SSBP1: Single-Stranded DNA Binding Protein 1
Mitochondrial SSB Protein – Key Role in mtDNA Replication and Repair
Gene Information Card
| Symbol | SSBP1 |
|---|---|
| Full Name | Single-Stranded DNA Binding Protein 1 |
| Gene Type | Protein coding |
| Chromosomal Location | 7q34 |
| NCBI Gene ID | 6742 ncbi.nlm.nih.gov/gene/6742 |
| Ensembl ID | ENSG00000106028 |
| UniProt ID | Q04837 |
| OMIM ID | 600439 |
| HGNC ID | 11322 |
| Aliases | SSB, mtSSB, SOSS-B1, NAD+-dependent DNA ligase |
Description
SSBP1 encodes the mitochondrial single-stranded DNA binding protein (mtSSB), which is essential for mitochondrial DNA (mtDNA) replication, repair, and maintenance. It binds to single-stranded DNA intermediates, protecting them from degradation and facilitating the action of DNA polymerase gamma. Mutations in SSBP1 cause mitochondrial disorders, including optic atrophy and mtDNA depletion syndromes.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Optic atrophy 13 (OPA13) | Loss-of-function mutations impair mtDNA replication, leading to retinal ganglion cell degeneration | ClinVar, OMIM |
| Mitochondrial DNA depletion syndrome (MDDS) | Defective mtSSB reduces mtDNA copy number, causing tissue-specific energy failure | ClinVar, PubMed |
| Progressive external ophthalmoplegia (PEO) | Dominant-negative mutations disrupt mtDNA maintenance, resulting in multiple mtDNA deletions | ClinVar, OMIM |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Liver | 12.5 | Medium |
| Heart | 10.8 | Medium |
| Skeletal muscle | 9.2 | Medium |
| Brain | 8.1 | Medium |
| Kidney | 7.6 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HeLa | 14.3 | High expression |
| HEK293 | 11.7 | Medium expression |
| HepG2 | 10.5 | Medium expression |
| K562 | 6.2 | Low expression |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.320A>G (p.Glu107Gly) | Missense | Rare | Reduced DNA binding affinity, dominant-negative effect |
| c.401C>T (p.Pro134Leu) | Missense | Rare | Impaired mtDNA replication, associated with OPA13 |
| c.1A>G (p.Met1?) | Start loss | Very rare | Complete loss of protein, mtDNA depletion |
Mutation functional classification
Loss of Function (LOF)
Homozygous or compound heterozygous loss-of-function mutations cause mtDNA depletion and severe mitochondrial disease.
Gain of Function (GOF)
Not reported for SSBP1.
Dominant Negative (DN)
Heterozygous missense mutations (e.g., p.Glu107Gly) act as dominant-negative, disrupting mtSSB tetramer formation and causing optic atrophy.
View complete mutation data：
Gene Ontology (GO)
| • single-stranded DNA binding (GO:0003697) | • mitochondrion (GO:0005739) |
| • DNA replication (GO:0006260) | • DNA repair (GO:0006281) |
| • mitochondrial nucleoid (GO:0042645) |
Pathways
• Mitochondrial DNA replication (Reactome: R-HSA-1592230)
• Mitochondrial genome maintenance (KEGG: hsa04932)
Protein Summary
SSBP1 encodes the mitochondrial single-stranded DNA binding protein (mtSSB), a 15.8 kDa protein that forms a stable homotetramer. It binds with high affinity to single-stranded DNA, protecting it from nucleases and recruiting DNA polymerase gamma during mtDNA replication. The protein is essential for maintaining mtDNA copy number and integrity. Mutations in SSBP1 lead to mitochondrial disorders, primarily affecting high-energy tissues such as the optic nerve and muscle.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| SSBP1 Knockout HEK293 Cell Line | EDJ-KQ5845 | Human | 6742 | Details Get a Quote |
| SSBP1 Knockout HCT 116 Cell Line | EDJ-KQ28044 | Human | 6742 | Details Get a Quote |
| SSBP1 Knockout A-549 Cell Line | EDJ-KQ29303 | Human | 6742 | Details Get a Quote |
| SSBP1 Knockout HeLa Cell Line | EDJ-KQ29305 | Human | 6742 | Details Get a Quote |
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