A novel Drosophila serpin that inhibits serine proteases

Serpins define a large protein family in which mast members function as ser ine protease inhibitors, Here we report the results of a search for serpins in Drosophila melanogaster that are potentially required for oogenesis or embryogenesis. We cloned and sequenced ovarian cDNAs that encode sir distin ct proteins haring extensive sequence similarity to mammalian serpins, incl uding residues important in the serpin inhibition mechanism. One of these n ew serpins in recombinant form inactivates, and complexes with, trypsin-lik e proteases in vitro. To our knowledge, these results represent the first e vidence for a serpin in Drosophila that functions as a serine protease inhi bitor. (C) 2000 Federation of European Biochemical Societies.