Salivary glands of blood sucking insects such as the stable fly (Diptera: Muscidae) secrete proteins with anticoagulant effects to facilitate blood feeding. We have dissected salivary glands from male and female stable flies for RNA extraction and cDNA library construction. Randomly selected cDNA clones from the library were sequenced. Two abundantly expressed genes were identified. One sequence encodes a protein similar to thrombostasin from the horn fly. The thrombostasin cDNA encodes a protein of 309 amino acid residues, which includes a putative 18-residue signal peptide and a 291-residue mature protein. The calculated molecular weight of this protein is 33,617 Da and the isoelectric point is 5.27. The deduced amino acid sequence of this mature protein shows 34% identity to thrombostasin, a thrombin inhibitor from the horn fly ( Haematobia irritans ). The other sequence encodes a protein with 57% identity to antigen 5 precursor from the salivary glands of the tsetse fly (Glossina morsitans morsitans ). This cDNA contains an open reading frame encoding a 260-residue protein. The protein sequence includes a putative 20-residue signal peptide and a 240-residue mature protein. The calculated molecular weight and pI for this protein are 26,833 Da and 8.75, respectively. Characterization of the two proteins, their expression in stable flies and their potential role in blood feeding are currently being studied.
Species 1: Diptera Muscidae Stomoxys calcitrans (stable fly)
Keywords: salivary glands, cDNA
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