P11484 · SSB1_YEAST
- ProteinRibosome-associated molecular chaperone SSB1
- GeneSSB1
- StatusUniProtKB reviewed (Swiss-Prot)
- Amino acids613 (go to sequence)
- Protein existenceEvidence at protein level
- Annotation score5/5
Function
function
Ribosome-bound, Hsp70-type chaperone that assists in the cotranslational folding of newly synthesized proteins in the cytosol. Stimulates folding by interacting with nascent chains, binding to short, largely hydrophobic sequences exposed by unfolded proteins, thereby stabilizing longer, more slowly translated, and aggregation-prone nascent polypeptides and domains that cannot fold stably until fully synthesized. The Hsp70-protein substrate interaction depends on ATP-binding and on allosteric regulation between the NBD and the SBD. The ATP-bound state is characterized by a fast exchange rate of substrate (low affinity state), while in the ADP-bound state exchange is much slower (high affinity state). During the Hsp70 cycle, the chaperone switches between the ATP-bound state (open conformation) and the ADP-bound state (closed conformation) by major conformational rearrangements involving mainly the lid domain. Ssb cooperates with a specific Hsp40/Hsp70 co-chaperone termed the ribosome-associated complex (RAC), which stimulates the ATPase activity of the ribosome-associated pool of Ssbs and switches it to the high affinity substrate binding state. Hsp110 chaperone SSE1 and FES1 act as nucleotide exchange factors that cause substrate release.
Miscellaneous
Present with 170000 molecules/cell in log phase SD medium.
Catalytic activity
- ATP + H2O = ADP + H+ + phosphate
Kinetics
KM | SUBSTRATE | pH | TEMPERATURE[C] | NOTES | EVIDENCE | |
---|---|---|---|---|---|---|
270 μM | ATP (at 2.5 mM potassium acetate) | |||||
147 μM | ATP (at 100 mM potassium acetate) |
kcat is 0.95 min-1 with ATP as substrate (at 2.5 mM potassium acetate) and 0.81 min-1 with ATP as substrate (at 100 mM potassium acetate).
Features
Showing features for binding site.
GO annotations
Aspect | Term | |
---|---|---|
Cellular Component | cytoplasm | |
Cellular Component | cytosol | |
Cellular Component | nucleus | |
Cellular Component | plasma membrane | |
Molecular Function | ATP binding | |
Molecular Function | ATP hydrolysis activity | |
Molecular Function | ATP-dependent protein folding chaperone | |
Molecular Function | calmodulin binding | |
Molecular Function | heat shock protein binding | |
Molecular Function | protein folding chaperone | |
Molecular Function | unfolded protein binding | |
Biological Process | 'de novo' cotranslational protein folding | |
Biological Process | chaperone cofactor-dependent protein refolding | |
Biological Process | cytoplasmic translation | |
Biological Process | protein refolding | |
Biological Process | regulation of translational fidelity | |
Biological Process | ribosomal subunit export from nucleus | |
Biological Process | rRNA processing | |
Biological Process | translational frameshifting | |
Biological Process | translational termination |
Keywords
- Molecular function
- Biological process
- Ligand
Enzyme and pathway databases
Names & Taxonomy
Protein names
- Recommended nameRibosome-associated molecular chaperone SSB1
- EC number
- Alternative names
Gene names
Organism names
- Strains
- Taxonomic lineageEukaryota > Fungi > Dikarya > Ascomycota > Saccharomycotina > Saccharomycetes > Saccharomycetales > Saccharomycetaceae > Saccharomyces
Accessions
- Primary accessionP11484
- Secondary accessions
Proteomes
Organism-specific databases
Subcellular Location
UniProt Annotation
GO Annotation
Note: About 50% of the protein is associated with translating ribosomes, but sufficient Ssb exists in the cell for each ribosome to be associated with at least one Ssb molecule.
