The study of the conformation and interaction of two tachykinin peptides in membrane mimicking systems by NMR spectroscopy and pulsed field gradient diffusion

Pulsed-field gradient diffusion has been used to study the binding of two tachykinin Peptides, [Tyr(8)]-substance P (SP) and [Tyr(0)]-neurokinin A (NKA) to two membrane-mimicking micelles, dodecylphosphocholine, and sodium dodecylsulfate. The structure of these Peptides bound to the micelles have also been studied by using two-dimensional nmr and restrained simulated annealing calculations. No major difference in the structures of each peptide in the two micellar media was found. The difference between the micelle-bound structure of [Tyr(8)]SP and that of SP was also minor. The longer helical conformation on the C-terminus for [Tyr(0)]NKA was observed, compared with that for NKA. The relationship between the difference in the biological potencies of [Tyr(8)]SP and SP and the differences in their structure, especially the interaction of the side chains of the two aromatic residues, and the difference in their binding affinities to membrane was discussed. In addition, differences between the result of restrained molecular dynamics simulations of [Tyr(8)]SP in the presence of an explicit micelle and the present results were observed and discussed.