Description
Heat-stable enterotoxins (STa) are small, cysteine-rich peptides secreted by Escherichia coli that are able to induce diarrhea through the stimulation of an intestine-specific receptor-guanylyl cyclase known as STaR. Binding of STa to STaR induces a dramatic increase in the cGMP content of the cell; the increase, in turn, inhibits salt absorption and stimulates chloride secretion. This imbalance of ions is accompanied by a massive accumulation of water in the gut that gives rise to the diarrhea and dehydration characteristic of enterotoxin activity. The hormonal form of guanylin is a 94-amino acid peptide with a molecular mass of 10.3kDa. Guanylin is synthesized by gut enterochromaffin cells as a prohormone of 115 amino acids and is processed to the molecular form of 94 amino acids circulating in the blood. GPVTVQDGNF SFSLESVKKL KDLQEPQEPR VGKLRNFAPI PGEPVVPILC SNPNFPEELK PLCKEPNAQE ILQRLEEIAE DPGTCEICAY AACTGC