PDBsum entry 2g81

Hydrolase/hydrolase inhibitor

PDB id: 2g81

Contents

Protein chains

223 a.a. *

56 a.a. *

Ligands

SO4 ×4

PGE

EDO

ACY ×2

P6G

Metals

_CA

Waters ×323

* Residue conservation analysis

PDB id:

2g81

Name:

Hydrolase/hydrolase inhibitor

Title:

Crystal structure of the bowman-birk inhibitor from vigna unguiculata seeds in complex with beta-trypsin at 1.55 angstrons resolution

Structure:

Cationic trypsin. Chain: e. Synonym: beta-trypsin. Bowman-birk type seed trypsin and chymotrypsin inhibitor. Chain: i. Synonym: btci

Source:

Bos taurus. Cattle. Organism_taxid: 9913. Vigna unguiculata. Cowpea. Organism_taxid: 3917

Resolution:

1.55Å R-factor: 0.155 R-free: 0.169

Authors:

S.M.Freitas,J.A.R.G.Barbosa,L.S.Paulino,R.C.L.Teles,G.F.Esteves, M.M.Ventura

Key ref:

J.A.Barbosa et al. (2007). Crystal structure of the Bowman-Birk Inhibitor from Vigna unguiculata seeds in complex with beta-trypsin at 1.55 A resolution and its structural properties in association with proteinases. Biophys J, 92, 1638-1650. PubMed id: 17142290

Date:

01-Mar-06 Release date: 02-Jan-07

Protein chain

P00760  (TRY1_BOVIN) -  Serine protease 1 from Bos taurus

Seq: 246 a.a.

Struc: 223 a.a.

Protein chain

Q9S9H8  (Q9S9H8_VIGUN) -  Serine protease ISO-inhibitor FIV (Fragment) from Vigna unguiculata

Seq: 78 a.a.

Struc: 56 a.a.*

* PDB and UniProt seqs differ at 2 residue positions (black crosses)

Enzyme reactions

• Enzyme class: Chain E: E.C.3.4.21.4 - trypsin.
• Reaction: Preferential cleavage: Arg-|-Xaa, Lys-|-Xaa.

Biophys J 92:1638-1650 (2007)

PubMed id: 17142290

Crystal structure of the Bowman-Birk Inhibitor from Vigna unguiculata seeds in complex with beta-trypsin at 1.55 A resolution and its structural properties in association with proteinases.

J.A.Barbosa, L.P.Silva, R.C.Teles, G.F.Esteves, R.B.Azevedo, M.M.Ventura, S.M.de Freitas.

ABSTRACT

The structure of the Bowman-Birk inhibitor from Vigna unguiculata seeds (BTCI) in complex with beta-trypsin was solved and refined at 1.55 A to a crystallographic R(factor) of 0.154 and R(free) of 0.169, and represents the highest resolution for a Bowman-Birk inhibitor structure to date. The BTCI-trypsin interface is stabilized by hydrophobic contacts and hydrogen bonds, involving two waters and a polyethylene glycol molecule. The conformational rigidity of the reactive loop is characteristic of the specificity against trypsin, while hydrophobicity and conformational mobility of the antichymotryptic subdomain confer the self-association tendency, indicated by atomic force microscopy, of BTCI in complex and free form. When BTCI is in binary complexes, no significant differences in inhibition constants for producing a ternary complex with trypsin and chymotrypsin were detected. These results indicate that binary complexes present no conformational change in their reactive site for both enzymes confirming that these sites are structurally independent. The free chymotrypsin observed in the atomic force microscopy assays, when the ternary complex is obtained from BTCI-trypsin binary complex and chymotrypsin, could be related more to the self-association tendency between chymotrypsin molecules and the flexibility of the reactive site for this enzyme than to binding-related conformational changes.