Keywords
- Cellular component
Phenotypes & Variants
Features
Showing features for mutagenesis.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Mutagenesis | 73 | Unable to hydrolyze ATP and moderately reduces ribosome binding. | ||||
Sequence: K → A | ||||||
Mutagenesis | 567-568 | In SSB1-L(BC): Reduces ribosome-binding to less than 50%. | ||||
Sequence: KR → EE | ||||||
Mutagenesis | 596-597 | In SSB1-D1: Reduces ribosome-binding to less than 50%. | ||||
Sequence: RK → DD | ||||||
Mutagenesis | 603-604 | In SSB1-D2: Reduces ribosome-binding to less than 50%. | ||||
Sequence: KR → DD |
PTM/Processing
Features
Showing features for initiator methionine, modified residue, chain.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Initiator methionine | 1 | Removed | ||||
Sequence: M | ||||||
Modified residue | 2 | N-acetylalanine | ||||
Sequence: A | ||||||
Chain | PRO_0000078389 | 2-613 | Ribosome-associated molecular chaperone SSB1 | |||
Sequence: AEGVFQGAIGIDLGTTYSCVATYESSVEIIANEQGNRVTPSFVAFTPEERLIGDAAKNQAALNPRNTVFDAKRLIGRRFDDESVQKDMKTWPFKVIDVDGNPVIEVQYLEETKTFSPQEISAMVLTKMKEIAEAKIGKKVEKAVITVPAYFNDAQRQATKDAGAISGLNVLRIINEPTAAAIAYGLGAGKSEKERHVLIFDLGGGTFDVSLLHIAGGVYTVKSTSGNTHLGGQDFDTNLLEHFKAEFKKKTGLDISDDARALRRLRTAAERAKRTLSSVTQTTVEVDSLFDGEDFESSLTRARFEDLNAALFKSTLEPVEQVLKDAKISKSQIDEVVLVGGSTRIPKVQKLLSDFFDGKQLEKSINPDEAVAYGAAVQGAILTGQSTSDETKDLLLLDVAPLSLGVGMQGDMFGIVVPRNTTVPTIKRRTFTTCADNQTTVQFPVYQGERVNCKENTLLGEFDLKNIPMMPAGEPVLEAIFEVDANGILKVTAVEKSTGKSSNITISNAVGRLSSEEIEKMVNQAEEFKAADEAFAKKHEARQRLESYVASIEQTVTDPVLSSKLKRGSKSKIEAALSDALAALQIEDPSADELRKAEVGLKRVVTKAMSSR | ||||||
Modified residue | 47 | Phosphothreonine | ||||
Sequence: T | ||||||
Modified residue | 431 | Phosphothreonine | ||||
Sequence: T |
Keywords
- PTM
Proteomic databases
PTM databases
Expression
Induction
Expression decreases after heat shock or during growth to stationary phase (PubMed:2651414, PubMed:6761581).
Degraded during heat shock treatment (at protein level) (PubMed:7646503).
Up-regulated upon carbon upshift and down-regulated upon amino acid limitation in an HSF1-dependent manner (PubMed:10322015).
Degraded during heat shock treatment (at protein level) (PubMed:7646503).
Up-regulated upon carbon upshift and down-regulated upon amino acid limitation in an HSF1-dependent manner (PubMed:10322015).
Interaction
Subunit
Binds to ribosomes (PubMed:1394434, PubMed:27917864, PubMed:9670014).
Binds close to the ribosomal tunnel exit via contacts with both ribosomal proteins RPL35, RPL39 and RPL19, and rRNA (PubMed:27882919).
Directly interacts with nascent polypeptides. This interaction is dependent on the ribosome-associated complex (RAC) (PubMed:11929994, PubMed:23332755).
Interacts with SSE1 (PubMed:16219770, PubMed:16221677, PubMed:23332755).
Interacts with FES1 (PubMed:17132105).
Interacts with NAP1 (PubMed:18086883).
Binds close to the ribosomal tunnel exit via contacts with both ribosomal proteins RPL35, RPL39 and RPL19, and rRNA (PubMed:27882919).
Directly interacts with nascent polypeptides. This interaction is dependent on the ribosome-associated complex (RAC) (PubMed:11929994, PubMed:23332755).
Interacts with SSE1 (PubMed:16219770, PubMed:16221677, PubMed:23332755).
Interacts with FES1 (PubMed:17132105).
Interacts with NAP1 (PubMed:18086883).
