Positional Cyclization Scanning: A New Method to Evaluate the Bioactive Conformation of Glucagon
Glucagon is a polypeptide hormone, which consists of 29 amino acid residues. Secreted from pancreas, it has an importance role in glucose homeostasis. The conformation of glucagon has been examined by various biophysical methods including X-ray crystallography  and 2D-NMR spectroscopy . Although an amphiphilic helical conformation was observed at the C-terminal region of glucagon by both methods, the rest of the molecule displayed different conformations depending on the method used to examine them. The glucagon receptor is a G protein-coupled receptor (GPCR) which resides on the membrane surface, and unfortunately, it is still extremely difficult to examine a bioactive conformation of a ligand when it binds to its receptor. Therefore, in an attempt to obtain information about the bioactive conformation of glucagon, a new approach, “positional cyclization scanning”, was developed to determine secondary structures in the bioactive conformation.
KeywordsSecondary Structure Disulfide Bridge Adenylate Cyclase Activity Helical Conformation Polypeptide Hormone