OST6/YML019W Summary Help

Standard Name OST6 1
Systematic Name YML019W
Feature Type ORF, Verified
Description Subunit of the oligosaccharyltransferase complex of the ER lumen; complex catalyzes asparagine-linked glycosylation of newly synthesized proteins; similar to and partially functionally redundant with Ost3p (1, 2 and see Summary Paragraph)
Name Description OligoSaccharylTransferase 1
Chromosomal Location
ChrXIII:233457 to 234455 | ORF Map | GBrowse
Gene Ontology Annotations All OST6 GO evidence and references
  View Computational GO annotations for OST6
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Classical genetics
Large-scale survey
184 total interaction(s) for 87 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 3
  • Affinity Capture-Western: 21
  • Co-purification: 8
  • PCA: 11

Genetic Interactions
  • Dosage Rescue: 1
  • Negative Genetic: 128
  • Phenotypic Enhancement: 1
  • Positive Genetic: 8
  • Synthetic Growth Defect: 2
  • Synthetic Lethality: 1

Expression Summary
Length (a.a.) 332
Molecular Weight (Da) 37,890
Isoelectric Point (pI) 8.53
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrXIII:233457 to 234455 | ORF Map | GBrowse
Last Update Coordinates: 1996-07-31 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..999 233457..234455 1996-07-31 1996-07-31
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | E.C. | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000004481

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 (reviewed in 3, 4).

The oligosaccharyl transferase complex (OST complex) (EC transfers 14-sugar branched oligosaccharides from dolichyl pyrophosphate to asparagine residues. 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 (5) involved in protein import into the ER.

The ninth component of the OST complex isolated, Ost6p was identified as a previously uncharacterized open reading frame (ORF) homologous to Ost3p (1). Ost6p was probably not identified in earlier purifications of the OST complex because it is present at substoichiometric levels and migrates very close to Swp1p (1).

Ost3p is homologous to Ost6p (1), and several lines of evidence indicate that they are alternative members of the OST complex. Both proteins are present in the complex at substoichiometric levels. They interact with the same subset of OST complex proteins, and are not co-immunoprecipitated (6). Disruption of either OST3 or OST6 causes only a minor defect in N-glycosylation (7), but deletion of both causes severe underglycosylation of soluble and membrane-bound glycoproteins and a defect in OST complex formation, although this does not result in a growth defect (1).

Although Ost3p and Ost6p share low sequence identity, they have very similar hydropathy profiles (1). They are homologous to the human tumor suppressor N33 (OMIM) (1). One difference between them: ost6 mutants are sensitive to caffeine, SDS, and Calcofluor White--indicating a possible defect in cell wall biogenesis--while ost3 mutants are not (1).

Last updated: 2005-06-17 Contact SGD

References cited on this page View Complete Literature Guide for OST6
1) Knauer R and Lehle L  (1999) The oligosaccharyltransferase complex from Saccharomyces cerevisiae. Isolation of the OST6 gene, its synthetic interaction with OST3, and analysis of the native complex. J Biol Chem 274(24):17249-56
2) Knauer R and Lehle L  (1999) The oligosaccharyltransferase complex from yeast. Biochim Biophys Acta 1426(2):259-73
3) Herscovics A and Orlean P  (1993) Glycoprotein biosynthesis in yeast. FASEB J 7(6):540-50
4) Burda P and Aebi M  (1999) The dolichol pathway of N-linked glycosylation. Biochim Biophys Acta 1426(2):239-57
5) Chavan MM, et al.  (2005) Subunits of the translocon interact with components of the oligosaccharyl transferase complex. J Biol Chem 280(24):22917-24
6) Yan A, et al.  (2003) New findings on interactions among the yeast oligosaccharyl transferase subunits using a chemical cross-linker. J Biol Chem 278(35):33078-87
7) Karaoglu D, et al.  (1995) Functional characterization of Ost3p. Loss of the 34-kD subunit of the Saccharomyces cerevisiae oligosaccharyltransferase results in biased underglycosylation of acceptor substrates. J Cell Biol 130(3):567-77