Hydrolyzes GTP to GMP in 2 consecutive cleavage reactions, but the major reaction product is GDP (By similarity). Exhibits antiviral activity against influenza virus. Promotes oxidative killing and delivers antimicrobial peptides to autophagolysosomes, providing broad host protection against different pathogen classes (By similarity). Confers protection to the protozoan pathogen Toxoplasma gondii (By similarity). GTP + H2O = GDP + H(+) + phosphate Homodimer; homodimerization occurs upon GTP-binding and is required for the association with membranous structures. Heterodimer with other family members, including GBP1, GBP3, GBP4 and GBP5. GBP2-GBP5 dimers localize to the Golgi apparatus. Widely expressed. By IFNG. Isoprenylation is required for proper subcellular location. Belongs to the TRAFAC class dynamin-like GTPase superfamily. GB1/RHD3 GTPase family. GB1 subfamily. Extended N-terminus.