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Published on: January 10, 2018
Amino acid sensing by Ssy1
1Carlsberg Laboratory, Gamle Carlsberg Vej 10, DK-2500 Copenhagen Valby, Denmark.
Biochemical Society Transactions
|January 26, 2005
Summary
Saccharomyces cerevisiae senses amino acids using Ssy1, a protein that doesn't transport them. Gain-of-function mutations in SSY1 reveal sensing occurs independently of transport, likely via direct amino acid interaction.
Area of Science:
- Molecular and Cellular Biology
- Yeast Genetics
- Signal Transduction
Background:
- Saccharomyces cerevisiae utilizes Gap1 and Ssy1 for sensing extracellular amino acids.
- Ssy1, despite structural similarity to transporters, does not facilitate amino acid transport.
- Amino acid sensing by Ssy1 triggers transcriptional induction of genes, including those for amino acid transporters, with leucine being a potent inducer.
Purpose of the Study:
- To investigate the mechanism of amino acid sensing by Ssy1 in Saccharomyces cerevisiae.
- To determine if amino acid transport is a prerequisite for Ssy1-mediated signaling.
- To develop quantitative assays for measuring Ssy1-dependent amino acid sensing.
Main Methods:
- Generation and characterization of gain-of-function mutations in the SSY1 gene using a potassium uptake selection system.
- Analysis of Ssy1 function in response to various amino acids.
- Development of quantitative sensing assays involving Stp1 proteolytic processing and Western blot analysis.
Main Results:
- Gain-of-function mutations in SSY1 were identified, with some conferring inducer-independent signaling and others increasing apparent inducer affinity.
- These findings demonstrate that amino acid transport is not required for Ssy1-mediated signaling.
- Evidence supports direct interaction between Ssy1 and extracellular amino acids for sensing.
Conclusions:
- Ssy1 functions as a direct sensor of extracellular amino acids, independent of transport activity.
- The signal transduction pathway involves the proteolytic removal of an inhibitory domain from the transcriptional activator Stp1.
- Quantitative assays utilizing Stp1 processing provide a method for measuring Ssy1-mediated sensing.
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