Soluble proteins in chemosensory organs of phasmids

Soluble proteins of low molecular weight have been purified from chemosensory organs of five species of Phasmids. On the basis of their N-terminal amino acid sequences, two classes can be identified. Polypeptides of 14 and 15 kDa, expressed in the antennae and legs of Eurycantha calcarata and Extatosoma tiaratum, as well as in the antennae of Carausius morosus, bear a close similarity (around 45% identity) with a soluble protein associated with the sensilla coeloconica of Drosophila melanogaster. Two proteins of 19 and 18 kDa, isolated from the antennae and the maxillary palpi, respectively, of Acrophylla wuelfingi, are 59 and 75% identical, in their N-terminal region, to a 19 kDa antennal protein of Carausius morosus. Similarity between members of the two classes is not significant, being limited to two to three identical amino acids in the most favorable cases. Finally, a 17 kDa protein, specifically expressed in the antennae of Sipyloidea sipylus, did not show any homology with other proteins. The expression in sensory organs and the characteristics of these proteins may suggest a function in chemosensory transduction.