Guanylate Cyclase Activator 2B (GUCA2B)

Uroguanylin and guanylin (GUCA2A), peptide homologs of the bacterial heat-stable enterotoxins (e.g., the E. coli ST toxin; STa), are endogenous activators of the guanylate cyclase-2C receptor (GUCY2C), which synthesizes cyclic GMP (cGMP), a key component of several intracellular signal transduction pathways.The 16 C-terminal amino acids are identical to uroguanylin, and 8 of 13 C-terminal residues are conserved between GCAP II, uroguanylin, and E. coli STa.

The GUCA2B gene also has multiple binding sites for the promoter-specific transcription factors AP1 and AP2, and a cAMP-regulated enhancer element. In the mouse, uroguanylin mRNA is most prominent in the proximal small intestine, whereas guanylin mRNA is predominantly expressed in distal small intestine and colon.