Potent activity of a PK/PBAN analog with an (E)-alkene, trans-Pro mimic identifies the Pro orientation and core conformation during interaction with HevPBANR-C receptor

The pyrokinin/pheromone biosynthesis activating neuropeptide (PK/PBAN) family plays a multifunctional role in an array of important physiological processes in insects, including regulation of sex pheromone biosynthesis in moths. A cyclic PK/PBAN analog (cyclo[NTSFTPRL]) retains significant activity on the pheromonotropic HevPBANR receptor from the tobacco budworm Heliothis virescens expressed in CHO-K1 cells. Previous studies indicate that this rigid, cyclic analog adopts a type I β-turn with a transPro over residues TPRL within the core PK/PBAN region. An analog containing an (E)-alkene, trans-Pro mimetic motif was synthesized, and upon evaluation on the HevPBANR receptor found to have an EC50 value that is not statistically different from a parent C-terminal PK/PBAN hexapeptide sequence. The results, in aggregate, provide strong evidence for the orientation of Pro and the core conformation of PK/PBAN neuropeptides during interaction with the expressed PBAN receptor. The work further identifies a novel scaffold with which to design mimetic PBAN analogs as potential leads in the development of environmentally favorable pest management agents capable of disrupting PK/PBAN-regulated pheromone signaling systems.