PBAN-INDUCED SEX-PHEROMONE BIOSYNTHESIS IN HELIOTHIS-PELTIGERA - STRUCTURE, DOSE, AND TIME-DEPENDENT ANALYSIS

A structure-activity relationship study of Hez-PBAN was performed with respect to its pheromonotropic activity, using Heliothis peltigera as the test animal. The activity of N- and C-terminally derived sequence s was examined in a time- and dose-dependent mode. Using a variety of Hez-PBAN-derived fragments at two doses (1 and 10 pmol) and at differe nt times post-injection (5-120 min), we were able to demonstrate that peptides lacking 12 and 16 amino acids from their N-terminus are as po tent as the full length PBAN, and that the C-terminally derived hexape ptide was capable of stimulating sex pheromone production to a similar extent as PBAN 1-33NH(2), when its activity was analyzed at shorter p ost-injection times. Within the C-terminal sequence, the amide was fou nd to play a crucial role. In addition, it was observed that the regio n between amino acids 9 and 13 is important for the biological activit y of the full length PBAN. The fact that the pheromonotropic activity of the hexapeptide was similar to that of the full length PBAN, under specific conditions, suggests that this sequence constitutes the biolo gically active site of the neuropeptide. The discovery that PBAN-deriv ed peptides reacted in a time- and dose-dependent mode, strengthens th e assumption that proteolytic enzymes interfere with the pheromonotrop ic activity of the PBAN-derived fragments. The ability of a variety of peptides to stimulate sex pheromone biosynthesis suggests two possibl e mechanisms: (1) Existence of multiple pheromonotropic mechanisms whi ch may be mediated by multiple PBAN receptors that are activated at di fferent kinetics; (2) Existence of only one mechanism mediated by shor t C-terminally derived peptides. In the first case, the C-terminally d erived sequences fulfill the conformational requirement of only one cl ass of receptors, and other regions in the PBAN molecule (e.g., 9-13) fulfill the conformational requirements of a second (or other) class o f receptors. In the second case, the C-terminally derived sequence is the only conformationally important sequence, and other sequences, whi ch were found to be essential for the biological activity, serve other non-conformational purposes (e.g., protection against proteolytic deg radation). (C) 1995 Wiley-Liss, Inc.