Residual structure in islet amyloid polypeptide mediates its interactions with soluble insulin

The results from NMR analysis of islet amyloid polypeptide (IAPP), a 37-amino acid polypeptide hormone of the calcitonin family which is colocalized and cosecreted with insulin in secretory granules of pancreatic islet [beta] cells are presented. The data obtained from NMR chemical shifts, [super 5]N relaxation, and 49 ns replica exchange molecular dynamic simulations indicated that the transiently populated helical structure in residues 11?18 are essential for interactions with insulin.