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

MEP2  -  ammonium permease MEP2

Saccharomyces cerevisiae S288c

Synonyms: AMT2, Ammonium transporter MEP2, N1207, N1820, YNL142W
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.

High impact information on MEP2

  • Analysis of MEP1/MEP2 hybrid proteins identified a small intracellular loop of MEP2 involved in the pseudohyphal regulatory function [1].
  • High-level MEP2 transcription requires at least one of the two GATA family factors Gln3p and Nil1p, which are involved in transcriptional activation of many other nitrogen-regulated genes [2].
  • Npr1 is a kinase that phosphorylates and thereby stabilizes NCR-sensitive permeases, e.g. Gap1 and Mep2 [3].
  • The non-metabolizable ammonium analogue, methylamine, also triggers activation of trehalase when transported by Mep2 but not when taken up by diffusion [4].
  • Mutagenesis of Asn246 to Ala in Mep2 abolished transport and signalling with methylamine but had no effect with ammonium [4].

Biological context of MEP2

  • Mep2 glycosylation is not required for pseudohyphal differentiation in response to ammonium starvation, and its absence causes only a slight reduction in the affinity of the transporter for its substrate [5].
  • Also, the importance of a putative site for phosphorylation by protein kinase A was investigated in both Mep2p and Ump2p via site-directed mutagenesis of the respective genes [6].
  • 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 [4].
  • Specific point mutations in Mep2 uncouple signalling from transport [7].

Anatomical context of MEP2

  • 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 [8].
  • Consistently, treatment of intact protoplasts with proteinase K leads to specific proteolysis of the N-terminal tail of Mep2 [5].
  • In yeast Mep2, replacement of aspartate(186) with asparagine produced an inactive transporter localized at the cell surface, whilst replacement with alanine was accompanied by stacking of the protein in the endoplasmic reticulum [9].

Associations of MEP2 with chemical compounds

  • Here we describe the characterization of two additional NH4+ transporters, Mep2p and Mep3p, both of which are highly similar to Mep1p [2].
  • A carboxyl group at position 186 of Mep2 therefore appears mandatory for function [9].
  • Here, we show that the analogous aspartate residue is critical for the transport function of eukaryotic family members as distant as the yeast transporter/sensor Mep2 and the human RhAG and RhCG proteins [9].

Regulatory relationships of MEP2

  • Our data also reveal that the requirement of Npr1 for ammonium-induced pseudohyphal growth is an indirect consequence of its necessity for Mep2-mediated ammonium transport [10].

Other interactions of MEP2

  • Recognition of nitrogen starvation is mediated, at least in part, by the ammonium permease Mep2p and the Galpha subunit Gpa2p [11].
  • Strikingly, the transmembrane components of several of these sensors, Ssylp, Mep2p, Snf3p. and Rgt2p, are unique members of nutrient-transport protein families [12].

Analytical, diagnostic and therapeutic context of MEP2

  • Site-directed mutagenesis of the four potential N-glycosylation sites of Mep2 shows that Asn-4 of the protein's N-terminal tail is the only site that binds oligosaccharides [5].


  1. The MEP2 ammonium permease regulates pseudohyphal differentiation in Saccharomyces cerevisiae. Lorenz, M.C., Heitman, J. EMBO J. (1998) [Pubmed]
  2. A family of ammonium transporters in Saccharomyces cerevisiae. Marini, A.M., Soussi-Boudekou, S., Vissers, S., Andre, B. Mol. Cell. Biol. (1997) [Pubmed]
  3. Ammonia-specific Regulation of Gln3 Localization in Saccharomyces cerevisiae by Protein Kinase Npr1. Tate, J.J., Rai, R., Cooper, T.G. J. Biol. Chem. (2006) [Pubmed]
  4. 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]
  5. 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]
  6. Isolation and characterization from pathogenic fungi of genes encoding ammonium permeases and their roles in dimorphism. Smith, D.G., Garcia-Pedrajas, M.D., Gold, S.E., Perlin, M.H. Mol. Microbiol. (2003) [Pubmed]
  7. Nutrient sensing systems for rapid activation of the protein kinase A pathway in yeast. Thevelein, J.M., Geladé, R., Holsbeeks, I., Lagatie, O., Popova, Y., Rolland, F., Stolz, F., Van de Velde, S., Van Dijck, P., Vandormael, P., Van Nuland, A., Van Roey, K., Van Zeebroeck, G., Yan, B. Biochem. Soc. Trans. (2005) [Pubmed]
  8. 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]
  9. Structural involvement in substrate recognition of an essential aspartate residue conserved in Mep/Amt and Rh-type ammonium transporters. Marini, A.M., Boeckstaens, M., Benjelloun, F., Chérif-Zahar, B., André, B. Curr. Genet. (2006) [Pubmed]
  10. The yeast ammonium transport protein Mep2 and its positive regulator, the Npr1 kinase, play an important role in normal and pseudohyphal growth on various nitrogen media through retrieval of excreted ammonium. Boeckstaens, M., André, B., Marini, A.M. Mol. Microbiol. (2007) [Pubmed]
  11. Regulators of pseudohyphal differentiation in Saccharomyces cerevisiae identified through multicopy suppressor analysis in ammonium permease mutant strains. Lorenz, M.C., Heitman, J. Genetics (1998) [Pubmed]
  12. Sensors of extracellular nutrients in Saccharomyces cerevisiae. Forsberg, H., Ljungdahl, P.O. Curr. Genet. (2001) [Pubmed]
WikiGenes - Universities