Revealing the membrane-bound structure of neurokinin A using neutron diffraction

Neurokinin A (or substance K) belongs to the tachykinin family, a group of small amphipathic peptides that bind to specific membrane-embedded, G-prote in coupled receptors. The agonist/receptor complex is quaternary in nature because the receptor binding sites are thought to be located within the lip id bilayer and because the role of water cannot be ignored. The cell membra ne acts as a solvent to accumulate peptide and an inducer of peptide second ary structure. The three-dimensional shape that the peptide assumes when as sociated to the cell membrane will be an important parameter with regards t o the receptor selectivity and affinity. Neutron diffraction measurements w ere carried out in order to define the location of the N-terminus of the pe ptide in synthetic phospholipid multi-bilayer stacks. (C) 2000 Elsevier Sci ence B.V. All rights reserved.