Gene Ontology annotation through association of InterPro records with GO terms
Annotation inferences using phylogenetic trees
Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt
Electronic Gene Ontology annotations created by ARBA machine learning models
Combined Automated Annotation using Multiple IEA Methods
Cooperation of the molecular chaperone Ydj1 with specific Hsp70 homologs to suppress protein aggregation.
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Ydj1 cooperated with Ssa Hsp70 proteins in the prevention of protein aggregation
"Ydj1p cooperated with Ssa Hsp70 proteins in the prevention of protein aggregation, but not with the Ssb Hsp70 proteins."
Molecular evolution of the HSP70 multigene family.
Functional interaction of cytosolic hsp70 and a DnaJ-related protein, Ydj1p, in protein translocation in vivo.
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SSA-deficient mutants show translocation defects for specific ER-targeted proteins
"Of six proteins destined for the endoplasmic reticulum, the translocation of only prepro-alpha-factor and proteinase A was inhibited"
Members of the Hsp70 family of proteins in the cell wall of Saccharomyces cerevisiae.
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Identified SSA2 in the cell wall and confirmed cytoplasmic localization
"the heat shock protein 70 (Hsp70) products of these genes, previously thought to be restricted to the cell interior, are also present in the cell wall"
The refolding activity of the yeast heat shock proteins Ssa1 and Ssa2 defines their role in protein translocation.
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Demonstrated Ssa1/2 refolding activity with denatured luciferase
"Depletion of Ssa1/2p had no effect on the ability of the yeast lysate to synthesize enzymatically active luciferase, but had a dramatic effect on the ability of the lysate to refold chemically denatured luciferase."
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Found Ssa1/2 depletion does not affect translocation in vitro
"Depletion of Ssa1/2p had no effect on the efficiency of translocation in this in vitro assay."
Role of Hsp70 subfamily, Ssa, in protein folding in yeast cells, seen in luciferase-transformed ssa mutants.
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Demonstrated SSA proteins are needed for protein folding in vivo
"The luciferase activity was significantly lower in ssa1ssa2 transformants than in the wild type (wt) cell transformed with the same plasmid."
Molecular mechanism governing heme signaling in yeast: a higher-order complex mediates heme regulation of the transcriptional activator HAP1.
Folding in vivo of a newly translated yeast cytosolic enzyme is mediated by the SSA class of cytosolic yeast Hsp70 proteins.
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SSA class Hsp70s assist de novo folding of newly translated cytosolic enzymes
"These findings indicate that, in vivo, the Hsp70 system assists in folding at least some newly translated cytosolic enzymes, most likely functioning in a posttranslational manner."
Cns1 is an essential protein associated with the hsp90 chaperone complex in Saccharomyces cerevisiae that can restore cyclophilin 40-dependent functions in cpr7Delta cells.
Cytosolic Hsp70s are involved in the transport of aminopeptidase 1 from the cytoplasm into the vacuole.
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SSA2 involved in Ape1 transport to vacuole and localizes to vacuole membrane
"Ssa1/2p was prominently localized to the vacuolar membrane, consistent with the role we propose for Ssa proteins in the fusion of transport vesicles with the vacuolar membrane."
The heat shock protein Ssa2p is required for import of fructose-1,6-bisphosphatase into Vid vesicles.
Global analysis of protein expression in yeast.
The ctf13-30/CTF13 genomic haploinsufficiency modifier screen identifies the yeast chromatin remodeling complex RSC, which is required for the establishment of sister chromatid cohesion.
A novel mode of chaperone action: heme activation of Hap1 by enhanced association of Hsp90 with the repressed Hsp70-Hap1 complex.
Navigating the chaperone network: an integrative map of physical and genetic interactions mediated by the hsp90 chaperone.
An integrated mass spectrometry-based proteomic approach: quantitative analysis of tandem affinity-purified in vivo cross-linked protein complexes (QTAX) to decipher the 26 S proteasome-interacting network.
Proteome survey reveals modularity of the yeast cell machinery.
Comparative analysis of Saccharomyces cerevisiae WW domains and their interacting proteins.
The plasma membrane proteome of Saccharomyces cerevisiae and its response to the antifungal calcofluor.
MMI1 (YKL056c, TMA19), the yeast orthologue of the translationally controlled tumor protein (TCTP) has apoptotic functions and interacts with both microtubules and mitochondria.
SGT2 and MDY2 interact with molecular chaperone YDJ1 in Saccharomyces cerevisiae.
Structure-templated predictions of novel protein interactions from sequence information.
An atlas of chaperone-protein interactions in Saccharomyces cerevisiae: implications to protein folding pathways in the cell.
Quantitative variations of the mitochondrial proteome and phosphoproteome during fermentative and respiratory growth in Saccharomyces cerevisiae.
Cytosolic Hsp70 and co-chaperones constitute a novel system for tRNA import into the nucleus.
The requirements of yeast Hsp70 of SSA family for the ubiquitin-dependent degradation of short-lived and abnormal proteins.
