The world's first wiki where authorship really matters (Nature Genetics, 2008). Due credit and reputation for authors. Imagine a global collaborative knowledge base for original thoughts. Search thousands of articles and collaborate with scientists around the globe.

wikigene or wiki gene protein drug chemical gene disease author authorship tracking collaborative publishing evolutionary knowledge reputation system wiki2.0 global collaboration genes proteins drugs chemicals diseases compound
Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)



Gene Review

MEP1  -  ammonium permease MEP1

Saccharomyces cerevisiae S288c

Synonyms: AMT1, Ammonium transporter MEP1, G6331, YGR121C
Welcome! If you are familiar with the subject of this article, you can contribute to this open access knowledge base by deleting incorrect information, restructuring or completely rewriting any text. Read more.

Disease relevance of MEP1

  • The predicted Mep1p protein shares high sequence similarity with several bacterial proteins of unknown function, notably the product of the nitrogen-regulated nrgA gene of Bacillus subtilis, and with that of a partial cDNA sequence derived from Caenorhabditis elegans [1].

High impact information on MEP1

  • Analysis of MEP1/MEP2 hybrid proteins identified a small intracellular loop of MEP2 involved in the pseudohyphal regulatory function [2].
  • In contrast, MEP1 and MEP3, which are lower affinity ammonium permeases, are not required for filamentous growth [2].
  • The MEP1 gene is most highly expressed when the cells are grown on low concentrations of ammonium or on 'poor' nitrogen sources like urea or proline [1].
  • In contrast, expression of either MEP1 or MEP3 requires only Gln3p and is unexpectedly down-regulated in a Nil1p-dependent manner [3].
  • We recently reported the first characterization of an NH4+ transport protein (Mep1p) in Saccharomyces cerevisiae [3].

Biological context of MEP1

  • An 18.3 kb DNA segment from yeast Saccharomyces cerevisiae VII encompasses the previously characterized MEP1, NUP57 and PPT1 genes as well as seven new open reading frames (ORFs) of at least 100 residues [4].
  • We also show that Mep permease involvement in PKA control is different from their role in haploid invasive growth, in which Mep1 sustains and Mep2 inhibits, in a way independent of the ammonium level in the medium [5].
  • We show here that, in the 26972c mutant defective in NH4+ transport, the Mep1 protein carrying an amino acid substitution in its cytoplasmic C-terminus trans-inhibits the closely related Mep3 protein [6].
  • Saccharomyces cerevisiae possesses three related ammonium transporters, Mep1, Mep2 and Mep3, differing in their kinetic properties and in the level and regulation of their gene expression [7].

Anatomical context of MEP1

  • In Saccharomyces cerevisiae, the transport of ammonium across the plasma membrane for use as a nitrogen source is mediated by at least two functionally distinct transport systems whose respective encoding genes are called MEP1 and MEP2 [1].
  • Ammonium uptake in the yeast Saccharomyces cerevisiae involves three membrane transporters (Mep1, -2 and -3) belonging to an evolutionarily conserved protein family that also includes the rhesus (Rh) blood group polypeptides of erythrocytes [6].

Associations of MEP1 with chemical compounds


Other interactions of MEP1

  • On a poor nitrogen source, MEP2 expression is much higher than MEP1 and MEP3 expression [3].
  • Here we describe the characterization of two additional NH4+ transporters, Mep2p and Mep3p, both of which are highly similar to Mep1p [3].


  1. Cloning and expression of the MEP1 gene encoding an ammonium transporter in Saccharomyces cerevisiae. Marini, A.M., Vissers, S., Urrestarazu, A., André, B. EMBO J. (1994) [Pubmed]
  2. The MEP2 ammonium permease regulates pseudohyphal differentiation in Saccharomyces cerevisiae. Lorenz, M.C., Heitman, J. EMBO J. (1998) [Pubmed]
  3. A family of ammonium transporters in Saccharomyces cerevisiae. Marini, A.M., Soussi-Boudekou, S., Vissers, S., Andre, B. Mol. Cell. Biol. (1997) [Pubmed]
  4. An 18.3 kb DNA fragment from yeast chromosome VII carries four unknown open reading frames, the gene for an Asn synthase, remnants of Ty and three tRNA genes. Van Dyck, L., Tettelin, H., Purnelle, B., Goffeau, A. Yeast (1997) [Pubmed]
  5. Ammonium permease-based sensing mechanism for rapid ammonium activation of the protein kinase A pathway in yeast. Van Nuland, A., Vandormael, P., Donaton, M., Alenquer, M., Lourenço, A., Quintino, E., Versele, M., Thevelein, J.M. Mol. Microbiol. (2006) [Pubmed]
  6. Cross-talk between ammonium transporters in yeast and interference by the soybean SAT1 protein. Marini, A.M., Springael, J.Y., Frommer, W.B., André, B. Mol. Microbiol. (2000) [Pubmed]
  7. In vivo N-glycosylation of the mep2 high-affinity ammonium transporter of Saccharomyces cerevisiae reveals an extracytosolic N-terminus. Marini, A.M., André, B. Mol. Microbiol. (2000) [Pubmed]
WikiGenes - Universities