Facilitates the functional incorporation of the urease nickel metallocenter. Binds a maximum of 4 Ni(2+) and 2 Zn(2+) ions per homodimer. The affinity for Zn(2+) is 10-fold higher than that for Ni(2+). This process requires GTP hydrolysis. Homodimer; disulfide-linked. The physiological role of the disulfide bond has not been proven in vivo. UreD, UreF and UreG form a complex that acts as a GTP-hydrolysis-dependent molecular chaperone, activating the urease apoprotein by helping to assemble the nickel-containing metallocenter. Exists in a relatively unstructured form; binding to the other subunits (UreD, UreF and apourease) may induce correct protein folding. The presence of Zn2(+) or GTP does not alter the unfolded state. Belongs to the SIMIBI class G3E GTPase family. UreG subfamily.