GO:0180057 protein post-translational transfer of dolichol-linked oligosaccharide: N-Glycosylation Pathway, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0180057 describes the co-translational transfer of a preassembled dolichol-linked oligosaccharide (LLO) precursor to an asparagine residue within the Asn-X-Ser/Thr motif of a nascent protein.
• This process is mediated by the oligosaccharyltransferase (OST) complex, specifically the OSTB complex, and represents a key step in N-linked protein glycosylation.
• The dolichol-linked oligosaccharide precursor is assembled on the endoplasmic reticulum membrane and then transferred en bloc to the target protein.
• Defects in this pathway can lead to a group of human diseases known as congenital disorders of glycosylation (CDGs), which affect multiple organ systems.
• Research into GO:0180057 relies on methods such as metabolic labeling, mass spectrometry, and CRISPR-based gene editing to dissect the molecular machinery.
• Understanding this process is critical for biotechnology applications, including the production of therapeutic glycoproteins with defined glycan structures.
Description
Protein glycosylation is one of the most common post-translational modifications and plays essential roles in protein folding, stability, and cell-cell communication. The term GO:0180057, protein post-translational transfer of dolichol-linked oligosaccharide, refers to a specific N-linked glycosylation process in which a preassembled dolichol-linked oligosaccharide (LLO) precursor is transferred co-translationally to an asparagine residue within the motif Asn-X-Ser/Thr of a target protein. This transfer is mediated by the OSTB complex, a member of the oligosaccharyltransferase (OST) family. The process is fundamental to the biogenesis of glycoproteins in the endoplasmic reticulum (ER) and is conserved across eukaryotes.
protein post-translational transfer of dolichol-linked oligosaccharide At A Glance
| GO ID | GO:0180057 |
|---|---|
| GO term | protein post-translational transfer of dolichol-linked oligosaccharide |
| Ontology | biological_process |
| Synonym | protein N-linked glycosylation via asparagine, post-translational; protein N-linked glycosylation via asparagine, posttranslational; protein posttranslational transfer of dolichol-linked oligosaccharide |
| Major function | Transfer of a preassembled dolichol-linked oligosaccharide to asparagine residues in nascent proteins, mediated by the OSTB complex |
| Cellular location | Endoplasmic reticulum membrane |
| Key enzyme complex | Oligosaccharyltransferase (OST), specifically OSTB |
| Substrate | Dolichol-linked oligosaccharide (LLO) precursor and nascent polypeptide |
| Product | N-glycosylated protein with a Glc3Man9GlcNAc2 glycan attached to asparagine |
What Is GO:0180057?
GO:0180057 is a biological process defined as the N-linked protein glycosylation step in which the preassembled dolichol-linked oligosaccharide precursor is transferred co-translationally to an asparagine residue within the motif Asn-X-Ser/Thr of a target protein, mediated by the OSTB complex. This process is also known as protein N-linked glycosylation via asparagine, post-translational or posttranslational.
Why Is protein post-translational transfer of dolichol-linked oligosaccharide Important in Cell Biology?
The transfer of the dolichol-linked oligosaccharide to proteins is a critical step in the N-glycosylation pathway, influencing protein folding, stability, and function. Defects in this process can lead to a range of human diseases, including congenital disorders of glycosylation (CDGs), which often present with neurological and developmental abnormalities. Moreover, the efficiency of this transfer affects the production of therapeutic glycoproteins in biotechnological settings.
• Essential for the biosynthesis of N-linked glycoproteins, which are involved in cell signaling, immune recognition, and structural integrity.
• Mutations in genes encoding components of the OST complex can cause CDGs, highlighting its clinical relevance.
• The process is conserved from yeast to humans, making model organisms valuable for studying its mechanism.
• Efficient N-glycosylation is required for the proper folding and secretion of many therapeutic proteins.
• Alterations in glycosylation patterns are associated with cancer progression and metastasis.
• Understanding the regulation of this process can inform the design of glycoengineered cell lines for biotechnology.
• The pathway is a target for antiviral and anticancer drug development due to its role in viral envelope protein maturation.
• Research on this term benefits from advanced CRISPR screening to identify novel regulatory genes.
What Happens During protein post-translational transfer of dolichol-linked oligosaccharide?
Synthesis of the dolichol-linked oligosaccharide precursor
In simple terms: The cell builds a sugar tree on a lipid carrier in the ER membrane.
The dolichol-linked oligosaccharide (LLO) precursor is assembled stepwise on the ER membrane. This involves the sequential addition of monosaccharides to dolichol phosphate, forming a Glc3Man9GlcNAc2 structure. The process is highly conserved and requires numerous glycosyltransferases.
Recognition of the Asn-X-Ser/Thr sequon
In simple terms: The OST complex scans new proteins for a specific three-amino-acid tag.
The OST complex recognizes the consensus sequence Asn-X-Ser/Thr (where X is any amino acid except proline) in the nascent polypeptide as it emerges from the translocon. This recognition is essential for the co-translational transfer of the glycan.
Transfer of the oligosaccharide to asparagine
In simple terms: The sugar tree is snipped off the lipid and attached to the protein.
