Evidence for a C‐terminal turn in PBAN An NMR and distance geometry study

Abstract

The solution conformation of the pheromone biosynthesis activating neuropeptide (PBAN) of the moth Helicoverpa zea has been determined using homonuclear two‐dimensional nuclear magnetic resonance techniques and distance geometry‐restrained energy minimization. The insect peptide hormone showed a random distribution of conformers in aqueous solution, whereas in a less polar medium of trifluoroethanol and water, a reordering process was observed. In particular, the C‐terminal region (Phe‐Ser‐Pro‐Arg‐Leu‐NH2) adopts a type I′β‐turn conformation, residues 20‐27 are in a helix conformation, and residues 1‐19 exhibit a high degree of flexibility. Direct observation of the C‐terminal β‐turn configuration of PBAN is consistent with a previous report that showed a rigid, cyclic analog of the C‐terminal pentapeptide of PBAN retained pheromonotropic activity [Nachman, R.J., Kuniyoshi, H., Roberts, V.A., Holman, G.M. & Suzuki, A. (1993). Biochem. Biophys. Res. Commun. 661‐666], Furthermore, our results show no interaction between the C‐terminal turn and the rest of the polypeptide chain, thus providing further evidence that the C‐terminal turn is indeed the important conformation recognized by the PBAN receptor. © Munksgaard 1996.

Identification of Functionally Important Residues of the Silkmoth Pheromone Biosynthesis-activating Neuropeptide Receptor, an Insect Ortholog of the Vertebrate Neuromedin U Receptor

“…Our decision to model the backbone conformation of C5PBAN/C5NMU as a type I ␤-turn was based on NMR structural analyses of PBAN (43,44) and a pheromonotropic eightresidue cyclic peptide containing a highly similar sequence to C5PBAN (underlined), cyclo(NTSFTPRL) (42,44). The docking simulations of C5PBAN-PBANR and C5NMU-NMUR1 highlighted the functional relevance of this conformation in both PBAN and NMU binding.…”

“…We were particularly interested in the molecular interactions between C5PBAN and the residues we determined experimentally to be critical for binding and activation. Simulations were performed using C5PBAN with a type I ␤-turn as NMR studies of PBAN have suggested that the C-terminal active site of PBAN adopts a ␤-turn (42)(43)(44). The ligand-binding pocket of the PBANR molecular models, however, was too small to fully accommodate C5PBAN with the type I ␤-turn conformation.…”