Catalyzes the conversion of GTP to GDP through hydrolysis of the gamma-phosphate bond in GTP. Appears to have an intrinsic GTPase activity that is stimulated by ZC3H15/DFRP1 binding likely by increasing the affinity for the potassium ions. When hydroxylated at C-3 of 'Lys-22' by JMJD7, may bind to RNA and play a role in translation. Binds to microtubules and promotes microtubule polymerization and bundling that are required for mitotic spindle assembly during prophase to anaphase transition. GTPase activity is not necessary for these microtubule-related functions. GTP + H2O = GDP + H(+) + phosphate The GTPase activity is enhanced by potassium ions as well as by DFRP1 binding. Interacts (via its C-terminal) with TAL1. Interacts with DFRP1/ZC3H15; this interaction prevents DRG1 poly-ubiquitination and degradation by proteasome. DRG1-ZC3H15/DFRP1 complex co-sediments with polysomes. Interacts with STK16. Interacts with JMJD7. The DRG1-ZC3H15/DFRP1 complex associates with polysomes. The ThrRS, GTPase, SpoT (TGS) domain is not necessary for GTP binding nor for the GTPase activity. It appears to play a regulatory role favoring GTP hydrolysis mediated by DFRP1/ZC3H15. Sumoylated by UBE2I in response to MEKK1-mediated stimuli. Hydroxylated (with S stereochemistry) at C-3 of Lys-22 by JMJD7. Phosphorylated at Thr-100 by STK16. Polyubiquitinated; this modification induces proteolytic degradation and is impaired by interaction with ZC3H15. Belongs to the TRAFAC class OBG-HflX-like GTPase superfamily. OBG GTPase family.