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PMID:12455974

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Citation

Monahan, BJ, Fraser, JA, Hynes, MJ and Davis, MA (2002) Isolation and characterization of two ammonium permease genes, meaA and mepA, from Aspergillus nidulans. Eukaryotic Cell 1:85-94

Abstract

Ammonium and the analogue methylammonium are taken into the cell by active transport systems which constitute a family of transmembrane proteins that have been identified in fungi, bacteria, plants, and animals. Two genes from Aspergillus nidulans, mepA and meaA, which encode ammonium transporters with different affinities have been characterized. The MepA transporter exhibits the highest affinity for methylammonium (Km, 44.3 microM); in comparison, the Km for MeaA is 3.04 mM. By use of targeted gene replacement strategies, meaA and mepA deletion mutants were created. Deletion of both meaA and mepA resulted in the inability of the strain to grow on ammonium concentrations of less than 10 mM. The single meaA deletion mutant exhibited reduced growth at the same concentrations, whereas the mepA deletion mutant displayed wild-type growth. Interestingly, multiple copies of mepA were found to complement the methylammonium resistance phenotype conferred by the deletion of meaA. The expression profiles for mepA and meaA differed; the mepA transcript was detected only in nitrogen-starved cultures, whereas meaA was expressed under both ammonium-sufficient and nitrogen starvation conditions. Together, these results indicate that MeaA constitutes the major ammonium transport activity and is required for the optimal growth of A. nidulans on ammonium as the sole nitrogen source and that MepA probably functions in scavenging low concentrations of ammonium under nitrogen starvation conditions.

Links

PubMed PMC118046

Keywords

Animals; Aspergillus nidulans/genetics; Aspergillus nidulans/growth & development; Aspergillus nidulans/metabolism; Biological Transport, Active; Cation Transport Proteins; Fungal Proteins/genetics; Gene Deletion; Humans; Kinetics; Membrane Transport Proteins/genetics; Methylamines/pharmacokinetics; Phylogeny; Restriction Mapping

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

EMENI:G5EB09

acts_upstream_of_or_within

GO:0019740: nitrogen utilization

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

EMENI:G5EB09

acts_upstream_of_or_within

GO:0015696: ammonium transport

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

EMENI:G5EB09

enables

GO:0008519: ammonium transmembrane transporter activity

ECO:0000314: direct assay evidence used in manual assertion

F

Seeded From UniProt

complete

EMENI:G5EB13

acts_upstream_of_or_within

GO:0019740: nitrogen utilization

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

EMENI:G5EB13

acts_upstream_of_or_within

GO:0015696: ammonium transport

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

EMENI:G5EB13

enables

GO:0008519: ammonium transmembrane transporter activity

ECO:0000314: direct assay evidence used in manual assertion

F

Seeded From UniProt

complete

EMEND:Q8TFN9

GO:0015200: methylammonium transmembrane transporter activity

ECO:0000315:

F

Figure 4C shows that meaA deletion mutants take up less methylammonium at 1mM final methylammonium concentration than wildtype A. nidulans suggesting meaA functions as an ammonium transporter.

complete
CACAO 8056

EMEND:Q8TFN9

enables

GO:0015200: methylammonium transmembrane transporter activity

ECO:0000315: mutant phenotype evidence used in manual assertion

F

Seeded From UniProt

complete

EMEND:Q8TFN8

GO:0015200: methylammonium transmembrane transporter activity

ECO:0000315:

F

Figure 4C shows that mepA deletion mutants take up methylammonium at a lower rate than wildtype A. nidulans cells suggesting mepA's role as an ammonium transporter.

complete
CACAO 8057

EMEND:Q8TFN8

enables

GO:0015200: methylammonium transmembrane transporter activity

ECO:0000315: mutant phenotype evidence used in manual assertion

F

Seeded From UniProt

complete


See also

References

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