Binary interactions
Type | Entry 1 | Entry 2 | Number of experiments | Intact | |
---|---|---|---|---|---|
BINARY | P11484 | BUD27 P43573 | 3 | EBI-8627, EBI-22787 | |
BINARY | P11484 | PFK26 P40433 | 2 | EBI-8627, EBI-1956 | |
BINARY | P11484 | SSE1 P32589 | 3 | EBI-8627, EBI-8648 | |
BINARY | P11484 | TOM71 P38825 | 2 | EBI-8627, EBI-24694 |
Protein-protein interaction databases
Miscellaneous
Structure
Family & Domains
Features
Showing features for region, motif.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Region | 2-391 | Nucleotide binding domain (NBD) | ||||
Sequence: AEGVFQGAIGIDLGTTYSCVATYESSVEIIANEQGNRVTPSFVAFTPEERLIGDAAKNQAALNPRNTVFDAKRLIGRRFDDESVQKDMKTWPFKVIDVDGNPVIEVQYLEETKTFSPQEISAMVLTKMKEIAEAKIGKKVEKAVITVPAYFNDAQRQATKDAGAISGLNVLRIINEPTAAAIAYGLGAGKSEKERHVLIFDLGGGTFDVSLLHIAGGVYTVKSTSGNTHLGGQDFDTNLLEHFKAEFKKKTGLDISDDARALRRLRTAAERAKRTLSSVTQTTVEVDSLFDGEDFESSLTRARFEDLNAALFKSTLEPVEQVLKDAKISKSQIDEVVLVGGSTRIPKVQKLLSDFFDGKQLEKSINPDEAVAYGAAVQGAILTGQSTSDE | ||||||
Region | 392-402 | Inter-domain linker | ||||
Sequence: TKDLLLLDVAP | ||||||
Region | 403-613 | Substrate binding domain (SBD) | ||||
Sequence: LSLGVGMQGDMFGIVVPRNTTVPTIKRRTFTTCADNQTTVQFPVYQGERVNCKENTLLGEFDLKNIPMMPAGEPVLEAIFEVDANGILKVTAVEKSTGKSSNITISNAVGRLSSEEIEKMVNQAEEFKAADEAFAKKHEARQRLESYVASIEQTVTDPVLSSKLKRGSKSKIEAALSDALAALQIEDPSADELRKAEVGLKRVVTKAMSSR | ||||||
Motif | 428-430 | Contributes to ribosome binding | ||||
Sequence: KRR | ||||||
Region | 516-612 | Lid domain (SBDalpha) | ||||
Sequence: SEEIEKMVNQAEEFKAADEAFAKKHEARQRLESYVASIEQTVTDPVLSSKLKRGSKSKIEAALSDALAALQIEDPSADELRKAEVGLKRVVTKAMSS | ||||||
Motif | 574-582 | Nuclear export signal | ||||
Sequence: IEAALSDAL | ||||||
Region | 601-613 | Required for interaction with ribosomes | ||||
Sequence: GLKRVVTKAMSSR |
Sequence similarities
Belongs to the heat shock protein 70 family. Ssb-type Hsp70 subfamily.
Phylogenomic databases
Family and domain databases
Sequence
- Sequence statusComplete
- Length613
- Mass (Da)66,602
- Last updated2007-01-23 v3
- ChecksumF16FA7C25A40321A
Features
Showing features for sequence conflict.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Sequence conflict | 180-184 | in Ref. 5; AAA34692 | ||||
Sequence: AAAIA → VVVIV | ||||||
Sequence conflict | 189 | in Ref. 5; AAA34692 | ||||
Sequence: A → V | ||||||
Sequence conflict | 192 | in Ref. 5; AAA34692 | ||||
Sequence: S → F |
Keywords
- Technical term
Sequence databases
Nucleotide Sequence | Protein Sequence | Molecule Type | Status | |
---|---|---|---|---|
X13713 EMBL· GenBank· DDBJ | CAA31995.1 EMBL· GenBank· DDBJ | Genomic DNA | ||
M25395 EMBL· GenBank· DDBJ | AAA35099.1 EMBL· GenBank· DDBJ | mRNA | ||
Z74277 EMBL· GenBank· DDBJ | CAA98807.1 EMBL· GenBank· DDBJ | Genomic DNA | ||
AH001377 EMBL· GenBank· DDBJ | AAA34691.1 EMBL· GenBank· DDBJ | Genomic DNA | ||
AH001377 EMBL· GenBank· DDBJ | AAA34692.1 EMBL· GenBank· DDBJ | Genomic DNA | ||
BK006938 EMBL· GenBank· DDBJ | DAA11637.1 EMBL· GenBank· DDBJ | Genomic DNA |