Structural analysis of amylin and its analogs by NMR spectroscopy

Abstract

Amylin is a 37 residue peptide hormone, which is believed to be involved in metabolic diseases, such as diabetes. The studies presented in this dissertation were initially carried out on rat and human amylin, and later concentrated on pramlintide, an agonist of human amylin. The conformational preferences of these peptides in various solvent systems were determined mainly from chemical shift deviation (CSD) and nuclear Overhauser effect (NOE). An alpha-helix from residue 5 → 17 was present under all conditions examined. The Cys 2 - Cys7 disulfide loop appeared to be constrained and underwent slow exchange. The C-terminal portion of the peptide was very flexible. The solution structure of pramlintide in 25--35% of HFIP was also determined by XPLOR dynamics simulated annealing.The helical domain of amylin was further investigated, including the C-capping, disulfide nucleation, and specific site mutation effects. Ten amylin helix related peptides with various mutations were studied by both NMR and CD, and their helical propensity and stability were evaluated. Finally, a comparison study of amylin, calcitonin and calcitonin gene related peptide fragments is presented, and the similarities and differences among these biologically closely related peptides is discussed.