GTPase that associates with the 50S ribosomal subunit and may have a role during protein synthesis or ribosome biogenesis. In vitro, also exhibits ATPase activity. Intrinsic GTPase activity is very slow and can be stimulated by the presence of 50S ribosomal subunits or 70S ribosomes. GTPase activity is inhibited by ATP. Monomer. Associates with the 50S ribosomal subunit. This interaction occurs in the presence of GTP, GDP, ATP or ADP, but not in their absence. May associate with membranes. Full-length protein is required for specific association with the 50S ribosomal subunit. Disruption does not affect lambda lysogeny or the transposition frequency of transposable elements. Belongs to the TRAFAC class OBG-HflX-like GTPase superfamily. HflX GTPase family.