title: Crystal structure of bovine trypsin and wheat germ trypsin inhibitor (I-2b) complex (2:1) at 2.3 a resolution.
abstract: The Bowman-Birk trypsin inhibitor (BBI) from wheat germ (I-2b) consists of 123 amino acid residues with two inhibitory loops. The crystal structure of a bovine trypsin-wheat germ trypsin inhibitor (I-2b) complex (2:1) has been determined at 2.3 A resolution to a final R-factor of 0.177. A distance of 37.2 A between the contiguous contact loops allows them to bind and inhibit two trypsin molecules simultaneously and independently. Each domain shares the same overall fold with 8 kDa BBIs. The five disulfide bridges in each domain are a subset of seven disulfide bridges in the 8 kDa BBIs. I-2b consists of ten beta-strands and the loops connecting these strands but it lacks alpha-helices. The conformations of the contiguous contact loops of I-2b are in a heart-like structure. The reactive sites in both domains, Arg 17 and Lys 76, are located on the loop connecting anti-parallel beta-strands, beta 1/beta 2 and beta 6/beta 7. Strands beta 1 and beta 6 are in direct contact with trypsin molecules and form stable triple stranded beta-sheet structures via hydrogen bonds.
authors.affiliation: Venture Business Laboratory and Department of Biotechnology, Graduate School of Engineering, Nagoya University, Chikusa-ku, Nagoya 464-8603, Japan.
authors.forename: S Shanmuga Sundara
authors.initials: SS
authors.lastname: Raj
authors.forename: Eiji
authors.initials: E
authors.lastname: Kibushi
authors.forename: Tatsuhiro
authors.initials: T
authors.lastname: Kurasawa
authors.forename: Atsuo
authors.initials: A
authors.lastname: Suzuki
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamane
authors.forename: Shoji
authors.initials: S
authors.lastname: Odani
authors.forename: Yugo
authors.initials: Y
authors.lastname: Iwasaki
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Yamane
authors.forename: Tamaichi
authors.initials: T
authors.lastname: Ashida
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D018360:Crystallography, X-Ray; D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D016415:Sequence Alignment; D014357:Trypsin / Q000737:chemistry* / Q000378:metabolism
chemical_list: D046911:Macromolecular Substances; D010940:Plant Proteins; C051542:wheat germ trypsin inhibitor; D014357:Trypsin