptase complex, which enables the viral replication). It acts as a receptor for prion proteins too.[2][3] Hop is located in diverse cellular regions and also moves between the cytoplasm and the nucleus.


Hop (protein) has been shown to interact with PRNP[4] and Heat shock protein 90kDa alpha (cytosolic), member A1.[5][6]


  1. ^ Scheufler, C, Brinker, A, Bourenkov, G, Pegoraro, S, Moroder, L et al., Bartunik, Hans, Hartl, F.Ulrich, Moarefi, Ismail (2000). "Structure of TPR Domain–Peptide Complexes". Cell 101 (2): 199–210. doi:10.1016/S0092-8674(00)80830-2. PMID 10786835. 
  2. ^ Martins, VR, Graner, E, Garcia-Abreu, J, de Souza, SJ, Mercadante, AF, Veiga, SS, Zanata, SM, Neto, VM et al. (1997). "Complementary hydropathy identifies a cellular prion protein receptor". Nat Med 3 (12): 1376–1382. doi:10.1038/nm1297-1376. PMID 9396608. 
  3. ^ Zanata, SM, Lopes, MH, Mercadante, AF, Hajj, GN, Chiarini, LB, Nomizo, R, Freitas, AR, Cabral, AL et al. (2002). "Stress-inducible protein 1 is a cell surface ligand for cellular prion that triggers neuroprotection". EMBO J 21 (13): 3307–3316. doi:10.1093/emboj/cdf325. PMC 125391. PMID 12093732. 
  4. ^ Zanata, Silvio M; Lopes Marilene H, Mercadante Adriana F, Hajj Glaucia N M, Chiarini Luciana B, Nomizo Regina, Freitas Adriana R O, Cabral Ana L B, Lee Kil S, Juliano Maria A, de Oliveira Elizabeth, Jachieri Saul G, Burlingame Alma, Huang Lan, Linden Rafael, Brentani Ricardo R, Martins Vilma R (July 2002). "Stress-inducible protein 1 is a cell surface ligand for cellular prion that triggers neuroprotection". EMBO J. (England) 21 (13): 3307–16. doi:10.1093/emboj/cdf325. ISSN 0261-4189. PMC 125391. PMID 12093732. 
  5. ^ Scheufler, C; Brinker A; Bourenkov G; Pegoraro S; Moroder L; Bartunik H; Hartl F U; Moarefi I (April 2000). "Structure of TPR domain-peptide complexes: critical elements in the assembly of the Hsp70-Hsp90 multichaperone machine". Cell (UNITED STATES) 101 (2): 199–210. doi:10.1016/S0092-8674(00)80830-2. ISSN 0092-8674. PMID 10786835. 
  6. ^ Johnson, B D; Schumacher R J; Ross E D; Toft D O (February 1998). "Hop modulates Hsp70/Hsp90 interactions in protein folding". J. Biol. Chem. (UNITED STATES) 273 (6): 3679–86. doi:10.1074/jbc.273.6.3679. ISSN 0021-9258. PMID 9452498. 

Further reading[edit]


This article is mainly based on this review:

Odunuga OO, Longshaw VM,and Blatch GL. BioEssays 26:1058–1068, 2004.