Figure 4. Primary peptide structures of human guanylin and uroguanylin, Escherichia coli heat-stable enterotoxin (STa) and linaclotide. The lines connect the disulfide bonds between the cysteine residues. Note that two disulfide bonds are formed in the active conformation of human guanylin and uroguanylin and three disulfide bonds formed the active conformation of STa enterotoxin and linaclotide. The conservative peptide core domains with identical amino acids are marked by boxes.
