Soluble proteins from chemosensory organs of Eurycantha calcarata (Insects, Phasmatodea)

Three related nucleotide sequences, encoding mature proteins of 108-113 ami no acids, have been obtained from antennal cDNA of the Phasmid Eurycantha c alcarata. Among these, one is also expressed in the tarsi as demonstrated b y N-terminal sequence and mass spectrometric analyses of protein samples is olated from both organs. PCR experiments performed with specific primers, s howed that this species is also expressed in the mouth organs and in the cu ticle, while the other two are antennal specific. All three isoforms are si milar to Drosophila OS-D and other proteins reported in several insect orde rs, but one of them is significantly different from the other two. The best conserved elements are the N-terminal region and the four cysteine residue s. Accurate ESMS measurements indicated that all cysteines are involved in two disulphide bonds and ruled out the occurrence of additional posttransla tional modifications. Polyclonal antibodies, raised against the purified pr otein, did not react with proteins of the same class expressed in another P hasmid species, Carausius morosus, and in the orthopteran Schistocerca greg aria, nor did antibodies against these proteins recognise those of E. calca rata. (C) 2000 Elsevier Science Ltd. All rights reserved.