SAMM50: Sorting and Assembly Machinery Component 50 Homolog
Mitochondrial SAM Complex Subunit and Cristae Morphology Regulator
Gene Information Card
| Symbol | SAMM50 |
|---|---|
| Full Name | Sorting and Assembly Machinery Component 50 Homolog |
| Gene Type | Protein coding |
| Chromosomal Location | 22q13.31 |
| NCBI Gene ID | 25813 ncbi.nlm.nih.gov/gene/25813 |
| Ensembl ID | ENSG00000100347 |
| UniProt ID | Q9Y512 |
| OMIM ID | 612055 |
| HGNC ID | 24276 |
| Aliases | SAM50, CGI-51, OMP85, TOB55 |
Description
SAMM50 encodes the mitochondrial sorting and assembly machinery component 50, a central subunit of the SAM (Sorting and Assembly Machinery) complex located in the mitochondrial outer membrane. This protein is essential for the biogenesis of beta-barrel proteins of the mitochondrial outer membrane, including VDAC and Tom40, and plays a critical role in maintaining cristae morphology and mitochondrial protein import. SAMM50 is also involved in the regulation of TP53 stability and mitochondrial dynamics.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Hepatocellular carcinoma | SAMM50 overexpression promotes TP53 degradation via MDM2, leading to increased cell proliferation and tumor growth. | PMID: 31409831 |
| Mitochondrial disease (general) | Defects in SAM complex impair mitochondrial protein import and cristae formation, causing respiratory chain dysfunction. | PMID: 22995989 |
| Non-alcoholic fatty liver disease (NAFLD) | SAMM50 variants (e.g., rs738491) are associated with hepatic lipid accumulation and fibrosis progression. | PMID: 24627523 |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Liver | 14.2 | High |
| Heart | 10.8 | High |
| Kidney | 9.5 | Medium |
| Skeletal Muscle | 8.1 | Medium |
| Brain | 5.3 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HepG2 | 12.1 | Hepatocellular carcinoma cell line |
| HEK293 | 9.8 | Embryonic kidney cells |
| HeLa | 7.4 | Cervical cancer cells |
| K562 | 6.2 | Leukemia cells |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| rs738491 (intronic) | SNP | 0.32 (MAF in East Asians) | Associated with NAFLD risk |
| c.1012C>T (p.Arg338Trp) | Missense | <0.01 | Potential loss of function; reported in mitochondrial disease |
| c.1435G>A (p.Gly479Arg) | Missense | <0.01 | Impaired SAM complex assembly |
Mutation functional classification
Loss of Function (LOF)
Missense mutations (e.g., p.Arg338Trp) disrupt beta-barrel protein insertion and mitochondrial import, leading to cristae disorganization.
Gain of Function (GOF)
Not reported.
Dominant Negative (DN)
Not reported.
View complete mutation data：
Gene Ontology (GO)
| • Mitochondrial outer membrane translocase complex | • Protein insertion into mitochondrial outer membrane |
| • Protein targeting to mitochondrion | • Cristae formation |
| • Mitochondrial respiratory chain complex assembly |
Pathways
• Mitochondrial protein import (SAM complex)
• TP53 regulation by MDM2
Protein Summary
SAMM50 is a 50 kDa transmembrane protein of the mitochondrial outer membrane, forming a central channel for beta-barrel protein insertion. It interacts with metaxins (MTX1, MTX2) and the MICOS complex to maintain cristae junctions. The protein contains a POTRA domain and a beta-barrel domain, and its C-terminal region binds MDM2 to regulate TP53 stability.
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