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. 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). GTPase activity is not inhibited by ATP or GDP. Overexpression decreases cell growth starting in late log phase and continuing into stationary phase (PubMed:21352546). Monomer (By similarity). Interacts with anti-sigma-F factor RsbW, was not seen to interact with RelA (PubMed:21352546). Found to be entirely in cytoplasm (PubMed:22578863). Also found to be 90% associated with cell membrane, 10% in soluble extract. Associated with 30S and 50S ribosome subunits as well as 70S ribosomes (PubMed:21352546). Expression increases about 5-fold from early log phase to stationary phase, dropping in late stationary phase (at protein level). Autophosphorylates using GTP but not ATP; autophosphorylation requires Mg(2+), is inhibited by cold GTP and to a lesser extent GDP but not by ATP. Belongs to the TRAFAC class OBG-HflX-like GTPase superfamily. OBG GTPase family.