Structural highlights
Function[TKN1_SCYCA] Tachykinins are active peptides which excite neurons, evoke behavioral responses, are potent vasodilators and secretagogues, and contract (directly or indirectly) many smooth muscles. Publication Abstract from PubMedScyliorhinin I, a linear decapeptide, is the only known tachykinin that shows high affinity for both NK-1 and NK-2 binding sites and low affinity for NK-3 binding sites. As a first step to understand the structure-activity relationship, we report the membrane-induced structure of scyliorhinin I with the aid of circular dichroism and 2D-(1)H NMR spectroscopy. Sequence specific resonance assignments of protons have been made from correlation spectroscopy (TOCSY, DQF-COSY) and NOESY spectroscopy. The interproton distance constraints and dihedral angle constraints have been utilized to generate a family of structures using DYANA. The superimposition of 20 final structures has been reported with backbone pairwise root mean-square deviation of 0.38 +/- 0.19 A. The results show that scyliorhinin I exists in a random coil state in aqueous environments, whereas helical conformation is induced toward the C-terminal region of the peptide (D4-M10) in the presence of dodecyl phosphocholine micelles. Analysis of NMR data is suggestive of the presence of a 3(10)-helix that is in equilibrium with an alpha-helix in this region from residue 4 to 10. An extended highly flexible N-terminus of scyliorhinin I displays some degree of order and a possible turn structure. Observed conformational features have been compared with respect to that of substance P and neurokinin A, which are endogenous agonists of NK-1 and NK-2 receptors, respectively. Membrane-Induced Structure of Scyliorhinin I: A Dual NK1/NK2 Agonist.,Dike A, Cowsik SM Biophys J. 2005 May;88(5):3592-600. Epub 2005 Feb 24. PMID:15731392[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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