HOW IS PHEROMONE SPECIFICITY ENCODED IN PROTEINS

Pheromone specificity in the Lepidoptera is encoded in protein compone nts of the antennal sensillum lymph and dendritic membrane. In this pa per, we highlight recent work on the molecular determinants of pheromo ne binding affinity of pheromone binding proteins (PBPs) of three gene ra. First, we describe new cDNA sequences for Lymantria dispar (Lymant riidae) and Agrotis segetum (Noctuidae). These data enrich the conclus ions derived from our functional studies. Secondly, we indicate how pr eparation of multimilligram quantities of the recombinant PBP 'Apol-3' (originally from Antheraea polyphemus) has provided a platform (i) to determine the ligand binding sites using photoaffinity labeling, (ii) to conduct structural analysis by CD and NMR, and (iii) to measure bi nding affinities using a new binding assay. Thirdly, we describe the u se of expression-cassette PCR technology to prepare two related PBPs f rom Antheraea perneyi to test binding affinities of naturally-occurrin g homologous PBPs. Our results support a model in which ligand specifi city for chain length, double bond position, and terminal functionalit y is partially encoded in the PBPs. We propose that the final decoding is accomplished when the PBP-pheromone complex activates a G-protein coupled seven-transmembrane domain receptor that contains recognition sites for both the presented pheromone and the presenting PBP.