SAR1B Gene - Secretion Associated Ras Related GTPase 1B
Key regulator of COPII vesicle-mediated ER-to-Golgi transport
Gene Information Card
| Symbol | SAR1B |
|---|---|
| Full Name | Secretion Associated Ras Related GTPase 1B |
| Gene Type | protein-coding |
| Chromosomal Location | 5q31.1 |
| NCBI Gene ID | 51128 ncbi.nlm.nih.gov/gene/51128 |
| Ensembl ID | ENSG00000113522 |
| UniProt ID | Q9Y6B6 |
| OMIM ID | 607690 |
| HGNC ID | 10535 |
| Aliases | SAR1, SARA1, SARB, GTBPB |
Description
The SAR1B gene encodes a small GTPase that is a core component of the COPII coat complex, which mediates the budding of vesicles from the endoplasmic reticulum (ER) for transport to the Golgi apparatus. SAR1B cycles between an inactive GDP-bound and active GTP-bound form, regulating the assembly and disassembly of the COPII coat. Mutations in SAR1B cause chylomicron retention disease (Anderson disease), a disorder of intestinal fat malabsorption.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Chylomicron retention disease (Anderson disease) | Loss-of-function mutations in SAR1B impair COPII vesicle formation, blocking the export of chylomicrons from intestinal enterocytes, leading to fat malabsorption and failure to thrive. | OMIM #246700; ClinVar |
| Hypertriglyceridemia, familial | Rare SAR1B variants may contribute to altered lipid metabolism and elevated triglycerides. | ClinVar; PubMed |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Small intestine | 12.5 | Medium |
| Pancreas | 8.3 | Medium |
| Liver | 6.1 | Medium |
| Adipose tissue | 4.2 | Low |
| Colon | 3.8 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| Caco-2 (intestinal) | 15.2 | High expression; relevant for chylomicron studies |
| HepG2 (liver) | 7.8 | Moderate expression |
| HeLa (cervical) | 5.1 | Low expression |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.535C>T (p.Arg179Trp) | Missense | Rare | Loss of GTP binding; causes chylomicron retention disease |
| c.340G>A (p.Gly114Arg) | Missense | Rare | Impaired COPII coat assembly; associated with Anderson disease |
| c.1A>G (p.Met1Val) | Start loss | Rare | Complete loss of protein; severe phenotype |
Mutation functional classification
Loss of Function (LOF)
Most SAR1B mutations are loss-of-function, leading to defective COPII vesicle formation and impaired chylomicron export.
Gain of Function (GOF)
No gain-of-function mutations reported.
Dominant Negative (DN)
Some missense mutations may act in a dominant-negative manner by interfering with wild-type SAR1B function.
View complete mutation data：
Gene Ontology (GO)
| • GTPase activity | • COPII vesicle coating |
| • ER-to-Golgi vesicle-mediated transport | • small GTPase mediated signal transduction |
| • intracellular protein transport |
Pathways
• COPII-mediated vesicle transport
• ER-to-Golgi anterograde transport
• Chylomicron assembly and secretion
Protein Summary
SAR1B is a 198-amino acid small GTPase (21.8 kDa) that localizes to the ER membrane. It recruits the COPII coat components Sec23/24 and Sec13/31 upon GTP binding, initiating vesicle budding. The protein is highly expressed in tissues with active secretion, such as the small intestine and pancreas.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| SAR1B Knockout HEK293 Cell Line | EDJ-KQ2941 | Human | 51128 | Details Get a Quote |
| SAR1B Knockout A-549 Cell Line | EDJ-KQ24060 | Human | 51128 | Details Get a Quote |
| SAR1B Knockout HCT 116 Cell Line | EDJ-KQ24061 | Human | 51128 | Details Get a Quote |
| SAR1B Knockout HeLa Cell Line | EDJ-KQ24062 | Human | 51128 | Details Get a Quote |
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