Journal article
Hyper- and hyporesponsive mutant forms of the Saccharomyces cerevisiae Ssy1 amino acid sensor
The Saccharomyces cerevisiae integral membrane protein Ssy1p functions with Ssy5p and Ptr3p to sense extracellular amino acids. Signal transduction leads to processing and nuclear localization of Stp1p and Stp2p, transcriptional activators of many amino acid transporter genes. Ssy1p is structurally related to amino acid permeases, but unable to transport amino acids.
We isolated SSY1 mutants that constitutively activate a target promoter. Dose-response analysis showed that the mutants are hyperresponsive, requiring less inducer to give strong signaling than does the wild type. Another mutant (Ssy1pT639I) turned out to be hyporesponsive, i.e., it signals only at high inducer concentration.
In accordance with a transporter-like mechanism for Ssy1p function we suggest that the hyper- and hyporesponsive mutant forms differ from the wild-type sensor by being more and less inclined, respectively, to adopt an outward-facing, signaling conformation. Coordinate conformational dynamics of the sensor complex was supported by additive effects of combinations of constitutive SSY1, PTR3 and SSY5 alleles.
Assuming structural similarity of Ssy1p to the distantly related bacterial leucine transporter LeuTAa, several activating substitutions were located near the substrate binding site while others were on the periphery of Ssy1p. We suggest analyses of transporter-like sensors as an approach to understand key features of transporters.
Language: | English |
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Year: | 2008 |
Pages: | 164-176 |
ISSN: | 14645203 and 09687688 |
Types: | Journal article |
DOI: | 10.1080/09687680701771917 |
ORCIDs: | Kielland-Brandt, Morten |
neurotransmitter transporter homologue LeuT(Aa) nutrient sensing receptor affinity sensor protein complex signal transduction
AGP1 protein, S cerevisiae Alleles Amino Acid Sequence Amino Acid Substitution Amino Acid Transport Systems, Neutral Amino Acids Gene Expression Regulation, Fungal Intracellular Signaling Peptides and Proteins Membrane Proteins Models, Biological Molecular Sequence Data Mutant Proteins Mutation Nuclear Proteins Promoter Regions, Genetic Protein Binding Protein Processing, Post-Translational Protein Structure, Secondary RNA-Binding Proteins SSY1 protein, S cerevisiae STP1 protein, S cerevisiae Saccharomyces cerevisiae Saccharomyces cerevisiae Proteins Sequence Analysis, DNA Signal Transduction Transcription Factors