PDBsum entry 1t7c

Hydrolase/hydrolase inhibitor

PDB id: 1t7c

Contents

Protein chains

239 a.a. *

58 a.a. *

Ligands

SO4 ×9

Waters ×518

* Residue conservation analysis

PDB id:

1t7c

Name:

Hydrolase/hydrolase inhibitor

Title:

Crystal structure of the p1 glu bpti mutant- bovine chymotrypsin complex

Structure:

Chymotrypsin a. Chain: a, c. Pancreatic trypsin inhibitor. Chain: b, d. Synonym: basic protease inhibitor, bpi, bpti, aprotinin. Engineered: yes. Mutation: yes

Source:

Bos taurus. Cattle. Organism_taxid: 9913. Expressed in: escherichia coli bl21(de3). Expression_system_taxid: 469008.

Biol. unit:

Dimer (from PQS)

Resolution:

1.85Å R-factor: 0.194 R-free: 0.218

Authors:

H.Czapinska,R.Helland,J.Otlewski,A.O.Smalas

Key ref:

H.Czapinska et al. (2004). Crystal structures of five bovine chymotrypsin complexes with P1 BPTI variants. J Mol Biol, 344, 1005-1020. PubMed id: 15544809 DOI: 10.1016/j.jmb.2004.09.088

Date:

09-May-04 Release date: 08-Mar-05

Protein chains

P00766  (CTRA_BOVIN) -  Chymotrypsinogen A from Bos taurus

Seq: 245 a.a.

Struc: 239 a.a.

Protein chains

P00974  (BPT1_BOVIN) -  Pancreatic trypsin inhibitor from Bos taurus

Seq: 100 a.a.

Struc: 58 a.a.*

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

Enzyme reactions

• Enzyme class: Chains A, C: E.C.3.4.21.1 - chymotrypsin.
• Reaction: Preferential cleavage: Tyr-|-Xaa, Trp-|-Xaa, Phe-|-Xaa, Leu-|-Xaa.

DOI no: 10.1016/j.jmb.2004.09.088

J Mol Biol 344:1005-1020 (2004)

PubMed id: 15544809

Crystal structures of five bovine chymotrypsin complexes with P1 BPTI variants.

H.Czapinska, R.Helland, A.O.Smalås, J.Otlewski.

ABSTRACT

The bovine chymotrypsin-bovine pancreatic trypsin inhibitor (BPTI) interaction belongs to extensively studied models of protein-protein recognition. The accommodation of the inhibitor P1 residue in the S1 binding site of the enzyme forms the hot spot of this interaction. Mutations introduced at the P1 position of BPTI result in a more than five orders of magnitude difference of the association constant values with the protease. To elucidate the structural aspects of the discrimination between different P1 residues, crystal structures of five bovine chymotrypsin-P1 BPTI variant complexes have been determined at pH 7.8 to a resolution below 2 A. The set includes polar (Thr), ionizable (Glu, His), medium-sized aliphatic (Met) and large aromatic (Trp) P1 residues and complements our earlier studies of the interaction of different P1 side-chains with the S1 pocket of chymotrypsin. The structures have been compared to the complexes of proteases with similar and dissimilar P1 preferences, including Streptomyces griseus proteases B and E, human neutrophil elastase, crab collagenase, bovine trypsin and human thrombin. The S1 sites of these enzymes share a common general shape of significant rigidity. Large and branched P1 residues adapt in their complexes similar conformations regardless of the polarity and size differences between their S1 pockets. Conversely, long and flexible residues such as P1 Met are present in the disordered form and display a conformational diversity despite similar inhibitory properties with respect to most enzymes studied. Thus, the S1 specificity profiles of the serine proteases appear to result from the precise complementarity of the P1-S1 interface and minor conformational adjustments occurring upon the inhibitor binding.

Selected figure(s)

Figure 1.
Figure 1. The electron density for the P1 residue of BPTI and residues Ser189, Ser190 and Met192 of chymotrypsin together with the hydrogen bonding pattern of the P1 side-chain in the structures of the following complexes: (a) Chtp-K15E BPTI; (b) Chtp-K15M BPTI; (c) Chtp-K15H BPTI; (d) Chtp-K15T BPTI; (e) Chtp-K15W BPTI. The 2F[o] -F[c] maps were contoured at 1.5s. Selected side-chains are indicated in red, the binding loop of the inhibitor in orange and the S1 binding pocket of the enzyme in gray (only the main-chain of the S1 pocket together with Cys191 and Cys220 side-chains is presented for clarity). This and the following Figures were produced with the program XtalView.47

Figure 6.
Figure 6. The superposition of the S1 pockets in P1 Trp BPTI-bovine chymotrypsin complex (red/orange); P1 Trp BPTI-bovine trypsin complex (PDB 3BTW, blue); and the complex of thrombin with the P1 Trp possessing peptidyl inhibitor (PDB 1AD8, green).

The above figures are reprinted by permission from Elsevier: J Mol Biol (2004, 344, 1005-1020) copyright 2004.

Figures were selected by an automated process.