Editors' ChoiceCell Biology

Nutrient Sensing on Both Sides

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Science's STKE  16 May 2006:
Vol. 2006, Issue 335, pp. tw162
DOI: 10.1126/stke.3352006tw162

Some plasma membrane sensors that recognize nutrients, such as amino acids and sugars, structurally resemble the transporters, yet apparently lack transport function. Wu et al. provide evidence for a model in which the Saccharomyces cerevisiae amino acid sensor Ssy1 has an outward-facing conformation that binds extracellular ligands, which stimulates signaling, and an inward-facing conformation that binds intracellular ligands, which inhibits signaling. When yeast were grown under conditions that increased intracellular leucine, the dissociation constant for extracellular leucine or phenylalanine was increased, that is, higher concentrations of extracellular ligand were required to stimulate processing of the Stp1 transcription factor that is downstream of Ssy1. Based on the data, the authors present a model that predicts that the concentration ratio across the plasma membrane, not just the extracellular ligand concentration, is sensed.

B. Wu, K. Ottow, P. Poulsen, R. F. Gaber, E. Albers, M. C. Kielland-Brandt, Competitive intra- and extracellular nutrient sensing by the transporter homologue Ssy1p. J. Cell Biol. 173, 327-331 (2006). [Abstract] [Full Text]

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