Involved in the biogenesis of the 60S ribosomal subunit and translational activation of ribosomes. Together with the EF-2-like GTPase RIA1, may trigger the GTP-dependent release of TIF6 from 60S pre-ribosomes in the cytoplasm, thereby activating ribosomes for translation competence by allowing 80S ribosome assembly and facilitating TIF6 recycling to the nucleus, where it is required for 60S rRNA processing and nuclear export. Associates with the 60S ribosomal subunit. Present with 5060 molecules/cell in log phase SD medium. Belongs to the SDO1/SBDS family.