Dimeric crystal structure of a Bowman-Birk protease inhibitor from pea seeds.Li de la Sierra, I., Quillien, L., Flecker, P., Gueguen, J., Brunie, S.
(1999) J Mol Biol 285: 1195-1207
- PubMed: 9887273
- DOI: https://doi.org/10.1006/jmbi.1998.2351
- Primary Citation of Related Structures:
- PubMed Abstract:
The trypsin/chymotrypsin inhibitors from winter pea seeds (PsTI) are members of the Bowman-Birk protease inhibitor (BBPI) family. The crystal structure of the isoform PsTI-IVb was determined by molecular replacement at 2.7 A resolution using the X-ray co-ordinates of the soybean inhibitor as a search model. The inhibitor crystallized with a nearly perfect 2-fold symmetric dimer in the asymmetric unit. Although the overall structure is very similar to that seen in other BBPIs, there are notable new structural features. Unlike the previously reported X-ray structures of BBPIs, the structure of PsTI-IVb includes the C-terminal segment of the molecule. The C-terminal tail of each subunit is partly beta-stranded and interacts with the 2-fold symmetry-related subunit, forming a beta-sheet with strands A and B of this subunit. The dimer is mainly stabilized by a large internal hydrogen-bonded network surrounded by two hydrophobic links. Fluorescence anisotropy decay measurements show that residues Tyr59 and Tyr43 are mobile in the picosecond time scale with a large amplitude. The fluorescence study and a molecular model of the simultaneous binding of PsTI-IVb to porcine trypsin and bovine chymotrypsin are compatible only with a monomeric state of the functional molecule in solution.
Unité de Recherches de Biochimie et Structure des Protéines, INRA, Jouy-en-Josas Cedex, 78352, France.