PDBsum entry 1pbi

Bowman-birk inhibitor

PDB id: 1pbi

Contents

Protein chains

68 a.a. *

Waters ×33

* Residue conservation analysis

PDB id:

1pbi

Name:

Bowman-birk inhibitor

Title:

Crystal structure of a bowman-birk inhibitor from pea seeds

Structure:

Bowman-birk proteinase inhibitor. Chain: a, b

Source:

Pisum sativum. Pea. Organism_taxid: 3888. Organ: seeds

Biol. unit:

Tetramer (from PQS)

Resolution:

2.70Å R-factor: 0.214 R-free: 0.272

Authors:

I.Li De La Sierra,S.Brunie

Key ref:

I.Li de la Sierra et al. (1999). Dimeric crystal structure of a Bowman-Birk protease inhibitor from pea seeds. J Mol Biol, 285, 1195-1207. PubMed id: 9887273 DOI: 10.1006/jmbi.1998.2351

Date:

20-Aug-98 Release date: 27-Jan-99

Protein chains

P56679  (IBBB_PEA) -  Seed trypsin/chymotrypsin inhibitor IVB from Pisum sativum

Seq: 72 a.a.

Struc: 68 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

DOI no: 10.1006/jmbi.1998.2351

J Mol Biol 285:1195-1207 (1999)

PubMed id: 9887273

Dimeric crystal structure of a Bowman-Birk protease inhibitor from pea seeds.

I.Li de la Sierra, L.Quillien, P.Flecker, J.Gueguen, S.Brunie.

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.

Selected figure(s)

Figure 3.
Figure 3. Hydrogen bond network of the interfacial domain of the dimer. Only relevant residues are shown in white for one subunit and black for the second sub- unit.

Figure 5.
Figure 5. (a) Molecular model of the PsTI/trypsin/chymotrypsin ternary complex showing the independent and non-interacting trypsin and chymotrypsin sites. This model is consistent with simultaneous binding of the two pro- teases. The PsTI molecule is shown in a green ribbon diagram, the molecular surfaces (calculated with the pro- gramme GRASP) of trypsin and chymotrypsin are in yellow and blue, respectively. (b) Main interactions between PsTI and trypsin. Hydrogen bonds are represented with broken lines. PsTI is in black and trypsin in white. (c) View showing the complementarity between the phenyl ring of Tyr43 and the S1 pocket of chymotrypsin. The alpha-car- bon trace of PsTI as well as all atoms of residue Tyr43, are shown in green. Residues of chymotrypsin which under- line the pocket are in light blue. The S1 pocket of chymotrypsin is represented as a transparent surface. This illustration was prepared using the programmes MOLSCRIPT, GRASP and RASTER3D (Merritt & Murphy, 1994).

The above figures are reprinted by permission from Elsevier: J Mol Biol (1999, 285, 1195-1207) copyright 1999.

Figures were selected by an automated process.