Prakash B, Murthy M R, Sreerama Y N, Sarma P R, Rao D R
Molecular Biophysics Unit, Indian Institute of Science, Bangalore.
J Mol Biol. 1994 Jan 7;235(1):364-6. doi: 10.1016/s0022-2836(05)80041-5.
The Bowman-Birk family of proteinase inhibitors from seeds of leguminous plants usually have a molecular mass of 8000 to 10,000 Da. Horse gram (Dolichos bifloros or Macrotyloma uniflorum) seeds contain an unusual Bowman-Birk inhibitor of molecular mass 15,500 Da active against both trypsin and chymotrypsin. In order to elucidate its three-dimensional structure, its evolutionary relationship with the more usual Bowman-Birk inhibitors and to study the structure-function properties, this inhibitor has been purified and crystallized. The purified protein crystallizes easily under a variety of conditions in different crystal forms. Crystals obtained by precipitating the protein (3 to 5 mg/ml in 50mM Tris.HCl (pH 8.0)) with 5% ammonium sulphate and 2 to 3% PEG 4000 appear to be suitable for structure determination by X-ray diffraction. The crystals belong to cubic space group P2(1)3 (a = 110.81 A) and diffract X-rays to beyond 3.0 A resolution.
豆科植物种子中的鲍曼-伯克蛋白酶抑制剂家族通常分子量为8000至10,000道尔顿。马豆（双花扁豆或单花大翼豆）种子含有一种不同寻常的鲍曼-伯克抑制剂，分子量为15,500道尔顿，对胰蛋白酶和胰凝乳蛋白酶均有活性。为了阐明其三维结构、与更常见的鲍曼-伯克抑制剂的进化关系以及研究结构-功能特性，已对该抑制剂进行了纯化和结晶。纯化后的蛋白质在多种条件下容易以不同晶体形式结晶。通过用5%硫酸铵和2至3%聚乙二醇4000沉淀蛋白质（在50mM Tris.HCl（pH 8.0）中为3至5mg/ml）获得的晶体似乎适合通过X射线衍射进行结构测定。这些晶体属于立方空间群P2(1)3（a = 110.81 Å），并且能将X射线衍射到3.0 Å以上的分辨率。
