PDBsum entry 1wbc

Serine protease inhibitor

PDB id: 1wbc

Contents

Protein chain

183 a.a. *

Waters ×56

* Residue conservation analysis

PDB id:

1wbc

Name:

Serine protease inhibitor

Title:

Crystallization and preliminary x-ray studies of psophocarpin b1, a chymotrypsin inhibitor from winged bean seeds

Structure:

Chymotrypsin inhibitor (wci). Chain: a

Source:

Psophocarpus tetragonolobus. Winged bean. Organism_taxid: 3891. Tissue: seed

Resolution:

2.95Å R-factor: 0.191

Authors:

J.K.Dattagupta,A.Podder,C.Chakrabarti,U.Sen,S.K.Dutta,M.Singh

Key ref:

J.K.Dattagupta et al. (1996). Structure of a Kunitz-type chymotrypsin from winged bean seeds at 2.95 A resolution. Acta Crystallogr D Biol Crystallogr, 52, 521-528. PubMed id: 15299674 DOI: 10.1107/S0907444996000224

Date:

30-Nov-95 Release date: 03-Apr-96

Protein chain

P10822  (ICW3_PSOTE) -  Chymotrypsin inhibitor 3 from Psophocarpus tetragonolobus

Seq: 207 a.a.

Struc: 183 a.a.

DOI no: 10.1107/S0907444996000224

Acta Crystallogr D Biol Crystallogr 52:521-528 (1996)

PubMed id: 15299674

Structure of a Kunitz-type chymotrypsin from winged bean seeds at 2.95 A resolution.

J.K.Dattagupta, A.Podder, C.Chakrabarti, U.Sen, S.K.Dutta, M.Singh.

ABSTRACT

Thc crystal structure of an alpha-chymotrypsin inhibitor (P6(1)22; a = 61.4, c = 210.9 A) isolated from winged bean (Psophocarpus. tetragonolobus) seeds has been determined at 2.95 A resolution by the molecular-replacement method using the 2.6 A coordinates of Erythrina trypsin inhibitor (ETI) as the starting model (57% sequence homology). This protease inhibitor, WCI, belongs to the Kunitz (STI) family and is a single polypeptide chain with 183 amino-acid residues having a molecular weight of 20 244 Da. Structure refinement with RESTRAIN and X-PLOR has led to a crystallographic R factor of 19.1% for 3469 observed reflections (I > 2sigma) in the resolution range 8-2.95 A. A total of 56 water molecules have been incorporated in the refined model containing 181 amino-acid residues. In the refined structure the deviations of bond lengths and bond angles from ideal values are 0.015 A and 2.2 degrees, respectively. The inhibitor molecule is spherical and consists of 12 antiparallel beta-strands with connecting loops arranged in a characteristic folding (a six-stranded beta-barrel and a six-stranded lid on one hollow end of the barrel) common to other homologous serine protease inhibitors in the Kunitz (STI) family as well as to some non-homologous proteins like interleukin-lalpha and interleukin-lbeta. In the structure the conformation of the protruding reactive-site loop is stabilized through hydrogen bonds mainly formed by the side chain of Asnl4, which intrudes inside the cavity of the reactive-site loop, with the side-chain and main-chain atoms of some residues in the loop region. A pseudo threefold axis exists parallel to the barrel axis of the structure. Each of the three subdomains comprises of four beta-strands with connecting loops.

Selected figure(s)

Figure 5.
Fig. 5. The hydrophobic core of the /3-barrel seen down the barrel axis.

Figure 6.
Fig. 6. Hydrogen bonding (indicated by lines) in the reactive- site loop. water O atom is indicated by a dark

The above figures are reprinted by permission from the IUCr: Acta Crystallogr D Biol Crystallogr (1996, 52, 521-528) copyright 1996.

Figures were selected by an automated process.