Identification and cloning of odorant binding proteins from the scarab beetle Phyllopertha diversa

Wehave identified, cloned, and characterized two odorant binding proteins from the pale brown chafer, Phyllopertha diversa. One of the proteins (OBP1, 116 amino acids long) showed high amino acid identity (>90%) to two previously identified PBPs from scarab beetles. The second protein (OBP2) showed limited sequence similarity to lepidopteran and dipteran OBPs, but contained only 133 amino acids. Both proteins showed the occurrence of six highly conserved cysteines; electrospray mass spectral data suggested they are all bound in three disulfide bonds. During purification, OBP2 separated into several isoforms; N-terminal amino acid sequencing and electrospray ionization mass spectrometry demonstrated that they are different conformations of the same protein. In the native gel electrophoresis binding experiments, none of the OBPs bound 1, 3-dimethyl-2,4-(1H,3H)-quinazolinedione but different isoforms showed different binding affinities for (R)-japonilure, a pheromone from related scarab beetles, and bombykol, the pheromone from the silkworm moth, Bombyx mori. OBP1 also bound (R)-japonilure.