SSQ1/YLR369W Summary Help

Standard Name SSQ1 1
Systematic Name YLR369W
Alias SSC2 2 , SSH1 3
Feature Type ORF, Verified
Description Mitochondrial hsp70-type molecular chaperone; required for assembly of iron/sulfur clusters into proteins at a step after cluster synthesis, and for maturation of Yfh1p, which is a homolog of human frataxin implicated in Friedreich's ataxia (2, 4 and see Summary Paragraph)
Name Description Stress-Seventy subfamily Q
Chromosomal Location
ChrXII:859552 to 861525 | ORF Map | GBrowse
Gene Ontology Annotations All SSQ1 GO evidence and references
  View Computational GO annotations for SSQ1
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 2 genes
Classical genetics
Large-scale survey
31 total interaction(s) for 21 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 7
  • Affinity Capture-RNA: 1
  • Affinity Capture-Western: 4
  • Reconstituted Complex: 2
  • Two-hybrid: 2

Genetic Interactions
  • Dosage Lethality: 1
  • Dosage Rescue: 4
  • Phenotypic Enhancement: 1
  • Synthetic Growth Defect: 1
  • Synthetic Haploinsufficiency: 1
  • Synthetic Lethality: 4
  • Synthetic Rescue: 3

Expression Summary
Length (a.a.) 657
Molecular Weight (Da) 72,364
Isoelectric Point (pI) 6.3
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrXII:859552 to 861525 | ORF Map | GBrowse
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..1974 859552..861525 2011-02-03 1996-07-31
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 SGDIDS000004361

SSC1, SSQ1, and ECM10 encode chaperone proteins of the HSP70 family that localize to the mitochondria (5 and reviewed in 6). In addition to these three mitochondrial HSP70s, S. cerevisiae cells also synthesize nine cytosolic HSPs (encoded by SSA1, SSA2, SSA3, SSA4, SSB1, SSB2, SSE1, SSE2, SSZ1) and two that are found in the ER (KAR2, LHS1). 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. The main function of these proteins is to serve as molecular chaperones, binding unfolded peptides to assist in proper folding and prevent aggregation/misfolding (reviewed in 7 and 8). HSP70s are also involved in disassembling aggregates of misfolded proteins, translocating select proteins into the mitochondria and ER, and degrading aberrant proteins (reviewed in 9, 8, and 7).

Like all other Hsp70 proteins, Ssq1p contains an N-terminal ATPase domain and a C-terminal peptide-binding domain, and binds to unfolded peptides in an ATP-regulated manner (3, 10). The ATPase activity of Ssq1p is cooperatively stimulated by the DnaJ/HSP40 co-chaperone Jac1p and the Fe/S cluster scaffolding protein Isu1p (11). Subsequent ADP-ATP exchange is promoted by the nucleotide exchange factor Mge1p (10). Ssq1p is responsible for mediating the assembly/maturation of mitochondrial proteins containing iron-sulfur (Fe/S) clusters (1, 11). In particular, Ssq1p has been shown to process the maturation of Yfh1p, the yeast homolog of the human protein frataxin, which is involved in the neurodegenerative disease Friedreich's ataxia (OMIM; 2, 12). Loss of Ssq1p results in increased cellular iron uptake, accumulation of mitochondrial iron, cold-sensitivity, and a decrease in enzyme activity of mitochondrial proteins containing an Fe/S center (1, 2, 3).

Last updated: 2006-02-09 Contact SGD

References cited on this page View Complete Literature Guide for SSQ1
1) Strain J, et al.  (1998) Suppressors of superoxide dismutase (SOD1) deficiency in Saccharomyces cerevisiae. Identification of proteins predicted to mediate iron-sulfur cluster assembly. J Biol Chem 273(47):31138-44
2) Knight SA, et al.  (1998) Mt-Hsp70 homolog, Ssc2p, required for maturation of yeast frataxin and mitochondrial iron homeostasis. J Biol Chem 273(29):18389-93
3) Schilke B, et al.  (1996) The cold sensitivity of a mutant of Saccharomyces cerevisiae lacking a mitochondrial heat shock protein 70 is suppressed by loss of mitochondrial DNA. J Cell Biol 134(3):603-13
4) Muhlenhoff U, et al.  (2003) Components involved in assembly and dislocation of iron-sulfur clusters on the scaffold protein Isu1p. EMBO J 22(18):4815-25
5) Baumann F, et al.  (2000) Ecm10, a novel hsp70 homolog in the mitochondrial matrix of the yeast Saccharomyces cerevisiae. FEBS Lett 487(2):307-12
6) Voos W and Rottgers K  (2002) Molecular chaperones as essential mediators of mitochondrial biogenesis. Biochim Biophys Acta 1592(1):51-62
7) Bukau B and Horwich AL  (1998) The Hsp70 and Hsp60 chaperone machines. Cell 92(3):351-66
8) Becker J and Craig EA  (1994) Heat-shock proteins as molecular chaperones. Eur J Biochem 219(1-2):11-23
9) Hartl FU  (1996) Molecular chaperones in cellular protein folding. Nature 381(6583):571-9
10) Schmidt S, et al.  (2001) The two mitochondrial heat shock proteins 70, Ssc1 and Ssq1, compete for the cochaperone Mge1. J Mol Biol 313(1):13-26
11) Dutkiewicz R, et al.  (2003) Ssq1, a mitochondrial Hsp70 involved in iron-sulfur (Fe/S) center biogenesis. Similarities to and differences from its bacterial counterpart. J Biol Chem 278(32):29719-27
12) Voisine C, et al.  (2000) Role of the mitochondrial Hsp70s, Ssc1 and Ssq1, in the maturation of Yfh1. Mol Cell Biol 20(10):3677-84