Involved in the biogenesis of the 60S ribosomal subunit and translational activation of ribosomes. Together with SBDS, triggers the GTP-dependent release of EIF6 from 60S pre-ribosomes in the cytoplasm, thereby activating ribosomes for translation competence by allowing 80S ribosome assembly and facilitating EIF6 recycling to the nucleus, where it is required for 60S rRNA processing and nuclear export. Has low intrinsic GTPase activity. GTPase activity is increased by contact with 60S ribosome subunits (By similarity). Associates with the 60S ribosomal subunit. Found in a complex consisting of the 60S ribosomal subunit, SBDS and EFL1. Belongs to the TRAFAC class translation factor GTPase superfamily. Classic translation factor GTPase family.