SSZ1/YHR064C Summary Help

Standard Name SSZ1 1
Systematic Name YHR064C
Alias PDR13 2
Feature Type ORF, Verified
Description Hsp70 protein that interacts with Zuo1p (a DnaJ homolog); interacts with Zuo1p to form a ribosome-associated complex that binds the ribosome via the Zuo1p subunit; also involved in pleiotropic drug resistance via sequential activation of PDR1 and PDR5; binds ATP (3, 4, 5 and see Summary Paragraph)
Chromosomal Location
ChrVIII:227141 to 225525 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Gene Ontology Annotations All SSZ1 GO evidence and references
  View Computational GO annotations for SSZ1
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 5 genes
Classical genetics
Large-scale survey
131 total interaction(s) for 94 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 104
  • Affinity Capture-RNA: 1
  • Affinity Capture-Western: 4
  • Co-crystal Structure: 1
  • Co-fractionation: 1
  • Reconstituted Complex: 2
  • Two-hybrid: 1

Genetic Interactions
  • Dosage Rescue: 7
  • Phenotypic Enhancement: 2
  • Positive Genetic: 1
  • Synthetic Growth Defect: 3
  • Synthetic Lethality: 2
  • Synthetic Rescue: 2

Expression Summary
Length (a.a.) 538
Molecular Weight (Da) 58,237
Isoelectric Point (pI) 4.78
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrVIII:227141 to 225525 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Last Update Coordinates: 2011-02-03 | Sequence: 2003-09-22
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..1617 227141..225525 2011-02-03 2003-09-22
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000001106

SSZ1 encodes a protein with sequence similarity to the HSP70 family of molecular chaperones (2). HSP70 is a large family of proteins that has been evolutionarily conserved from bacteria (DnaK) to humans (HSP72/73). HSP70 proteins were originally classified based upon their induction by heat shock and their size of ~70kDa (reviewed in 6). S. cerevisiae has at least 9 cytosolic forms of HSP70 (SSA1, SSA2, SSA3, SSA4, SSB1, SSB2, SSE1, SSE2, SSZ1), 2 HSP70s which are found in the endoplasmic reticulum (KAR2, LHS1), and 3 mitochondrial HSP70 proteins (SSC1, SSQ1, ECM10).

The activity of Ssz1p is localized to the ribosome where it functions as part of the ribosome-associated complex (RAC), which includes Ssz1p, the DnaJ homolog Zuo1p, and either Ssb1p or Ssb2p (1). RAC binds both the active ribosome and the associated nascent polypeptide chain to assist in translational fidelity and in proper protein folding (7, 8).

Like all other HSP70 proteins, Ssz1p contains an N-terminal ATPase domain and a C-terminal peptide-binding domain (2). However, unlike typical HSP70 proteins, neither the ATPase nor peptide-binding activities appear to be necessary for Ssz1p function (5, 9). Instead, it has been suggested that the role of Ssz1p is not to bind unfolded peptides, but to facilitate the ATPase-stimulating activity of Zuo1p on Ssb1p and Ssb2p, as Ssz1p is required for this stimulation in vitro (5). Loss of any of the RAC proteins results in the same phenotype: sensitivities to cold, high osmolarity, and translation-impairing drugs (9, 7). Unrelated to RAC activity, overexpression of Ssz1p results in pleiotropic drug resistance due to a Pdr1p-mediated upregulation of transcription of PDR5 and YOR1 (2).

Last updated: 2006-02-07 Contact SGD

References cited on this page View Complete Literature Guide for SSZ1
1) Gautschi M, et al.  (2001) RAC, a stable ribosome-associated complex in yeast formed by the DnaK-DnaJ homologs Ssz1p and zuotin. Proc Natl Acad Sci U S A 98(7):3762-7
2) Hallstrom TC, et al.  (1998) Regulation of transcription factor Pdr1p function by an Hsp70 protein in Saccharomyces cerevisiae. Mol Cell Biol 18(3):1147-55
3) Hallstrom TC and Moye-Rowley WS  (2000) Hyperactive forms of the Pdr1p transcription factor fail to respond to positive regulation by the hsp70 protein Pdr13p. Mol Microbiol 36(2):402-13
4) Eisenman HC and Craig EA  (2004) Activation of pleiotropic drug resistance by the J-protein and Hsp70-related proteins, Zuo1 and Ssz1. Mol Microbiol 53(1):335-44
5) Huang P, et al.  (2005) The Hsp70 Ssz1 modulates the function of the ribosome-associated J-protein Zuo1. Nat Struct Mol Biol 12(6):497-504
6) Bukau B and Horwich AL  (1998) The Hsp70 and Hsp60 chaperone machines. Cell 92(3):351-66
7) Gautschi M, et al.  (2002) A functional chaperone triad on the yeast ribosome. Proc Natl Acad Sci U S A 99(7):4209-14
8) Rakwalska M and Rospert S  (2004) The ribosome-bound chaperones RAC and Ssb1/2p are required for accurate translation in Saccharomyces cerevisiae. Mol Cell Biol 24(20):9186-97
9) Hundley H, et al.  (2002) The in vivo function of the ribosome-associated Hsp70, Ssz1, does not require its putative peptide-binding domain. Proc Natl Acad Sci U S A 99(7):4203-8