An essential GTPase which binds GTP, GDP and possibly (p)ppGpp with moderate affinity, with high nucleotide exchange rates and a fairly low GTP hydrolysis rate; the half-life of the GTP-bound state is about 50 minutes (PubMed:26122105). Plays a role in control of the cell cycle, stress response, ribosome biogenesis and in those bacteria that undergo differentiation, in morphogenesis control (By similarity). Optimal binding to GTP occurs between 5-10 mM Mg(2+), binding to GDP is inhibited at > 1 mM Mg(2+). Monomer. Associates with 50S ribosomal subunits. A small amount may associate with the cell inner membrane. Expressed constitutively, reaches maximum expression in early log phase and remains constant until stationary phase. Similar levels are seen when cells are grown under iron-limiting conditions, anoxically or in the presence of human serum, which mimic clinical infections (at protein level). Essential, it cannot be deleted. Belongs to the TRAFAC class OBG-HflX-like GTPase superfamily. OBG GTPase family.