SEC53/YFL045C Summary Help

Standard Name SEC53 1
Systematic Name YFL045C
Alias ALG4 2
Feature Type ORF, Verified
Description Phosphomannomutase; involved in synthesis of GDP-mannose and dolichol-phosphate-mannose; required for folding and glycosylation of secretory proteins in the ER lumen (3, 4 and see Summary Paragraph)
Name Description SECretory 1
Chromosomal Location
ChrVI:44392 to 43628 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Gene Ontology Annotations All SEC53 GO evidence and references
  View Computational GO annotations for SEC53
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 8 genes
Classical genetics
Large-scale survey
66 total interaction(s) for 57 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 35
  • Affinity Capture-RNA: 4
  • PCA: 1
  • Two-hybrid: 1

Genetic Interactions
  • Dosage Growth Defect: 2
  • Dosage Lethality: 1
  • Dosage Rescue: 1
  • Negative Genetic: 12
  • Positive Genetic: 9

Expression Summary
Length (a.a.) 254
Molecular Weight (Da) 29,063
Isoelectric Point (pI) 4.99
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrVI:44392 to 43628 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Last Update Coordinates: 1996-07-31 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..765 44392..43628 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 SGDIDS000001849

SEC53 was named based on its initial observed mutant phenotype that resulted in a defect early in the secretory pathway, in which cells do not properly process or transport proteins (5). SEC53 is also called ALG4, named for a defect in asparagine-linked glycosylation (2).

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 6, 7).

Sec53p is a phosphomannomutase that catalyzes the conversion of mannose-6-phosphate (Man-6-P) to mannose-1-phosphate (Man-1-P) (3) on the cytosolic surface of the endoplasmic reticulum (8). Man-1-P is subsequently converted to GDP-mannose, which is the source of some of the mannose moieties added to the growing oligosaccharide. At the restrictive temperature, sec53 mutants accumulate LLO's carrying GlcNAc and one to eight mannose moieties, but do not transfer these oligosaccharides to proteins (2). Note: Technically, the conversion of Man-6-P to Man-1-P is reversible, but the forward reaction is required for glycosylation to proceed.

Sec53p complements defective phosphomannomutase activity in Salmonella typhimurium and E. coli (3). Candida albicans PMM1 (phosphomannomutase 1) (9) and Kluyveromyces lactis SEC53 (10) complement sec53. There are two human homologs: PMM1 (11, 12) (OMIM) and PMM2 (OMIM). PMM2 deficiency causes congenital disorder of glycosylation type I-a, also known as Jaeken syndrome (OMIM).

Last updated: 2005-07-01 Contact SGD

References cited on this page View Complete Literature Guide for SEC53
1) Bernstein M, et al.  (1985) Characterization of a gene product (Sec53p) required for protein assembly in the yeast endoplasmic reticulum. J Cell Biol 101(6):2374-82
2) Huffaker TC and Robbins PW  (1983) Yeast mutants deficient in protein glycosylation. Proc Natl Acad Sci U S A 80(24):7466-70
3) Kepes F and Schekman R  (1988) The yeast SEC53 gene encodes phosphomannomutase. J Biol Chem 263(19):9155-61
4) Feldman RI, et al.  (1987) Product of SEC53 is required for folding and glycosylation of secretory proteins in the lumen of the yeast endoplasmic reticulum. J Biol Chem 262(19):9332-9
5) Ferro-Novick S, et al.  (1984) Yeast secretory mutants that block the formation of active cell surface enzymes. J Cell Biol 98(1):35-43
6) Herscovics A and Orlean P  (1993) Glycoprotein biosynthesis in yeast. FASEB J 7(6):540-50
7) Burda P and Aebi M  (1999) The dolichol pathway of N-linked glycosylation. Biochim Biophys Acta 1426(2):239-57
8) Ruohola H and Ferro-Novick S  (1987) Sec53, a protein required for an early step in secretory protein processing and transport in yeast, interacts with the cytoplasmic surface of the endoplasmic reticulum. Proc Natl Acad Sci U S A 84(23):8468-72
9) Smith DJ, et al.  (1992) The Candida albicans PMM1 gene encoding phosphomannomutase complements a Saccharomyces cerevisiae sec 53-6 mutation. Curr Genet 22(6):501-3
10) Staneva D, et al.  (2004) KlSEC53 is an essential Kluyveromyces lactis gene and is homologous with the SEC53 gene of Saccharomyces cerevisiae. Yeast 21(1):41-51
11) Hansen SH, et al.  (1997) Cloning and characterization of human phosphomannomutase, a mammalian homologue of yeast SEC53. Glycobiology 7(6):829-34
12) Matthijs G, et al.  (1997) PMM (PMM1), the human homologue of SEC53 or yeast phosphomannomutase, is localized on chromosome 22q13. Genomics 40(1):41-7