Zinc Interactions with a Soluble Mutated Rat Amylin to Mimic Whole Human Amylin: An Experimental and Simulation Approach to Understand Stoichiometry,Speciation and Coordination of the Metal Complexes |
| |
Authors: | Dr Antonio Magrì Dr Giovanni Tabbì Dr Giuseppe Di Natale Prof Diego La Mendola Dr Adriana Pietropaolo Prof Maria Antonietta Zoroddu Dr Massimiliano Peana Prof Enrico Rizzarelli |
| |
Institution: | 1. Consiglio Nazionale delle Ricerche, Istituto di Cristallografia, Via P. Gaifami 18, 95126 Catania, Italy;2. Dipartimento di Farmacia, Università di Pisa, Via Bonanno Pisano, 6, 56126 Pisa, Italy;3. Dipartimento di Scienze della Salute, Università “Magna Graecia” di Catanzaro, Campus Universitario, Viale Europa, 88100 Catanzaro, Italy;4. Dipartimento di Chimica e Farmacia, University of Sassari, Via Vienna 2, 07100 Sassari, Italy |
| |
Abstract: | Islet amyloid polypeptide (IAPP) is a hormone co-secreted with insulin and zinc from pancreatic β-cells. To overcome the low solubility of human IAPP, we characterized zinc complexes species formed with 1) a mutated form of rat-IAPP(1–37; R18 H) able to mimic the human IAPP, 2) the r-IAPP(1–37) and the IAPP(1–8) fragment. Stoichiometry, speciation and coordination features of zinc(II) complexes were unveiled by ESI-MS, potentiometry and NMR measurements combined with DFT and free-energy simulations. Mononuclear species start to form around pH 6; Zn2+ binds both His18 and N-amino terminus in rat-IAPP(1–37; R18 H). The in silico study allows us to assess not only a structured turn compact domain in r-IAPP(1–37) and r-IAPP(1–37; R18 H) featured by a different free energy barrier for the transition from the compact to elongated conformation upon the coordination of Zn2+, but also to bring into light a coordination shell further stabilized by noncovalent interactions. |
| |
Keywords: | DFT NMR spectroscopy noncovalent interactions potentiometry zinc |
|
|