Interferons induce a large number of genes in their target cells, including those coding for guanylate-binding proteins (GBPs). GBPs, such as GBP1, are characterized by their ability to specifically bind guanine nucleotides (GMP, GDP, and GTP) and are distinguished from the GTP-binding proteins by the presence of 2 binding motifs rather than 3 . The 593-amino acid GBP1 protein shares 77% and 88% identity with GBP2 and GBP3 , respectively. All GBPs, including GBP1, have a conserved N-terminal globular GTP-binding domain containing 2 consensus sequences and a third T(L/V)RD sequence not found in other GTPases. The GBP1 gene to the GBP gene cluster on chromosome 1p22.2. It is located telomeric to GBP2 and centromeric to GBP3. High expression of GBP1, GBP2, and GBP3 are in endothelial cells after stimulation with IFNG , TNF , or IL1B.