Regulates intracellular concentrations of taurine and glutamate. Negatively modulates SLC1A1/EAAC1 glutamate transport activity by decreasing its affinity for glutamate in a PKC activity-dependent manner. May be involved in membrane traffic. Binds to prenylated RAB and Ras superfamily members. Also exists as a soluble form in the cytoplasm. Associated with microtubules. Belongs to the PRA1 family.