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

• Protein deglycosylation with peptide-N-glycosidase F (PNGase F) indicates that, in contrast to Mep1 and Mep3, Mep2 is an asparagine-linked glycoprotein [7].

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].

References