Identification and partial characterization of putative taurine receptor proteins from the olfactory organ of the spiny lobster.

To explore the initial stages of olfactory transduction, we have used biochemical techniques to characterize proteins associated with the dendritic plasma membrane from the olfactory receptor neurons of the spiny lobster Panulirus argus. In particular, we have studied proteins that interact with taurine, an amino acid that is an important odorant for this species. The cross-linker bis(sulfosuccinimidyl)suberate (BS3) was used to covalently link [3H]-taurine to cell surface proteins on membrane from the aesthetasc (olfactory) sensilla of the lateral filament of the antennule. A radioligand-receptor binding assay was used to show that this cross-linkage was highly specific for taurine at 0.2 mM BS3. In inhibition studies, of all the unlabeled odorants tested at excess concentrations (taurine, L-glutamate, adenosine-5'-monophosphate), only taurine significantly inhibited the cross-linkage of [3H]-taurine to the membrane. Membranes containing cross-linked proteins were solubilized, and proteins were separated on SDS-PAGE and examined with autoradiography. Bands with molecular weights of 100, 82, 62, 51, and 34kD were evident on the gels. However, only the 100 and 62 kD bands were consistently labeled with [3H]-taurine, and this labeling was completely inhibited in the presence of excess unlabeled taurine but not adenosine-5'monophosphate. The taurine-evoked behavioral search response of spiny lobsters was significantly reduced following treatment of their antennules with BS3 + taurine as compared with animals treated with BS3 alone, suggesting that the taurine-labeled binding proteins include taurine receptor proteins involved in the first stage of olfactory transduction.