The micro domain responsible for ligand-binding of guanylyl cyclase C.
Guanylyl cyclase C (GC-C), a member of membrane-bound guanylyl cyclases, is a receptor protein for guanylin and uroguanylin. The binding of a ligand to the extracellular domain of GC-C (ECD(GC-C)) triggers signal transduction, resulting in the regulation of intestinal fluids and electrolytes. A previous study proposed that a ligand-binding site on GC-C is localized near the transmembrane region. To further investigate the mechanism by which GC-C is activated, the C-terminal polypeptide (Met341-Gln407) of ECD(GC-C) (the micro domain), which includes the ligand-binding site, was over-expressed in Escherichia coli and its ligand-binding ability was examined. The micro domain showed ligand-binding activity (IC(50)=1 x 10(-8) M). This result clearly indicates that a ligand-binding site is located in close proximity to the membrane-bound region, and that the micro domain is capable of independently binding the ligand, without assistance from other domains. The use of this micro binding domain in the study of interactions between GC-C and ligands could be a useful tool and could lead to a better understanding of GC-C signal transduction.
Division of Organic Chemistry, Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan. yuji@protein.osaka-u.ac.jp
Yuji
Y
Hidaka
Yoshiko
Y
Matsumoto
Yasutsugu
Y
Shimonishi
D001665:Binding Sites; D001667:Binding, Competitive; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled; D018000:Receptors, Peptide / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D015183:Restriction Mapping
D008024:Ligands; D008565:Membrane Proteins; D018000:Receptors, Peptide; D011994:Recombinant Proteins; D006162:Guanylate Cyclase; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled