Involved in the maturation of [NiFe] hydrogenases. Required for nickel insertion into the metal center of the hydrogenase. Exhibits a low intrinsic GTPase activity, which is essential for nickel insertion. Strains missing this gene do not produce hydrogenase or urease; addition of Ni(2+) to cell cultures compensates only poorly for this loss of function. Normal amounts of apo-urease are produced by the cells. Belongs to the SIMIBI class G3E GTPase family. HypB/HupM subfamily.