Hydrolyzes GTP to GMP in two consecutive cleavage reactions and predominantly uses GTP and not GDP or GMP as the substrate (By similarity). Confers protection to several pathogens, including the bacterial pathogens Listeria monocytogenes and Mycobacterium bovis BCG as well as the protozoan pathogen Toxoplasma gondii (By similarity). Promotes IFN-gamma-mediated host defense against bacterial infections by regulating oxidative responses and bacteriolytic peptide generation (By similarity). 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 (By similarity). Participates along with GBP1 in trafficking monoubiquinated protein cargo to autolysosomes for generating ubiquitin-derived antimicrobial peptides (By similarity). Required for disruption of the parasitophorous vacuole formed following T.gondii infection and subsequent killing of the parasite (By similarity). 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 (PubMed:33408175). GTP + H2O = GDP + H(+) + phosphate Monomer and dimer (By similarity). Interacts with CYBA, CYBA-CYBB complex and ATG4B (By similarity). Interacts (via GB1/RHD3-type G domain) with NCF2 and NCF2-NCF4 complex (By similarity). Up-regulated in response to influenza virus A infection. Belongs to the TRAFAC class dynamin-like GTPase superfamily. GB1/RHD3 GTPase family. GB1 subfamily.