Catalyzes the conversion of GTP to GDP through hydrolysis of the gamma-phosphate bond in GTP. When hydroxylated at C-3 of 'Lys-21' by JMJD7, may bind to RNA and play a role in translation. . This is the function of DRG2 (developmentally regulated GTP binding protein 2, Ensembl gene identifier ENSG00000108591).