A novel assay provides insight into tRNAPhe retrograde nuclear import and re-export in S. cerevisiae.
RNA-dependent interactome allows network-based assignment of RNA-binding protein function.
The social and structural architecture of the yeast protein interactome.
Thermotolerance in S. cerevisiae as a model to study extracellular vesicle biology.
Candida albicans Ssa1/2p is the cell envelope binding protein for human salivary histatin 5.
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S. cerevisiae SSA1/SSA2 mutants show that Ssa1 and Ssa2 contribute to cell-envelope histatin 5 binding and fungicidal susceptibility.
"This study provides evidence for a novel function for yeast Ssa1/2 proteins as cell envelope binding receptors for Hst 5 that mediate fungicidal activity."
OpenScientist assessment of SSA2 plasma-membrane localization as non-core
Current PTHR19375 PAINT annotation snapshot
Falcon deep research report on SSA2 (Saccharomyces cerevisiae, UniProt P10592/YLL024C)
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SSA2 (YLL024C) encodes Ssa2, a cytosolic Hsp70 (Stress-Seventy subfamily A) chaperone; it is one of four cytosolic Ssa isoforms (Ssa1-4), with Ssa1/Ssa2 constitutively expressed and Ssa3/Ssa4 stress-inducible.
"In the retrieved literature, SSA2 is consistently described as one of four cytosolic Ssa Hsp70 isoforms (Ssa1–4), with **Ssa1/Ssa2 constitutively expressed** and **Ssa3/Ssa4 stress-inducible**, matching the UniProt-provided identity and family assignment."
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SSA2 is an ATP-dependent molecular chaperone of the Hsp70 family that performs ATP-driven cycles of client binding and release to prevent aggregation and promote folding/refolding and quality control, rather than catalyzing a metabolic reaction.
"**SSA2 encodes an ATP-dependent molecular chaperone of the Hsp70 family.** Rather than catalyzing a metabolic reaction with a defined substrate/product, Ssa2 performs **ATP-driven cycles of client binding and release** to prevent aggregation and promote folding/refolding and quality control."
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The N-terminal nucleotide-binding domain (NBD) mediates ATPase-cycle control (the Hsp40 cochaperone Ydj1 binds the NBD to stimulate ATPase activity), while the C-terminal region contributes to substrate transfer and isoform specificity.
"The **N-terminal nucleotide-binding domain (NBD)** is implicated in ATPase-cycle control (Ydj1 binds the NBD to stimulate ATPase activity)."
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SSA2 functions within the Hsp70-Hsp90 chaperone pathway; Ydj1 recruits misfolded clients to Hsp70 and transfers them preferentially to Ssa2 (over Ssa4), supporting subsequent Hsp90 engagement and client maturation.
"Using v-Src as an Hsp90 client, Gaur et al. show that the Hsp40 cochaperone **Ydj1 binds misfolded client, recruits it to Hsp70, and transfers it preferentially to Ssa2** (relative to Ssa4). Transfer to Ssa2 supports subsequent engagement with Hsp90 and client maturation."
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Ssa isoforms are not fully redundant; Ydj1-assisted luciferase refolding was ~25-30-fold higher with Ssa2 than with Ssa4, reflecting stronger Ydj1-Ssa2 functional coupling.
"Ydj1-assisted luciferase refolding activity was reported as **~25–30-fold higher with Ssa2 than with Ssa4**, consistent with stronger Ydj1–Ssa2 functional coupling."
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Ssa2 is localized predominantly to the cytosol; tagged Ssa proteins including Ssa2 show predominantly diffuse cytosolic distribution by fluorescence microscopy.
"Fluorescence microscopy of N-terminally tagged Ssa proteins (including **Ssa2**) shows predominantly **diffuse** signal in most cells, supporting predominant **cytosolic localization** under those conditions."
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Ssa1/Ssa2 are required for formation/localization of the cytoplasmic JUNQ compartment adjacent to the nucleus-vacuole junction (NVJ) and for degradation of cytoplasmic misfolded proteins routed there; loss of both shifts handling toward peripheral IPOD-like inclusions and inhibits clearance of a misfolded reporter.
"Ssa1/Ssa2 are required for formation/localization of the cytoplasmic **JUNQ** compartment adjacent to the **nucleus–vacuole junction (NVJ)** and for degradation of cytoplasmic misfolded proteins that are routed there."
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In a 2024 heat-shock-response feedback study, SSA2 had the highest expression rank among SSA paralogs (Ssa3 < Ssa4 < Ssa1 < Ssa2), and deleting its Hsf1-binding site (ssa2-deltaHSE) elevated basal HSE-YFP reporter and reduced heat-shock induction, consistent with SSA2 contributing to basal repression/feedback of the Hsf1 regulon.
"Disrupting the Hsf1-binding site in SSA2 (**ssa2ΔHSE**) was associated with **elevated basal HSE-YFP reporter** and **reduced induction after prolonged heat shock**, and the authors interpret the reduced induction as explained by the increased basal reporter level—consistent with SSA2 contributing to basal repression/feedback behavior in the Hsf1 regulon context."