PSA1/YDL055C Summary Help

Standard Name PSA1 1
Systematic Name YDL055C
Alias MPG1 , VIG9 , SRB1
Feature Type ORF, Verified
Description GDP-mannose pyrophosphorylase (mannose-1-phosphate guanyltransferase); synthesizes GDP-mannose from GTP and mannose-1-phosphate in cell wall biosynthesis; required for normal cell wall structure (2, 3 and see Summary Paragraph)
Chromosomal Location
ChrIV:356759 to 355674 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Gene Ontology Annotations All PSA1 GO evidence and references
  View Computational GO annotations for PSA1
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Regulators 9 genes
Classical genetics
reduction of function
Large-scale survey
reduction of function
143 total interaction(s) for 121 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 103
  • Affinity Capture-RNA: 5
  • PCA: 9
  • Two-hybrid: 2

Genetic Interactions
  • Dosage Rescue: 4
  • Negative Genetic: 11
  • Phenotypic Enhancement: 1
  • Positive Genetic: 8

Expression Summary
Length (a.a.) 361
Molecular Weight (Da) 39,566
Isoelectric Point (pI) 6.29
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrIV:356759 to 355674 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Last Update Coordinates: 2004-02-11 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..1086 356759..355674 2004-02-11 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 SGDIDS000002213

PSA1 encodes GDP-Man pyrophosphorylase (EC (2, 4), which synthesizes GDP-mannose from mannose-1-phosphate and GTP. This is a necessary step in the preparation of mannose for incorporation into N-linked and O-linked glycoproteins, and psa1 mutants exhibit defects in both processes (2). In this pathway, Psa1p lies downstream of Sec53p and upstream of Dpm1p. Deletion of PSA1 is lethal (2, 5), but hypomorphic mutants exhibit a variety of phenotypes indicating a defect in cell wall biosynthesis. Specifically, psa1 mutants are sensitive to hypoosmolarity and require sorbitol in their growth medium (3); they are also unable to mate (3), hypersensitive to the drug geneticin (G418) (2), inefficiently transformed by electroporation or lithium acetate (3), and they leak cell surface proteins into the surrounding medium (3).

PSA1 was cloned as a multicopy suppressor (plasmid suppressor of alg1) that partially restored viability to an alg1 mutant strain in a cln1 cln2 background (5). PSA1 expression appears to be cell-cycle regulated, with transcription patterns similar to those of CLN2 and increasing 4-6x near the start of the cell cycle (5). PSA1 has been independently identified in several mutant screens and thus has multiple aliases, including VIG9 (vanadate-resistant and immature glycosylation) (2), SRB1 (requires sorbitol) (3, 6), and MPG1 (mannose-1-phosphate guanyltransferase) (4). The null phenotype is complemented by introduction of the Candida albicans (7, 8), Candida glabrata (8), or Kluyveromyces lactis (9) homologs.

Last updated: 2005-07-01 Contact SGD

References cited on this page View Complete Literature Guide for PSA1
1) Schultz, J. and G.F. Sprague  (1995) Isolation of the gene encoding mannose-1-phosphate guanyltransferase from yeast. Unpublished
2) Hashimoto H, et al.  (1997) Saccharomyces cerevisiae VIG9 encodes GDP-mannose pyrophosphorylase, which is essential for protein glycosylation. J Biol Chem 272(26):16308-14
3) Yoda K, et al.  (2000) Defect in cell wall integrity of the yeast saccharomyces cerevisiae caused by a mutation of the GDP-mannose pyrophosphorylase gene VIG9. Biosci Biotechnol Biochem 64(9):1937-41
4) Kruszewska JS, et al.  (1998) Isolation of a Trichoderma reesei cDNA encoding GTP: a-D-mannose-1-phosphate guanyltransferase involved in early steps of protein glycosylation. Curr Genet 33(6):445-50
5) Benton BK, et al.  (1996) Over-expression of S. cerevisiae G1 cyclins restores the viability of alg1 N-glycosylation mutants. Curr Genet 29(2):106-13
6) Stateva LI, et al.  (1991) Cloning and characterization of a gene which determines osmotic stability in Saccharomyces cerevisiae. Mol Cell Biol 11(8):4235-43
7) Warit S, et al.  (1998) Cloning and sequencing of the Candida albicans homologue of SRB1/PSA1/VIG9, the essential gene encoding GDP-mannose pyrophosphorylase in Saccharomyces cerevisiae. Microbiology 144 ( Pt 9)():2417-26
8) Ohta A, et al.  (2000) The VIG9 gene products from the human pathogenic fungi Candida albicans and Candida glabrata encode GDP-mannose pyrophosphorylase. Biochim Biophys Acta 1475(3):265-72
9) Uccelletti D, et al.  (2005) Enhanced secretion of heterologous proteins in Kluyveromyces lactis by overexpression of the GDP-mannose pyrophosphorylase, KlPsa1p. FEMS Yeast Res 5(8):735-46