STT3B
Subunit of the Oligosaccharyltransferase Complex
Gene Information Card
| Symbol | STT3B |
|---|---|
| Full Name | STT3 oligosaccharyltransferase complex catalytic subunit B |
| Gene Type | Protein coding |
| Chromosomal Location | 3p23 |
| NCBI Gene ID | 201595 ncbi.nlm.nih.gov/gene/201595 |
| Ensembl ID | ENSG00000163527 |
| UniProt ID | Q8TCJ2 |
| OMIM ID | 608605 |
| HGNC ID | 30611 |
| Aliases | STT3-B, SIMP, CDG2X |
Description
STT3B encodes a catalytic subunit of the oligosaccharyltransferase (OST) complex, which catalyzes the transfer of a 14-sugar oligosaccharide from dolichol to asparagine residues of nascent polypeptides during N-linked glycosylation. STT3B is one of two catalytic isoforms (STT3A and STT3B) and is particularly important for post-translational glycosylation of acceptor sites that are not efficiently modified by STT3A. Mutations in STT3B cause congenital disorder of glycosylation type IIx (STT3B-CDG).
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Congenital disorder of glycosylation type IIx (STT3B-CDG) | Loss-of-function mutations in STT3B impair N-glycosylation, leading to multisystem disease. | OMIM #608605; PMID: 23352259 |
| Colorectal cancer | Somatic mutations and altered expression of STT3B may contribute to tumor progression via aberrant glycosylation. | COSMIC; PMID: 29127259 |
| Hepatocellular carcinoma | STT3B overexpression associated with poor prognosis and altered N-glycosylation of surface proteins. | PMID: 32015549 |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Liver | 14.2 | Medium |
| Pancreas | 11.8 | Medium |
| Kidney | 9.5 | Medium |
| Brain | 6.3 | Low |
| Heart | 5.1 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HepG2 | 16.7 | Hepatocellular carcinoma cell line |
| HeLa | 12.4 | Cervical adenocarcinoma cell line |
| K-562 | 8.9 | Chronic myelogenous leukemia cell line |
| A549 | 7.2 | Lung carcinoma cell line |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.962G>A (p.Arg321Gln) | Missense | Rare | Loss of function; associated with STT3B-CDG |
| c.1280T>C (p.Leu427Pro) | Missense | Rare | Loss of function; associated with STT3B-CDG |
| c.1693C>T (p.Arg565Trp) | Missense | Somatic (COSMIC) | Unknown functional effect; found in colorectal cancer |
Mutation functional classification
Loss of Function (LOF)
Missense mutations (e.g., p.Arg321Gln, p.Leu427Pro) reduce or abolish OST catalytic activity, leading to hypoglycosylation.
Gain of Function (GOF)
Not reported.
Dominant Negative (DN)
Not reported.
View complete mutation data：
Gene Ontology (GO)
| • oligosaccharyl transferase activity (GO:0004576) | • protein N-linked glycosylation (GO:0006487) |
| • oligosaccharyltransferase complex (GO:0008250) | • integral component of membrane (GO:0016021) |
Pathways
• REACT:21367 - N-glycan biosynthesis
• KEGG:00510 - N-Glycan biosynthesis
• Reactome: R-HSA-446203 - Asparagine N-linked glycosylation
Protein Summary
STT3B is a 827-amino acid transmembrane protein localized to the endoplasmic reticulum. It serves as the catalytic subunit of the OST complex, specifically mediating post-translational N-glycosylation of acceptor sites that are skipped by STT3A. The protein contains a C-terminal catalytic domain and multiple transmembrane helices. STT3B is essential for proper glycosylation of a subset of glycoproteins, and its deficiency leads to a congenital disorder of glycosylation.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| STT3B Knockout HEK293 Cell Line | EDJ-KQ2807 | Human | 201595 | Details Get a Quote |
| STT3B Knockout A-549 Cell Line | EDJ-KQ23752 | Human | 201595 | Details Get a Quote |
| STT3B Knockout HCT 116 Cell Line | EDJ-KQ23753 | Human | 201595 | Details Get a Quote |
| STT3B Knockout HeLa Cell Line | EDJ-KQ23754 | Human | 201595 | Details Get a Quote |
