Book of Abstracts: Albany 2007

category image Albany 2007
Conversation 15
June 19-23 2007

Structural Characterization of Neurokinin-3 Receptor Selective Peptide Agonist Scyliorhinin II Bound to DPC Micelles

Scyliorhinin II, a cyclic Tachykinin peptide is a potent NK3 receptor agonist. The pharmacology of NK3 receptor is least characterized out of the three tachykinin receptor subtypes cloned and characterized for Tachykinins. To understand the structural basis of peptide-receptor interaction, the three-dimensional structure of the Scyliorhinin II in aqueous and micellar environment has been studied by two-dimensional proton nuclear magnetic resonance (2D 1H-NMR spectroscopy) and distance geometry calculations. Proton NMR assignments have been carried out with the aid of correlation spectroscopy (gradient-COSY and TOCSY) and nuclear Overhauser effect spectroscopy (NOESY and ROESY) experiments. The inter proton distances and dihedral angle constraints obtained from the NMR data have been used in torsion angle dynamics algorithm for NMR applications (DYANA) to generate a family of structures, which have been refined using restrained energy minimization and dynamics. The results show that in aqueous environment Scyliorhinin II lacks a definite secondary structure. The structure is well defined in presence of dodecyl phosphocholine micelles. The global fold of Scyliorhinin II bound to DPC micelles consists of a well defined helix in the C-terminal region from residue 12-18 and a series of turns towards N-terminus. The structure is further stabilized by disulfide bond between Cys7 and Cys13. The conformational range of the peptide revealed by NMR and CD studies has been analyzed in terms of characteristic secondary features. Observed conformational features have been compared to that of Substance P, Neurokinin A and Neurokinin B, potent NK1, NK2 and NK3 agonists, respectively.

Anjali Dike
Sudha M. Cowsik*

School of Life Sciences
Jawaharlal Nehru University
New Delhi-110067, India

*Email: scowsik@yahoo.com