The OSTB complex catalyzes the en bloc transfer of the LLO precursor to the asparagine residue within the sequon. This reaction occurs in the ER lumen and is coupled to protein translocation.
Processing of the N-linked glycan
In simple terms: The attached sugar tree is trimmed and modified to help the protein fold.
After transfer, the N-linked glycan undergoes trimming by glucosidases and mannosidases, which facilitates interaction with chaperones like calnexin and calreticulin for proper folding. Further processing in the Golgi apparatus generates complex glycans.
Key Genes Involved in GO:0180057 protein post-translational transfer of dolichol-linked oligosaccharide
The following genes encode components of the OST complex and related glycosylation machinery that are directly involved in GO:0180057.
| Gene | Major Role | Research Relevance |
|---|---|---|
| STT3A | Catalytic subunit of the OST complex | Mutations cause CDG; target for glycosylation engineering |
| STT3B | Catalytic subunit of the OSTB complex | Specifically mediates post-translational transfer; studied in CDG |
| DDOST | Accessory subunit of OST | Required for stability and function of OST |
| RPN1 | Accessory subunit of OST | Involved in substrate recognition |
| RPN2 | Accessory subunit of OST | Involved in substrate recognition |
| MAGT1 | Subunit of OST | Mutations cause immunodeficiency |
| TUSC3 | Subunit of OST | Mutations cause intellectual disability |
| ALG1 | Mannosyltransferase in LLO synthesis | Defects cause CDG-Ik |
| ALG2 | Mannosyltransferase in LLO synthesis | Defects cause CDG-Ii |
| ALG3 | Mannosyltransferase in LLO synthesis | Defects cause CDG-Id |
| ALG6 | Glucosyltransferase in LLO synthesis | Defects cause CDG-Ic |
| ALG8 | Glucosyltransferase in LLO synthesis | Defects cause CDG-Ih |
| ALG9 | Mannosyltransferase in LLO synthesis | Defects cause CDG-Ij |
| ALG10 | Glucosyltransferase in LLO synthesis | Required for efficient N-glycosylation in plants |
| ALG12 | Mannosyltransferase in LLO synthesis | Defects cause CDG-Ig |
| DOLK | Dolichol kinase | Defects cause CDG-Im |
| DPM1 | Dolichol-phosphate mannose synthase | Defects cause CDG-Ie |
| MPDU1 | Mannose-P-dolichol utilization defect 1 | Defects cause CDG-If |
How Is protein post-translational transfer of dolichol-linked oligosaccharide Regulated?
The transfer of dolichol-linked oligosaccharide is regulated by the availability of dolichyl phosphate and the membrane organization of the endoplasmic reticulum. Studies in thyroid ER showed that the synthesis of N-linked carbohydrate units is controlled by membrane organization and dolichyl phosphate availability. Additionally, the expression levels of OST subunits can influence the efficiency of glycosylation.
protein post-translational transfer of dolichol-linked oligosaccharide and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| STT3A | CDG-Ia | Knockout HEK293 cells |
| ALG6 | CDG-Ic | Patient-derived fibroblasts |
| MAGT1 | Immunodeficiency | Knockout T cells |
| ALG10 | Plant growth defects | Arabidopsis knockout |
| DOLK | CDG-Im | Induced pluripotent stem cells |
Congenital Disorders of Glycosylation (CDGs)
Mutations in genes involved in the dolichol-linked oligosaccharide transfer pathway cause a group of inherited diseases known as CDGs. These disorders often present with neurological impairment, developmental delay, and multi-organ dysfunction. For example, defects in ALG genes lead to incomplete LLO precursors and inefficient transfer to proteins.
Cancer
Altered N-glycosylation is a hallmark of cancer. Changes in the expression of OST subunits and glycosyltransferases can affect cell adhesion, migration, and immune evasion. Targeting the glycosylation machinery is being explored as a therapeutic strategy.
Immunological Disorders
Defects in the OST complex, such as mutations in MAGT1, can lead to immunodeficiency due to impaired glycosylation of immune receptors. This highlights the importance of this process in immune function.
From protein post-translational transfer of dolichol-linked oligosaccharide-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the role of STT3B in post-translational glycosylation? | STT3B knockout HEK293 cells |
| How does ALG6 mutation affect LLO structure? | ALG6 point mutation knock-in in HeLa |
| Can overexpression of OST subunits enhance glycosylation? | Overexpression of STT3A in CHO cells |
| What is the interactome of OST complex? | Tagged knock-in of DDOST in HEK293 |
| How does dolichol phosphate availability regulate transfer? | Knockout of DOLK in HepG2 |
| Does ALG10 deficiency affect plant development? | Arabidopsis alg10 mutant |
How to Study the protein post-translational transfer of dolichol-linked oligosaccharide Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Metabolic labeling | Incorporation of radioactive sugars into proteins | Pulse-chase analysis of glycosylation kinetics |
| Mass spectrometry | Glycan composition and site occupancy | Structural characterization of glycoproteins |
| CRISPR screen | Gene essentiality for glycosylation | Identification of novel regulators |
| Lectin flow cytometry | Cell surface glycan levels | Screening for glycosylation mutants |
| Western blot with glycosylation-specific antibodies | Glycosylation status of target proteins | Validation of knockout phenotypes |
| RT-qPCR | Expression of glycosylation genes | Transcriptional regulation studies |
| Immunofluorescence | Subcellular localization of OST subunits | ER localization studies |
Metabolic Labeling with Radioactive Sugars
Metabolic labeling with 3H-mannose or 14C-glucosamine followed by immunoprecipitation can measure the rate of N-glycosylation of specific proteins. This method is useful for pulse-chase experiments to track glycan transfer.
