Study of the Structure and Function of Bowman-Birk Inhibitor of Serine Proteases

Bowman-Birk型蛋白酶抑制剂家族及其与蛋白酶复合物的结构分析已经成功地进行了。抑制丝氨酸蛋白酶的Bowman-Birk抑制剂是具有60-80个氨基酸残基的小蛋白质。一个抑制剂分子有7个二硫键，并且含有很少的疏水残基。它由两个结构域组成，这两个结构域的氨基酸序列非常相似。2.3胰蛋白酶-AB-I （azuki bean inhibitor）复合物结构分析：azuki bean inhibitor AB-I抑制胰蛋白酶和凝乳胰蛋白酶。ab - 1与胰蛋白酶的配合物（1:1）形成适合x射线分析的精细晶体。该抑制剂仅能确定胰蛋白酶结合结构域。其中140个水分子，R = 0.20。包括Lys26在内的抑制剂的结合位点在胰蛋白酶活性中心通过几个氢键和范德华接触紧密结合。抑制剂结合位点的结构似乎非常稳定，几乎不会发生任何偏离稳定结构的情况，而这种稳定结构是诱导蛋白水解反应所必需的。3.3花生抑制剂A- ii的分析：该抑制剂分子的尺寸为45x15x15a，由两个结构非常相似的不同结构域组成。它们的结构也与ab - 1胰蛋白酶结合域的结构基本相同。这两个结构域由分子内伪双轴连接，并由两个相当灵活的肽链连接，每个结构域在分子边缘有一个蛋白酶结合位点。

The structure analyses of a family of the Bowman-Birk type protease inhibitors and their complexes with proteases have successfully been carried out. The Bowman-Birk inhibitors which inhibit serine proteases are small proteins with 60-80 amino acid residues. An inhibitor molecule has seven disulfide bridges, and contains very few hydrophobic residues. It consists of two domains, of which the amino acid sequences are very similar to each other.1. 2.3 A structure analysis of the trypsin-AB-I (azuki bean inhibitor) complex: Azuki bean inhibitor AB-I inhibits trypsin and chymotrypsin. The complex between AB-I and trypsin (1:1) gave fine crystals suitable for the X-ray analysis. Of the inhibitor only the trypsin-binding domain could be determined. Including 140 water molecules, R = 0.20. The binding site of the inhibitor including Lys26 is tightly bound in the trypsin active center by several hydrogen bonds and van der Waals contacts. The structure of the binding site of the inhibitor seems to be very stable, and any deviation from the stable structure which is necessary to induce a proteolytic reaction seems hardly to occur.2. 3.3 A analysis of peanut inhibitor A-II: The inhibitor molecule has the dimension of 45x15x15 A, and consists of two distinct domains of which the structures are very similar with each other. Their structures are also essentially the same as that of the AB-I trypsin-binding domain. The two domains are related by an intramolecular pseudo twofold axis, and linked by two rather flexible peptide chains, and each domain has one binding site for proteases at the edges of the molecule.