PDBsum entry 1c2a

Hydrolase inhibitor

PDB id: 1c2a

Contents

Protein chain

120 a.a. *

Waters ×41

* Residue conservation analysis

References listed in PDB file

Key reference

Title

Crystal structure of a 16 kda double-Headed bowman-Birk trypsin inhibitor from barley seeds at 1.9 a resolution.

Authors

H.K.Song, Y.S.Kim, J.K.Yang, J.Moon, J.Y.Lee, S.W.Suh.

Ref.

J Mol Biol, 1999, 293, 1133-1144. [DOI no: 10.1006/jmbi.1999.3239]

PubMed id

10547291

Abstract

The Bowman-Birk trypsin inhibitor from barley seeds (BBBI) consists of 125 amino acid residues with two inhibitory loops. Its crystal structure in the free state has been determined by the multiwavelength anomalous diffraction (MAD) method and has been refined to a crystallographic R-value of 19.1 % for 8.0-1.9 A data. This is the first report on the structure of a 16 kDa double-headed Bowman-Birk inhibitor (BBI) from monocotyledonous plants and provides the highest resolution picture of a BBI to date. The BBBI structure consists of 11 beta-strands and the loops connecting these beta-strands but it lacks alpha-helices. BBBI folds into two compact domains of similar tertiary structure. Each domain shares the same overall fold with 8 kDa dicotyledonous BBIs. The five disulfide bridges in each domain are a subset of the seven disulfide bridges in 8 kDa dicotyledonous BBIs. Two buried water molecules form hydrogen bonds to backbone atoms in the core of each domain. One interesting feature of this two-domain inhibitor structure is that the two P1 residues (Arg17 and Arg76) are approximately 40 A apart, allowing the two reactive-site loops to bind to and to inhibit two trypsin molecules simultaneously and independently. The conformations of the reactive-site loops of BBBI are highly similar to those of other substrate-like inhibitors. This structure provides the framework for modeling of the 1:2 complex between BBBI and trypsin.

Figure 6.
Figure 6. Stereo diagram showing the interactions between two buried water molecules and surrounding backbone atoms. (a) The N domain; (b) the C domain. The distances between the water molecule and its hydrogen bonding atoms of the inhibitor are given.

Figure 8.
Figure 8. A hypothetical model for the 1:2 complex between BBBI and two trypsin molecules. (a) The back- bone model of BBBI (green tubes) and the electrostatic potential surface of trypsin molecules. (b) The backbone model of trypsins (magenta tubes) and the electrostatic potential surface of BBBI. The view in (b) is obtained by a 180 ° rotation of (a) around a horizontal axis. Posi- tively charged regions are blue and negatively charged regions are red. The N and C-terminal and P1 residues in BBBI and the catalytic triad (Asp102-His57-Ser195) in trypsin are labeled. This Figure was generated using GRASP (Nicholls, 1992).

The above figures are reprinted by permission from Elsevier: J Mol Biol (1999, 293, 1133-1144) copyright 1999.

Secondary reference #1

Title

Preliminary X-Ray crystallographic analysis of bowman-Birk trypsin inhibitor from barley seeds.

Authors

H.K.Song, S.W.Suh.

Ref.

Acta Crystallogr D Biol Crystallogr, 1998, 54, 441-443. [DOI no: 10.1107/S0907444997010986]

PubMed id

9761922

Figure 1.
Figure 1 Photograph of tetragonal crystals of Bowman-Birk trypsin inhibitor from barley seeds. The crystal has approximate dimensions of 0.7 × 0.4 × 0.4 mm. See the text for detailed crystallization conditions.

The above figure is reproduced from the cited reference with permission from the IUCr