SSM4/YIL030C Summary Help

Standard Name SSM4 1
Systematic Name YIL030C
Alias DOA10 , KIS3 2
Feature Type ORF, Verified
Description Ubiquitin-protein ligase involved in ER-associated protein degradation; located in the ER/nuclear envelope; ssm4 mutation suppresses mRNA instability caused by an rna14 mutation (1, 3 and see Summary Paragraph)
Name Description Suppressor of mrna Stability Mutant 1
Chromosomal Location
ChrIX:300009 to 296050 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Gene Ontology Annotations All SSM4 GO evidence and references
  View Computational GO annotations for SSM4
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 3 genes
Classical genetics
Large-scale survey
223 total interaction(s) for 163 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 9
  • Affinity Capture-RNA: 2
  • Affinity Capture-Western: 22
  • Biochemical Activity: 2
  • PCA: 2
  • Protein-peptide: 72
  • Reconstituted Complex: 1

Genetic Interactions
  • Dosage Lethality: 1
  • Negative Genetic: 37
  • Phenotypic Enhancement: 37
  • Phenotypic Suppression: 6
  • Positive Genetic: 14
  • Synthetic Growth Defect: 3
  • Synthetic Lethality: 6
  • Synthetic Rescue: 9

Expression Summary
Length (a.a.) 1,319
Molecular Weight (Da) 151,453
Isoelectric Point (pI) 6.22
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrIX:300009 to 296050 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Last Update Coordinates: 2011-02-03 | Sequence: 1994-12-10
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..3960 300009..296050 2011-02-03 1994-12-10
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | E.C. | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000001292

Ssm4p and Hrd1p are ubiquitin ligases (E3) involved in endoplasmic reticulum-associated degradation (ERAD) (4, 5, 3). Ssm4p and Hrd1p are central members of the ubiquitin ligase complexes that are responsible for recognizing and ubiquitinating misfolded proteins in the ER for degradation by the proteasome (6, 7, 8). Misfolded cytosolic proteins are ubiquitinated by Ssm4p whereas misfolded luminal and membrane proteins are ubiquitinated by Hrd1p (6, 7, 8). The Ssm4p and Hrd1p ubiquitin ligase complexes also localize to different regions along the ER-nuclear membrane system: Ssm4p localizes to the inner nuclear membrane while Hrd1p remains in the ER membrane (9). Despite these differences, Ssm4p and Hrd1p appear to have overlapping substrate specificities and redundant functionalities (3, 10). Each ubiquitin ligase complex interacts with the Cdc48p-Npl4p-Ufd1p AAA ATPase complex via Ubx2p in order to extract ubiquitinated substrates from the ER (6, 7, 8, and references within).

Last updated: 2008-02-11 Contact SGD

References cited on this page View Complete Literature Guide for SSM4
1) Mandart E, et al.  (1994) Inactivation of SSM4, a new Saccharomyces cerevisiae gene, suppresses mRNA instability due to rna14 mutations. Mol Gen Genet 245(3):323-33
2) Kopski KM and Huffaker TC  (1997) Suppressors of the ndc10-2 mutation: a role for the ubiquitin system in Saccharomyces cerevisiae kinetochore function. Genetics 147(2):409-20
3) Swanson R, et al.  (2001) A conserved ubiquitin ligase of the nuclear envelope/endoplasmic reticulum that functions in both ER-associated and Matalpha2 repressor degradation. Genes Dev 15(20):2660-74
4) Bays NW, et al.  (2001) Hrd1p/Der3p is a membrane-anchored ubiquitin ligase required for ER-associated degradation. Nat Cell Biol 3(1):24-9
5) Deak PM and Wolf DH  (2001) Membrane topology and function of Der3/Hrd1p as a ubiquitin-protein ligase (E3) involved in endoplasmic reticulum degradation. J Biol Chem 276(14):10663-9
6) Gauss R, et al.  (2006) A complex of Yos9p and the HRD ligase integrates endoplasmic reticulum quality control into the degradation machinery. Nat Cell Biol 8(8):849-54
7) Denic V, et al.  (2006) A luminal surveillance complex that selects misfolded glycoproteins for ER-associated degradation. Cell 126(2):349-59
8) Carvalho P, et al.  (2006) Distinct ubiquitin-ligase complexes define convergent pathways for the degradation of ER proteins. Cell 126(2):361-73
9) Deng M and Hochstrasser M  (2006) Spatially regulated ubiquitin ligation by an ER/nuclear membrane ligase. Nature 443(7113):827-31
10) Kota J, et al.  (2007) Membrane chaperone Shr3 assists in folding amino acid permeases preventing precocious ERAD. J Cell Biol 176(5):617-28