Journal Article

Crystal Structure of Bovine Trypsin and Wheat Germ Trypsin Inhibitor (I-2b) Complex (2:1) at 2.3 Å Resolution

S. Shanmuga Sundara Raj, Eiji Kibushi, Tatsuhiro Kurasawa, Atsuo Suzuki, Takashi Yamane, Shoji Odani, Yugo Iwasaki, Tsuneo Yamane and Tamaichi Ashida

in The Journal of Biochemistry

Published on behalf of The Japanese Biochemical Society

Volume 132, issue 6, pages 927-933
Published in print December 2002 | ISSN: 0021-924X
Published online December 2002 | e-ISSN: 1756-2651 | DOI: https://dx.doi.org/10.1093/oxfordjournals.jbchem.a003306
Crystal Structure of Bovine Trypsin and Wheat Germ Trypsin Inhibitor (I-2b) Complex (2:1) at 2.3 Å Resolution

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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 Å resolution to a final R-factor of 0.177. A distance of 37.2 Å 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 β-strands and the loops connecting these strands but it lacks α-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 β-strands, β1/β2 and β6/β7. Strands β1 and β6 are in direct contact with trypsin molecules and form stable triple stranded β-sheet structures via hydrogen bonds.

Keywords: Bowman-Birk type inhibitor; contiguous contact loop; double-headed inhibitor; trypsin inhibitor; wheat germ

Journal Article.  0 words. 

Subjects: Biochemistry

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