Eukaryotic Cell
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Monahan, B. J.
Right arrow Articles by Davis, M. A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Monahan, B. J.
Right arrow Articles by Davis, M. A.

 Previous Article  |  Next Article 

Eukaryotic Cell, February 2002, p. 85-94, Vol. 1, No. 1
1535-9778/02/$04.00+0     DOI: 10.1128/EC.1.1.85-94.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Isolation and Characterization of Two Ammonium Permease Genes, meaA and mepA, from Aspergillus nidulans

*** Brendon J. Monahan, James A. Fraser, Michael J. Hynes,* and Meryl A. Davis

Department of Genetics, University of Melbourne, Parkville, Victoria, Australia 3010

Received 9 August 2001/ Accepted 19 September 2001

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 (Km0, 44.3 µM); 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.

* Corresponding author. Mailing address: Department of Genetics, University of Melbourne, Parkville, Victoria, Australia 3010. Phone: (61) (3) 8344 5140. Fax: (61) (3) 8344 5139. E-mail: mjhynes{at}unimelb.edu.au.

Eukaryotic Cell, February 2002, p. 85-94, Vol. 1, No. 1
1535-9778/02/$04.00+0     DOI: 10.1128/EC.1.1.85-94.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:



HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Appl. Environ. Microbiol. Infect. Immun. J. Bacteriol.
Mol. Cell Biol. Microbiol. Mol. Biol. Rev. ALL ASM JOURNALS
Copyright © 2002 by the American Society for Microbiology.