Required for 40S ribosomal subunit synthesis. Required for normal export of the pre-40S particles from the nucleus to the cytoplasm. Its subcellular location and association with pre-40S subunitshifts from mixed cytoplasm/nucleus to all nuclear in RPS19 disruptions, suggesting it acts after the ribosomal protein. Interacts with RIO2. Present with 1390 molecules/cell in log phase SD medium. Belongs to the TRAFAC class translation factor GTPase superfamily. Bms1-like GTPase family. TSR1 subfamily.