Mass Spectrometry of Glycopeptides
LC-MS/MS can identify glycosylation sites and glycan structures on target proteins, providing direct evidence of transfer. This is essential for confirming the Asn-X-Ser/Thr motif usage.
CRISPR-Cas9 Knockout Screening
Genome-wide CRISPR screens can identify genes required for efficient N-glycosylation, such as OST subunits and LLO synthesis enzymes. This approach is powerful for discovering novel regulators.
Flow Cytometry with Lectins
Lectin staining, such as with ConA or WGA, can assess cell surface glycosylation levels in live cells. This is a rapid method to screen for glycosylation defects.
How CRISPR Can Be Used to Study GO:0180057 protein post-translational transfer of dolichol-linked oligosaccharide
Knockout
CRISPR knockout of OST subunits such as STT3A or STT3B can abolish N-glycosylation, leading to protein misfolding and ER stress. These models are valuable for studying the consequences of glycosylation loss.
Point Mutation
Introducing point mutations in the catalytic domain of STT3B can dissect its enzymatic activity and substrate specificity. Such models help understand the molecular basis of CDGs.
Knock-in
Knock-in of tagged OST subunits (e.g., HA-tagged DDOST) allows for affinity purification and interactome analysis. This reveals the composition and dynamics of the OST complex.
Overexpression
Overexpression of OST subunits or LLO synthesis enzymes can enhance glycosylation capacity in biotechnological cell lines. This is used to improve therapeutic protein production.
How EDITGENE Supports protein post-translational transfer of dolichol-linked oligosaccharide Research
Researchers studying protein post-translational transfer of dolichol-linked oligosaccharide-related genes often need to determine whether a candidate gene is causally involved in glycosylation efficiency, protein folding, or disease phenotypes. EDITGENE provides comprehensive CRISPR services to generate precisely engineered cell models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for protein post-translational transfer of dolichol-linked oligosaccharide research.
Frequently Asked Questions About protein post-translational transfer of dolichol-linked oligosaccharide
What is GO:0180057?
GO:0180057 is a Gene Ontology term for the biological process of protein post-translational transfer of dolichol-linked oligosaccharide, a key step in N-linked glycosylation.
What genes are involved in protein post-translational transfer of dolichol-linked oligosaccharide?
Key genes include STT3A, STT3B, DDOST, RPN1, RPN2, MAGT1, TUSC3, and ALG family genes.
What is the role of the OSTB complex?
The OSTB complex mediates the transfer of the dolichol-linked oligosaccharide to asparagine residues in nascent proteins.
How is protein post-translational transfer of dolichol-linked oligosaccharide regulated?
It is regulated by dolichyl phosphate availability and membrane organization in the endoplasmic reticulum.
What diseases are associated with defects in this process?
Defects cause congenital disorders of glycosylation (CDGs), cancer, and immunological disorders.
What methods are used to study this process?
Methods include metabolic labeling, mass spectrometry, CRISPR screens, and lectin flow cytometry.
Can CRISPR be used to study this pathway?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are widely used.
What is the Asn-X-Ser/Thr motif?
It is the consensus sequence on target proteins where N-glycosylation occurs.
What is the dolichol-linked oligosaccharide precursor?
It is a lipid-linked sugar tree that is transferred en bloc to proteins.
How does EDITGENE support research on this term?
EDITGENE provides custom CRISPR cell models, library screening, and bioinformatics services for glycosylation research.
Conclusion
GO:0180057 represents a fundamental biological process in N-linked glycosylation, with far-reaching implications for protein function, human health, and biotechnology. Understanding its mechanism and regulation is essential for developing therapies for glycosylation disorders and improving biopharmaceutical production. EDITGENE offers a suite of CRISPR tools to facilitate this research.
References
- 1. Tsai PK et al.. 1984. Isolation of glucose-containing high-mannose glycoprotein core oligosaccharides.. Proc Natl Acad Sci U S A 81(20):6340-3 PMID: 6387703
- 2. Farid A et al.. 2011. Arabidopsis thaliana alpha1,2-glucosyltransferase (ALG10) is required for efficient N-glycosylation and leaf growth.. Plant J 68(2):314-25 PMID: 21707802
- 3. Spiro MJ et al.. 1986. Control of N-linked carbohydrate unit synthesis in thyroid endoplasmic reticulum by membrane organization and dolichyl phosphate availability.. J Biol Chem 261(31):14725-32 PMID: 2429959
