Structural and functional characterization of eukaryotic SPX domains acting as molecular phosphate sensors

SPX domains, which are present in all eukaryotes, are found in proteins functionally associated with phosphate/polyphosphate metabolism, transport, storage and signaling and are perhaps acting as a molecular phosphate sensor. However, their molecular function remains to be elucidated.

I have already sucessfully crystallized a yeast and a human SPX domain and the structures indicate a possible phosphate binding pocket. The binding of inorganic phosphate by this small protein module can be analysed via a nuclear magnetic resonance based titration approach. The functionality of structure-based mutants will be investigated using the model plant Arabidopsis thaliana.

Elucidating the molecular function of the SPX domain will be a crucial step

towards a better understanding of phosphate sensing in eukaryotic cells. It may even provide a useful tool in overcoming Pi limitation in plant agriculture.