Recombinant Xenopus laevis Oligosaccharyltransferase complex subunit ostc-A (ostc-a)
Description
Introduction
Recombinant Xenopus laevis Oligosaccharyltransferase Complex Subunit Ostc-A (Ostc-A) is a protein component of the oligosaccharyltransferase (OST) complex in the African clawed frog (Xenopus laevis) . The OST complex is a multi-subunit enzyme that catalyzes N-glycosylation, a crucial post-translational modification in eukaryotes . N-glycosylation is essential for protein folding, quality control, trafficking, signal transduction, and cell-to-cell communication .
Function of the OST Complex
The OST complex transfers a glycan from a dolichol pyrophosphate donor to an asparagine residue within the Asn-X-Ser/Thr consensus motif of nascent polypeptide chains in the endoplasmic reticulum (ER) . This process occurs co-translationally, where the OST complex associates with the Sec61 complex at the translocon channel to mediate protein translocation across the ER membrane .
Subunits and Isoforms of the OST Complex
In mammalian cells, there are two distinct OST complexes, STT3A-OST and STT3B-OST, which contain either STT3A or STT3B as their catalytic subunits, along with several accessory proteins . These accessory proteins include common subunits such as RPN1, RPN2, OST48/DDOST, OST4, TMEM258, and DAD1, as well as subunits specific to either STT3A-OST (DC2/OSTC and KCP2) or STT3B-OST (TUSC3 and MAGT1) . Xenopus laevis Ostc-A is a specific component of the STT3A-containing OST complex .
Role of Ostc-A
OSTC/DC2, including Xenopus laevis Ostc-A, is specific to STT3A-OST and found only in vertebrates . While not required for the enzymatic activity of STT3A-OST, OSTC/DC2 is necessary for the association with the Sec61 channel and co-translational N-glycosylation . It has been located at the interface between STT3A and Sec61, bridging the protein-conducting channel and glycosylation machinery .
Importance of OST Subunits
The accessory subunits of the OST complex, such as OST48 and DAD1, play a significant role in stabilizing both STT3A- and STT3B-containing OST complexes . Depletion of these subunits can lead to severe reduction in OST complex formation . KCP2, another STT3A-OST-specific subunit, also influences protein N-glycosylation in a substrate-specific manner .
Disease Associations and Implications
Given the crucial roles of N-glycosylation, deficiencies in genes encoding OST subunits can result in complex genetic disorders . Furthermore, the expression of OST subunits is often altered in malignant cells, contributing to tumor cell survival and proliferation . This makes OST a potential target for cancer treatment .
Expression and Characteristics
Recombinant Xenopus laevis Oligosaccharyltransferase complex subunit ostc-A (ostc-a) can be produced in vitro using an E. coli expression system .
Table 1: OST Subunits and Their Functions
| Subunit | Function | Complex Association |
|---|---|---|
| STT3A | Catalytic subunit | STT3A-OST |
| STT3B | Catalytic subunit | STT3B-OST |
| RPN1 | Accessory protein | Both STT3A-OST and STT3B-OST |
| RPN2 | Accessory protein | Both STT3A-OST and STT3B-OST |
| OST48/DDOST | Accessory protein | Both STT3A-OST and STT3B-OST |
| OST4 | Accessory protein | Both STT3A-OST and STT3B-OST |
| TMEM258 | Accessory protein | Both STT3A-OST and STT3B-OST |
| DAD1 | Accessory protein | Both STT3A-OST and STT3B-OST |
| DC2/OSTC | Sec61 channel association | STT3A-OST |
| KCP2 | N-glycosylation influence | STT3A-OST |
| TUSC3 | Specific subunit | STT3B-OST |
| MAGT1 | Specific subunit | STT3B-OST |
Table 2: Effects of OST Subunit Depletion
| Depleted Subunit | Observed Effect |
|---|---|
| OST48 | Destabilization of both STT3A- and STT3B-containing OST complexes |
| DAD1 | Destabilization of both STT3A- and STT3B-containing OST complexes |
| KCP2 | Mobility shift of the major STT3A-containing complex |
Product Specs
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Target Background
This protein is a subunit of the oligosaccharyltransferase (OST) complex. The OST complex catalyzes the transfer of a defined glycan (Glc3Man9GlcNAc2 in eukaryotes) from the lipid carrier dolichol-pyrophosphate to an asparagine residue within an Asn-X-Ser/Thr consensus motif in nascent polypeptide chains. This is the initial step in protein N-glycosylation. N-glycosylation occurs co-translationally, and the complex interacts with the Sec61 complex at the translocon, facilitating protein translocation across the endoplasmic reticulum (ER). All subunits are essential for optimal enzyme activity.
KEGG: xla:444229
UniGene: Xl.53498
