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Membrane potential independent transport of NH3 in the absence of ammonium permeases in Saccharomyces cerevisiae
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2017 (English)In: BMC Systems Biology, ISSN 1752-0509, E-ISSN 1752-0509, Vol. 11, 49Article in journal (Refereed) Published
Abstract [en]

Background: Microbial production of nitrogen containing compounds requires a high uptake flux and assimilation of the N-source (commonly ammonium), which is generally coupled with ATP consumption and negatively influences the product yield. In the industrial workhorse Saccharomyces cerevisiae, ammonium (NH4+) uptake is facilitated by ammonium permeases (Mep1, Mep2 and Mep3), which transport the NH4+ ion, resulting in ATP expenditure to maintain the intracellular charge balance and pH by proton export using the plasma membrane-bound H+ -ATPase. Results: To decrease the ATP costs for nitrogen assimilation, the Mep genes were removed, resulting in a strain unable to uptake the NH4+ ion. Subsequent analysis revealed that growth of this Delta mep strain was dependent on the extracellular NH3 concentrations. Metabolomic analysis revealed a significantly higher intracellular NHX concentration (3.3-fold) in the Delta mep strain than in the reference strain. Further proteomic analysis revealed significant up-regulation of vacuolar proteases and genes involved in various stress responses. Conclusions: Our results suggest that the uncharged species, NH3, is able to diffuse into the cell. The measured intracellular/extracellular NHX ratios under aerobic nitrogen-limiting conditions were consistent with this hypothesis when NHx compartmentalization was considered. On the other hand, proteomic analysis indicated a more pronounced N-starvation stress response in the Delta mep strain than in the reference strain, which suggests that the lower biomass yield of the Delta mep strain was related to higher turnover rates of biomass components.

Place, publisher, year, edition, pages
BIOMED CENTRAL LTD , 2017. Vol. 11, 49
Keyword [en]
Intracellular ammonium, Metabolomics, Ammonium transport, Central nitrogen metabolism, Ammonia passive diffusion, Thermodynamics
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:kth:diva-207684DOI: 10.1186/s12918-016-0381-1ISI: 000399708500001PubMedID: 28412970Scopus ID: 2-s2.0-85018464439OAI: oai:DiVA.org:kth-207684DiVA: diva2:1104660
Note

QC 20170601

Available from: 2017-06-01 Created: 2017-06-01 Last updated: 2017-06-01Bibliographically approved

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van Maris, Antonius J. A.
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CiteExportLink to record
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  • apa
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