cd01851

Guanylate-binding protein (GBP) family (N-terminal domain); Guanylate-binding protein (GBP), N-terminal domain. Guanylate-binding proteins (GBPs) define a group of proteins that are synthesized after activation of the cell by interferons. The biochemical properties of GBPs are clearly different from those of Ras-like and heterotrimeric GTP-binding proteins. They bind guanine nucleotides with low affinity (micromolar range), are stable in their absence and have a high turnover GTPase. In addition to binding GDP/GTP, they have the unique ability to bind GMP with equal affinity and hydrolyze GTP not only to GDP, but also to GMP. Furthermore, two unique regions around the base and the phosphate-binding areas, the guanine and the phosphate caps, respectively, give the nucleotide-binding site a unique appearance not found in the canonical GTP-binding proteins. The phosphate cap, which constitutes the region analogous to switch I, completely shields the phosphate-binding site from solvent such that a potential GTPase-activating protein (GAP) cannot approach.