(357g) Invited Talk: Probing the Substrate Specificity of a Vacuolar Sugar Transporter

Unlike plasma membrane transporters, vacuolar membrane transporters are considerably more challenging to characterize given the fragility of this organelle and the low level of vacuolar proteins in a cell. Here we show a strategy to characterize vacuolar sugar transporters by first converting the proteins into biosensors. Our results show that the Arabidopsis thaliana vacuolar transporter SWEET2 has similar substrate specificity as its close homolog SWEET1, albeit displaying different affinities. Mutagenesis analysis suggests that the differences in affinity depend on non-specific interactions involving key residues in the binding pocket. Moreover, our new vacuolar biosensor can be an effective tool for monitoring sugar transport at vacuolar membranes that would be otherwise challenging to study.