OST1/YJL002C Summary Help

Standard Name OST1 1
Systematic Name YJL002C
Alias NLT1
Feature Type ORF, Verified
Description Alpha subunit of the oligosaccharyltransferase complex of the ER lumen; complex catalyzes asparagine-linked glycosylation of newly synthesized proteins (1, 2 and see Summary Paragraph)
Name Description OligoSaccharylTransferase 1
Chromosomal Location
ChrX:434651 to 433221 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Gene Ontology Annotations All OST1 GO evidence and references
  View Computational GO annotations for OST1
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 9 genes
Classical genetics
Large-scale survey
reduction of function
167 total interaction(s) for 78 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 19
  • Affinity Capture-RNA: 2
  • Affinity Capture-Western: 23
  • Co-purification: 13
  • PCA: 20

Genetic Interactions
  • Dosage Rescue: 1
  • Negative Genetic: 84
  • Positive Genetic: 2
  • Synthetic Lethality: 3

Expression Summary
Length (a.a.) 476
Molecular Weight (Da) 54,071
Isoelectric Point (pI) 4.88
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrX:434651 to 433221 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..1431 434651..433221 2011-02-03 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 SGDIDS000003539

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.

Ost1p is the alpha subunit of the OST complex, one of the original six subunits purified (1, 6). Also known as Nlt1p, for N-linked oligosaccharyl transferase (7), Ost1p was once thought to be responsible for recognition of the glycosylation target site in proteins (8), but this function is now assigned to Stt3p (9, 10, 11).

Deletion of OST1 is lethal in haploid cells (1, 7), and temperature-sensitive (ts) mutants arrest within four generations (1). In addition to glycosylation defects, some ts mutants grow slowly and form clumps in liquid culture at the permissive temperature, possibly due to defective separation of mother and daughter cells (1).

Ost1p is homologous to mammalian ribophorin I (OMIM) (1, 7), a component of the mammalian OST complex, along with ribophorin II (OMIM) and OST48 (OMIM).

Last updated: 2005-06-27 Contact SGD

References cited on this page View Complete Literature Guide for OST1
1) Silberstein S, et al.  (1995) The alpha subunit of the Saccharomyces cerevisiae oligosaccharyltransferase complex is essential for vegetative growth of yeast and is homologous to mammalian ribophorin I. J Cell Biol 128(4):525-36
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) Kelleher DJ and Gilmore R  (1994) The Saccharomyces cerevisiae oligosaccharyltransferase is a protein complex composed of Wbp1p, Swp1p, and four additional polypeptides. J Biol Chem 269(17):12908-17
7) Pathak R, et al.  (1995) The essential yeast NLT1 gene encodes the 64 kDa glycoprotein subunit of the oligosaccharyl transferase. FEBS Lett 362(2):229-34
8) Yan Q, et al.  (1999) The Ost1p subunit of yeast oligosaccharyl transferase recognizes the peptide glycosylation site sequence, -Asn-X-Ser/Thr-. J Biol Chem 274(8):5021-5
9) Yan Q and Lennarz WJ  (2002) Studies on the function of oligosaccharyl transferase subunits. Stt3p is directly involved in the glycosylation process. J Biol Chem 277(49):47692-700
10) Yan Q and Lennarz WJ  (2002) Studies on the function of oligosaccharyl transferase subunits: a glycosylatable photoprobe binds to the luminal domain of Ost1p. Proc Natl Acad Sci U S A 99(25):15994-9
11) Nilsson I, et al.  (2003) Photocross-linking of nascent chains to the STT3 subunit of the oligosaccharyltransferase complex. J Cell Biol 161(4):715-25