MNS1/YJR131W Summary Help

Standard Name MNS1 1
Systematic Name YJR131W
Feature Type ORF, Verified
Description Alpha-1,2-mannosidase; involved in ER-associated protein degradation (ERAD); catalyzes the removal of one mannose residue from a glycosylated protein, converting the modification from Man9GlcNAc to Man8GlcNAc; catalyzes the last step in glycoprotein maturation in the ER and is critical for ER protein degradation (1, 2, 3, 4 and see Summary Paragraph)
Chromosomal Location
ChrX:667644 to 669293 | ORF Map | GBrowse
Gene Ontology Annotations All MNS1 GO evidence and references
  View Computational GO annotations for MNS1
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 3 genes
Classical genetics
Large-scale survey
44 total interaction(s) for 35 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 3
  • Affinity Capture-RNA: 1
  • PCA: 4
  • Two-hybrid: 2

Genetic Interactions
  • Dosage Growth Defect: 1
  • Negative Genetic: 17
  • Phenotypic Enhancement: 2
  • Phenotypic Suppression: 2
  • Positive Genetic: 10
  • Synthetic Growth Defect: 2

Expression Summary
Length (a.a.) 549
Molecular Weight (Da) 63,057
Isoelectric Point (pI) 5.52
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrX:667644 to 669293 | ORF Map | GBrowse
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..1650 667644..669293 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 SGDIDS000003892

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 5, 6).

MNS1 encodes mannosidase I (EC, which removes one of the mannose residues added by Alg9p from N-linked core oligosaccharides (1, 7). This is the last trimming reaction that occurs in the ER before maturing proteins migrate to the Golgi apparatus. At this point, improperly folded proteins are targeted for degradation in the cytoplasm by the 26S proteasome via Mnl1p and the Sec61p pore complex (3, 4, 8, 9); mutations in MNS1 cause defects in this degradation. Although MNS1p is a type II ER membrane protein (2, 10), it lacks ER retention signals and requires Rer1p for proper localization to the ER (11). The human homolog of Mns1p is called MAN1B1 (OMIM) (12, 13).

Last updated: 2005-07-12 Contact SGD

References cited on this page View Complete Literature Guide for MNS1
1) Camirand A, et al.  (1991) Glycoprotein biosynthesis in Saccharomyces cerevisiae. Isolation and characterization of the gene encoding a specific processing alpha-mannosidase. J Biol Chem 266(23):15120-7
2) Burke J, et al.  (1996) The Saccharomyces cerevisiae processing alpha 1,2-mannosidase is localized in the endoplasmic reticulum, independently of known retrieval motifs. Eur J Cell Biol 70(4):298-305
3) Knop M, et al.  (1996) N-Glycosylation affects endoplasmic reticulum degradation of a mutated derivative of carboxypeptidase yscY in yeast. Yeast 12(12):1229-38
4) Jakob CA, et al.  (1998) Degradation of misfolded endoplasmic reticulum glycoproteins in Saccharomyces cerevisiae is determined by a specific oligosaccharide structure. J Cell Biol 142(5):1223-33
5) Herscovics A and Orlean P  (1993) Glycoprotein biosynthesis in yeast. FASEB J 7(6):540-50
6) Burda P and Aebi M  (1999) The dolichol pathway of N-linked glycosylation. Biochim Biophys Acta 1426(2):239-57
7) Jelinek-Kelly S and Herscovics A  (1988) Glycoprotein biosynthesis in Saccharomyces cerevisiae. Purification of the alpha-mannosidase which removes one specific mannose residue from Man9GlcNAc. J Biol Chem 263(29):14757-63
8) Cabral CM, et al.  (2001) Dissecting glycoprotein quality control in the secretory pathway. Trends Biochem Sci 26(10):619-24
9) Kostova Z and Wolf DH  (2003) For whom the bell tolls: protein quality control of the endoplasmic reticulum and the ubiquitin-proteasome connection. EMBO J 22(10):2309-17
10) Grondin B and Herscovics A  (1992) Topology of ER processing alpha-mannosidase of Saccharomyces cerevisiae. Glycobiology 2(4):369-72
11) Massaad MJ, et al.  (1999) The processing alpha1,2-mannosidase of Saccharomyces cerevisiae depends on Rer1p for its localization in the endoplasmic reticulum. Eur J Cell Biol 78(7):435-40
12) Gonzalez DS, et al.  (1999) Identification, expression, and characterization of a cDNA encoding human endoplasmic reticulum mannosidase I, the enzyme that catalyzes the first mannose trimming step in mammalian Asn-linked oligosaccharide biosynthesis. J Biol Chem 274(30):21375-86
13) Tremblay LO and Herscovics A  (1999) Cloning and expression of a specific human alpha 1,2-mannosidase that trims Man9GlcNAc2 to Man8GlcNAc2 isomer B during N-glycan biosynthesis. Glycobiology 9(10):1073-8