Scarab beetles from the subfamily Rutelinae utilizean unusual group of lactones (5-alkenyl i-dilivdrofuranones, figure) as their sex pheromones (Leal, 1996). These compounds differ primarily in length of the alkenyl side chain and the stereochemistry at the ciliral center. Enantiomers frequently have opposite behavioral effects - the unnnatural stereoisomer inilibits male responses. Since various species utilize various stereoisomers, this provides an effective way for preventing iterspecies attraction.
It has been demonstrated recently in Lepidoptera that pheromone binding proteins bind various components of the pheromone blend with different affinities depending on ligand length, double bond positition or functional group (Du and Preswich, 1995). Since chirality seems to play such an important role for pheromone recognition in scarab beettles we intend to find out whether these species also possess PBPs and whether these proteins are able to discriminate between different ligands.
Both enantiomers of the two most common pheromones (japonilure-Z-5-(dec-1-
enyl)oxacyclopentan-2-one and buibuilactone -Z-5-(oct-1-enyl)oxacyclopentan-2-one)
have been prepared in tritiated form by stereoselective synthesis of
precursors and catalytic reduction of the corresponding alkyne.
Antennae-specific proteins have been detected in several species
(Popillia japonica, Anomala cuprea, and Anomala octiescostata).
N-terminal sequences of these proteins show moderate homology (47%) to
Drosophilia putative pheromone binding protein (McKenna et al., 1994)
but no signifficant similarity with lepidopteran PBPs. Obtaining their full
amino acid sequences via molecular cloning and binding studies with recombinant
proteins may lead to identification of structural elements involved in discrimination
of stereoisomers.
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