GTPase that associates with the 50S ribosomal subunit and may have a role during protein synthesis or ribosome biogenesis. Specific for GTP. GTPase activity is stimulated by the presence of 50S ribosomal subunits. Hydrolysis is probably regulated by the HflX N-terminal domain. Monomer. Associates with the 50S ribosomal subunit. Does not associate with 70S ribosomes. May associate with membranes. Belongs to the TRAFAC class OBG-HflX-like GTPase superfamily. HflX GTPase family.