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MBC in Press, published online ahead of print August 2, 2006
Mol. Biol. Cell 10.1091/mbc.E06-06-0506

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Submitted on June 8, 2006
Revised on July 19, 2006
Accepted on July 26, 2006

Activity-dependent Reversible Inactivation of the General Amino Acid Permease

April L. Risinger, Natalie E. Cain, Esther J. Chen,* and Chris A. Kaiser

Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139

Monitoring Editor: David Drubin

The general amino acid permease, Gap1p, of S. cerevisiae transports all naturally occurring amino acids into yeast cells for use as a nitrogen source. Previous studies have shown that a nonubiquitinateable form of the permease, Gap1pK9R,K16R, is constitutively localized to the plasma membrane. Here, we report that amino acid transport activity of Gap1pK9R,K16R can be rapidly and reversibly inactivated at the plasma membrane by the presence of amino acid mixtures. Surprisingly, we also find that addition of most single amino acids is lethal to Gap1pK9R,K16R expressing cells, whereas mixtures of amino acids are less toxic. This toxicity appears to be the consequence of uptake of unusually large quantities of a single amino acid. Exploiting this toxicity, we isolated gap1 alleles deficient in transport of a subset of amino acids. Using these mutations, we show that Gap1p inactivation at the plasma membrane does not depend on the presence of either extracellular or intracellular amino acids, but does require active amino acid transport by Gap1p. Together, our findings uncover a new mechanism for inhibition of permease activity in response to elevated amino acid levels and provide a physiological explanation for the stringent regulation of Gap1p activity in response to amino acids.

*Present address: Department of Biological Sciences, Stanford University, Stanford, CA 94305-5020.

Address correspondence to: Chris A. Kaiser (ckaiser{at}mit.edu)




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A. L. Risinger and C. A. Kaiser
Different Ubiquitin Signals Act at the Golgi and Plasma Membrane to Direct GAP1 Trafficking
Mol. Biol. Cell, July 1, 2008; 19(7): 2962 - 2972.
[Abstract] [Full Text] [PDF]


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