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Structurally reduced monosaccharide transporters in an evolutionarily conserved red alga
Silke Schilling1, Christine Oesterhelt
1Institut für Biochemie und Biologie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany.
The Biochemical Journal
|May 15, 2007
Summary
Galdieria sulphuraria utilizes multiple sugar transporters for nutrient uptake. Three transporters, GsSPT1, GsSPT2, and GsSPT4, were characterized, revealing distinct roles and transport mechanisms in this extremophilic alga.
Area of Science:
- * Plant Biology
- * Algal Physiology
- * Molecular Biology
Background:
- * The extremophilic red alga *Galdieria sulphuraria* is facultatively heterotrophic, relying on external nutrient uptake.
- * A diverse array of plasma membrane transporters facilitates the uptake of sugars and polyols.
- * Understanding these transporters is crucial for comprehending algal nutrient assimilation.
Purpose of the Study:
- * To clone and characterize three *Galdieria sulphuraria* sugar and polyol transporters (GsSPT1, GsSPT2, GsSPT4).
- * To investigate their transcriptional regulation and transport capacities.
- * To elucidate their functional mechanisms and substrate specificities.
Main Methods:
- * Cloning of three putative sugar transporter genes (GsSPT1, GsSPT2, GsSPT4).
- * Functional expression and transport assays in a heterologous yeast system.
- * Genetic complementation of a sugar uptake-deficient yeast mutant.
- * Analysis of substrate specificity, pH dependency, and kinetic parameters.
Main Results:
- * GsSPT1, GsSPT2, and GsSPT4 were confirmed as functional plasma membrane transporters in yeast.
- * GsSPT1 functions as a sugar/H(+) symporter, with glucose uptake being exclusive to it.
- * GsSPT2 and GsSPT4 exhibit broad substrate specificity and operate independently of pH, suggesting active transport mechanisms distinct from H(+) symport.
Conclusions:
- * *Galdieria sulphuraria* possesses a diverse set of functional sugar transporters with overlapping specificities.
- * GsSPT1, GsSPT2, and GsSPT4 play significant roles in the alga's heterotrophic nutrition.
- * The distinct characteristics of GsSPT2 and GsSPT4 suggest evolutionary divergence from ancestral H(+) symporter genes.
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