GTPase that plays an essential role in the late steps of ribosome biogenesis (By similarity). Has GTPase activity but no ATPase activity. GTP, GDP, and dGTP but not GMP, ATP, CTP, and UTP compete for GTP binding. At pH 7.5, 70 degrees Celsius, 5 mM MgCl(2) and 400 mM KCl. Associates with the 50S ribosomal subunit. Each G (guanine nucleotide-binding) domain has activity on its own; domain 1 is twice as active as domain 2. The G domains do not interact, instead each contacts the C-terminal KH-like domain which lies between them. Belongs to the TRAFAC class TrmE-Era-EngA-EngB-Septin-like GTPase superfamily. EngA (Der) GTPase family.