Crystal structure of bovine trypsin and wheat germ trypsin inhibitor (I-2b) complex (2:1) at 2.3 a resolution.
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.
Raj
S Shanmuga Sundara
SS
Venture Business Laboratory and Department of Biotechnology, Graduate School of Engineering, Nagoya University, Chikusa-ku, Nagoya 464-8603, Japan.
Kibushi
Eiji
E
Kurasawa
Tatsuhiro
T
Suzuki
Atsuo
A
Yamane
Takashi
T
Odani
Shoji
S
Iwasaki
Yugo
Y
Yamane
Tsuneo
T
Ashida
Tamaichi
T
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
D046911:Macromolecular Substances; D010940:Plant Proteins; C051542:wheat germ trypsin inhibitor; D014357:Trypsin