Hydrolyzes GTP to GMP in two consecutive cleavage reactions and predominantly uses GTP and not GDP or GMP as the substrate (PubMed:21551061, PubMed:31689351). Confers protection to several pathogens, including the bacterial pathogens Listeria monocytogenes and Mycobacterium bovis BCG as well as the protozoan pathogen Toxoplasma gondii (PubMed:21551061, PubMed:31964735, PubMed:18025219). Promotes IFN-gamma-mediated host defense against bacterial infections by regulating oxidative responses and bacteriolytic peptide generation (PubMed:21551061). May help to assemble NADPH oxidase on phagosomal membranes by acting as a bridging protein between NADPH oxidase cytosolic subunits NCF2-NCF4 and the membrane subunits CYBA-CYBB (PubMed:21551061). Participates along with GBP1 in trafficking monoubiquinated protein cargo to autolysosomes for generating ubiquitin-derived antimicrobial peptides (PubMed:21551061). Required for disruption of the parasitophorous vacuole formed following T.gondii infection and subsequent killing of the parasite (PubMed:31964735). Facilitates influenza A virus replication by inhibiting the activation of NF-kappaB and JAK-STAT signaling pathways and the expression of type I, type III interferons and pro-inflammatory cytokines (By similarity). GTP + H2O = GDP + H(+) + phosphate Inhibited by orthovanadate, berylium fluoride and aluminum flouride. Monomer and dimer (PubMed:31689351). Interacts with CYBA, CYBA-CYBB complex and ATG4B (PubMed:21551061). Interacts (via GB1/RHD3-type G domain) with NCF2 and NCF2-NCF4 complex (PubMed:21551061). By IFNG/IFN-gamma and IFNB1/IFN-beta (PubMed:18025219). Up-regulated upon infection by T.gondii or L.monocytogenes (PubMed:18025219). Up-regulated in response to influenza virus A infection (PubMed:33408175). Mice show a dramatic susceptibility to T. gondii infection, resulting in rapid death of infected mice in the acute phase of infection. A significantly increased parasite load seen in the spleen, liver and the peritoneal fluid, with markedly elevated production of pro-inflammatory cytokines and development of severe ascites. Belongs to the TRAFAC class dynamin-like GTPase superfamily. GB1/RHD3 GTPase family. GB1 subfamily. Truncated N-terminus. Extended N-terminus.