AmtB-mediated NH₃ transport in prokaryotes must be active and as a consequence regulation of transport by GlnK is mandatory to limit futile cycling of NH₄ ⁺/NH₃
2011
Boogerd, Fred C. | Ma, Hongwu | Bruggeman, Frank J. | van Heeswijk, Wally C. | García-Contreras, Rodolfo | Molenaar, Douwe | Krab, Klaas | Westerhoff, Hans V.
The nature of the ammonium import into prokaryotes has been controversial. A systems biological approach makes us hypothesize that AmtB-mediated import must be active for intracellular NH₄ ⁺ concentrations to sustain growth. Revisiting experimental evidence, we find the permeability assays reporting passive NH₃ import inconclusive. As an inevitable consequence of the proposed NH₄ ⁺ transport, outward permeation of NH₃ constitutes a futile cycle. We hypothesize that the regulatory protein GlnK is required to fine-tune the active transport of ammonium in order to limit futile cycling whilst enabling an intracellular ammonium level sufficient for the cell’s nitrogen requirements.
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