Interaction of tachykinins with phospholipid membranes: A neutron diffraction study

Tachykinins are a group of peptides which bind to G-protein-coupled receptors, Receptor affinity appears to depend on different secondary structures of tachykinin which share the same hydrophobic carboxy-terminal sequence, FXGLM. Receptor activation is thought to be due to the carboxy-terminal submerging into the bilayer and the amino-terminal binding on the surface. Binding of tachykinins to phospholipid bilayers may take place both on the aqueous membrane surface and in the hydrophobic region, The two-state equilibrium appears to depend on the surface charge of the membrane. Deuterating substance P and neurokinin A at their carboxy-terminals, our results show two populations of label for each peptide. One is very close to the water-hydrocarbon interface, the other some 13 Angstrom deeper. We report that the bilayer location of the two tachykinins is remarkably similar, thereby inferring that receptor specificity must be controlled by finer levels of structure. (C) 1998 Elsevier Science B.V. All rights reserved.