MRPS9: Mitochondrial Ribosomal Protein S9
A nuclear-encoded component of the mitochondrial small ribosomal subunit essential for intra-mitochondrial protein synthesis.
Gene Information Card
| Symbol | MRPS9 |
|---|---|
| Full Name | Mitochondrial Ribosomal Protein S9 |
| Gene Type | Protein coding |
| Chromosomal Location | 2q12.1 |
| NCBI Gene ID | 64965 ncbi.nlm.nih.gov/gene/64965 |
| Ensembl ID | ENSG00000135972 |
| UniProt ID | P82933 |
| OMIM ID | 611982 |
| HGNC ID | 14493 |
| Aliases | S9mt, MRP-S9, RPMS9 |
Description
MRPS9 encodes a 28S mitochondrial ribosomal small subunit protein (S9). As a component of the mitochondrial ribosome (mitoribosome), it participates in the translation of 13 essential subunits of the oxidative phosphorylation (OXPHOS) complexes encoded by the mitochondrial genome. The protein is nuclear-encoded, synthesized in the cytosol, and imported into the mitochondrial matrix.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Combined oxidative phosphorylation deficiency (COXPD) | Loss-of-function mutations in MRPS9 impair mitochondrial translation, leading to reduced assembly and activity of OXPHOS complexes I, III, IV, and V. | ClinVar, OMIM |
| Mitochondrial encephalopathy | Deficient mitochondrial protein synthesis due to MRPS9 variants can cause neurological symptoms including seizures and developmental delay. | ClinVar, OMIM |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Heart | 12.5 | Medium |
| Skeletal muscle | 10.8 | Medium |
| Liver | 8.2 | Medium |
| Brain | 7.1 | Medium |
| Kidney | 6.9 | Medium |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HeLa | 14.3 | High expression |
| HEK293 | 12.1 | High expression |
| K562 | 9.5 | Medium expression |
| HepG2 | 8.8 | Medium expression |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.322C>T (p.Arg108Trp) | Missense | Rare | Loss of function; reduced mitoribosome assembly |
| c.463_464del (p.Leu155Valfs*3) | Frameshift | Rare | Loss of function; premature truncation |
| c.1A>G (p.Met1Val) | Start loss | Rare | Loss of function; translation initiation failure |
Mutation functional classification
Loss of Function (LOF)
Most reported MRPS9 variants are loss-of-function, leading to decreased mitochondrial translation and OXPHOS deficiency.
Gain of Function (GOF)
No gain-of-function mutations have been reported for MRPS9.
Dominant Negative (DN)
No dominant-negative mutations have been described for MRPS9.
View complete mutation data：
Gene Ontology (GO)
| • structural constituent of ribosome (GO:0003735) | • mitochondrial small ribosomal subunit (GO:0005763) |
| • mitochondrial translation (GO:0032543) | • mitochondrion (GO:0005739) |
Pathways
• Mitochondrial translation (Reactome: R-HSA-5368287)
• Respiratory electron transport (Reactome: R-HSA-611105)
Protein Summary
MRPS9 is a 396-amino-acid protein (UniProt P82933) that forms part of the 28S small subunit of the mitochondrial ribosome. It is essential for decoding mitochondrial mRNAs and synthesizing 13 OXPHOS subunits. The protein contains a mitochondrial targeting presequence that is cleaved upon import. Structural studies show it interacts with other mitoribosomal proteins and the 12S rRNA.
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