The storage tissues of many plants contain protease inhibitors that are believed to play an important role in defending the plant from invasion by pests and pathogens. These proteinaceous inhibitor molecules belong to a number of structurally distinct families. We describe here the isolation, purification, initial inhibitory properties, and three-dimensional structure of a novel trypsin inhibitor from seeds of Veronica hederifolia (VhTI). The VhTI peptide inhibits trypsin with a submicromolar apparent K i and is expected to be specific for trypsin-like serine proteases. VhTI differs dramatically in structure from all previously described families of trypsin inhibitors, consisting of a helix-turn-helix motif, with the two ␣ helices tightly associated by two disulfide bonds. Unusually, the crystallized complex is in the form of a stabilized acyl-enzyme intermediate with the scissile bond of the VhTI inhibitor cleaved and the resulting N-terminal portion of the inhibitor remaining attached to the trypsin catalytic serine 195 by an ester bond. A synthetic, truncated version of the VhTI peptide has also been produced and co-crystallized with trypsin but, surprisingly, is seen to be uncleaved and consequently forms a noncovalent complex with trypsin. The VhTI peptide shows that effective enzyme inhibitors can be constructed from simple helical motifs and provides a new scaffold on which to base the design of novel serine protease inhibitors.Plant seeds are rich sources of proteinaceous proteinase inhibitors. These are believed to form a wide spectrum defense mechanism against fungal pathogens and invertebrate pests but may also play a role in the regulation of metabolism and act as storage proteins (1). A diverse range of medicinal properties have also been associated with many of these inhibitors, including anti-human immunodeficiency virus activity (2), hemolytic activity (3, 4), and inhibition of neurotensin binding (5) On the basis of their amino acid sequence and target proteinases, plant proteinase inhibitors have been classified into a number of families (6). The two best characterized are the Kunitz and Bowman-Birk families. The Kunitz soybean trypsin inhibitor was the first to be extensively characterized (7) and is an all ␤-sheet protein of 20 kDa. One exposed surface loop and the N terminus of the protein interact closely with the trypsin molecule, whereas the vast majority of the inhibitor forms no direct contacts with its inhibitory target. The Bowman-Birk family of serine protease inhibitors (reviewed in Ref. 8) are smaller proteins of ϳ8 kDa that contain seven conserved disulfide bridges. They have two reactive sites that are able to bind to the active sites of a number of serine proteases including trypsin and chymotrypsin from human, animal, and insect sources. The reactive site residues of the inhibitor lie within a ␤-hairpin region (stabilized by a disulfide bond), which enables them to be presented in the same conformation as the normal peptide substrate (9). Like the Kunitz family of serine protea...

The characterization of the promoter of a wheat (Triticum aestivum) cv. Cheyenne high molecular weight glutenin subunit (HMW subunit) gene, Glu-1D-1 is reported. The nucleotide sequence of the promoter from position -1191 to -650 with respect to the transcription start site was determined, to add to that already determined. Analysis of this region of the promoter revealed the presence of an additional copy of part of the primary enhancer sequence and sequences related to regulatory elements present in other wheat seed protein genes. A chimaeric gene was constructed comprising the 5' flanking region of the Glu-1D-1 gene from position -1191 to +58, the coding region of the UID:A (Gus) gene, and the nopaline synthase (Nos) gene terminator. This chimaeric gene was introduced into wheat (Triticum durum cv. Ofanto) by particle bombardment of inflorescence explants. Two independent transgenic lines were produced, and both showed expression of the Gus gene specifically in the endosperm during mid-development (first detected 10-12 d after anthesis). Histochemical analysis of homozygous T(2) seed confirmed this pattern of expression, and showed that expression was initiated first in the central lobes of the starchy endosperm, and then spread throughout the endosperm tissue, while no expression was detected in the aleurone layer. Native HMW subunit protein was detectable by Western analysis 12-14 d after anthesis, consistent with concurrent onset of activity of the native and introduced HMW subunit gene promoters.

The characterization of the promoter of a wheat (Triticum aestivum) cv. Cheyenne high molecular weight glutenin subunit (HMW subunit) gene, Glu-1D-1 is reported. The nucleotide sequence of the promoter from position -1191 to -650 with respect to the transcription start site was determined, to add to that already determined. Analysis of this region of the promoter revealed the presence of an additional copy of part of the primary enhancer sequence and sequences related to regulatory elements present in other wheat seed protein genes. A chimaeric gene was constructed comprising the 5' flanking region of the Glu-1D-1 gene from position -1191 to +58, the coding region of the UID:A (Gus) gene, and the nopaline synthase (Nos) gene terminator. This chimaeric gene was introduced into wheat (Triticum durum cv. Ofanto) by particle bombardment of inflorescence explants. Two independent transgenic lines were produced, and both showed expression of the Gus gene specifically in the endosperm during mid-development (first detected 10-12 d after anthesis). Histochemical analysis of homozygous T(2) seed confirmed this pattern of expression, and showed that expression was initiated first in the central lobes of the starchy endosperm, and then spread throughout the endosperm tissue, while no expression was detected in the aleurone layer. Native HMW subunit protein was detectable by Western analysis 12-14 d after anthesis, consistent with concurrent onset of activity of the native and introduced HMW subunit gene promoters.

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