Summary: OST3 / OST6 family
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OST3 / OST6 family Provide feedback
The proteins in this family are part of a complex of eight ER proteins that transfers core oligosaccharide from dolichol carrier to Asn-X-Ser/Thr motifs . This family includes both OST3 and OST6, each of which contains four predicted transmembrane helices. Disruption of OST3 and OST6 leads to a defect in the assembly of the complex. Hence, the function of these genes seems to be essential for recruiting a fully active complex necessary for efficient N-glycosylation .
Karaoglu D, Kelleher DJ, Gilmore R; , J Cell Biol 1995;130:567-577.: Functional characterization of Ost3p. Loss of the 34-kD subunit of the Saccharomyces cerevisiae oligosaccharyltransferase results in biased underglycosylation of acceptor substrates. PUBMED:7622558 EPMC:7622558
Knauer R, Lehle L; , J Biol Chem 1999;274:17249-17256.: The oligosaccharyltransferase complex from Saccharomyces cerevisiae. Isolation of the OST6 gene, its synthetic interaction with OST3, and analysis of the native complex. PUBMED:10358084 EPMC:10358084
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR021149
During N-linked glycosylation of proteins, oligosaccharide chains are assembled on the carrier molecule dolichyl pyrophosphate in the following order: 2 molecules of N-acetylglucosamine (GlcNAc), 9 molecules of mannose, and 3 molecules of glucose. These 14-residue oligosaccharide cores are then transferred to asparagine residues on nascent polypeptide chains in the endoplasmic reticulum (ER). As proteins progress through the Golgi apparatus, the oligosaccharide cores are modified by trimming and extension to generate a diverse array of glycosylated proteins [PUBMED:8472892, PUBMED:9878760].
The oligosaccharyl transferase complex (OST complex) EC transfers 14-sugar branched oligosaccharides from dolichyl pyrophosphate to asparagine residues [PUBMED:7622558]. The complex contains nine protein subunits: Ost1p, Ost2p, Ost3p, Ost4p, Ost5p, Ost6p, Stt3p, Swp1p, and Wbp1p, all of which are integral membrane proteins of the ER. The OST complex interacts with the Sec61p pore complex [PUBMED:15831493] involved in protein import into the ER.
This entry represents subunits OST3 and OST6. OST3 is homologous to OST6 [PUBMED:10358084], and several lines of evidence indicate that they are alternative members of the OST complex. Disruption of both OST3 and OST6 causes severe underglycosylation of soluble and membrane-bound glycoproteins and a defect in the assembly of the complex. Hence, the function of these genes seems to be essential for recruiting a fully active complex necessary for efficient N-glycosylation [PUBMED:10358084]. This entry also includes the magnesium transporter protein 1, also known as OST3 homologue B, which might be involved in N-glycosylation through its association with the oligosaccharyl transferase (OST) complex.
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This clan contains families related to the thioredoxin family. Thioredoxins are small enzymes that are involved in redox reactions via the reversible oxidation of an active centre disulfide bond. The thioredoxin fold consists of a 3 layer alpha/beta/alpha sandwich and a central beta sheet.
The clan contains the following 45 members:2Fe-2S_thioredx AhpC-TSA AhpC-TSA_2 ArsC ArsD Calsequestrin DIM1 DSBA DUF1525 DUF1687 DUF2703 DUF4174 DUF836 DUF899 DUF953 ERp29_N Glutaredoxin GSHPx GST_N GST_N_2 GST_N_3 HyaE KaiB MRP-S23 MRP-S25 OST3_OST6 Phosducin Redoxin SCO1-SenC SelP_N SH3BGR T4_deiodinase Thioredox_DsbH Thioredoxin Thioredoxin_2 Thioredoxin_3 Thioredoxin_4 Thioredoxin_5 Thioredoxin_6 Thioredoxin_7 Thioredoxin_8 Thioredoxin_9 Tom37 TraF YtfJ_HI0045
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Curation and family details
|Seed source:||Wood V|
|Author:||Wood V, Bateman A|
|Number in seed:||19|
|Number in full:||672|
|Average length of the domain:||142.80 aa|
|Average identity of full alignment:||26 %|
|Average coverage of the sequence by the domain:||50.64 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||8|
|Download:||download the raw HMM for this family|
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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the OST3_OST6 domain has been found. There are 3 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.
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