title: Crystallization and preliminary X-ray diffraction studies on a trypsin/chymotrypsin double-headed inhibitor from horse gram.
abstract: 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.
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore.
authors.forename: B
authors.initials: B
authors.lastname: Prakash
authors.forename: M R
authors.initials: MR
authors.lastname: Murthy
authors.forename: Y N
authors.initials: YN
authors.lastname: Sreerama
authors.forename: P R
authors.initials: PR
authors.lastname: Sarma
authors.forename: D R
authors.initials: DR
authors.lastname: Rao
mesh_terms: D002918:Chymotrypsin / Q000037:antagonists & inhibitors; D003460:Crystallization; D018360:Crystallography, X-Ray / Q000379:methods; D007887:Fabaceae; D008970:Molecular Weight; D010946:Plants, Medicinal; D012639:Seeds; D014357:Trypsin / Q000378:metabolism; D014358:Trypsin Inhibitor, Bowman-Birk Soybean / Q000737:chemistry* / Q000302:isolation & purification; D014961:X-Ray Diffraction / Q000379:methods
chemical_list: D014358:Trypsin Inhibitor, Bowman-Birk Soybean; D002918:Chymotrypsin; D014357:Trypsin