PDBsum entry 1bzx

Hydrolase/hydrolase inhibitor

PDB id: 1bzx

Contents

Protein chains

222 a.a. *

58 a.a. *

Metals

_CA

Waters ×85

* Residue conservation analysis

PDB id:

1bzx

Name:

Hydrolase/hydrolase inhibitor

Title:

The crystal structure of anionic salmon trypsin in complex with bovine pancreatic trypsin inhibitor

Structure:

Protein (trypsin). Chain: e. Protein (bovine pancreatic trypsin inhibitor). Chain: i

Source:

Salmo salar. Atlantic salmon. Organism_taxid: 8030. Bos taurus. Cattle. Organism_taxid: 9913

Biol. unit:

Tetramer (from PQS)

Resolution:

2.10Å R-factor: 0.206 R-free: 0.238

Authors:

R.Helland,I.Leiros,G.I.Berglund,N.P.Willassen,A.O.Smalas

Key ref:

R.Helland et al. (1998). The crystal structure of anionic salmon trypsin in complex with bovine pancreatic trypsin inhibitor. Eur J Biochem, 256, 317-324. PubMed id: 9760170 DOI: 10.1046/j.1432-1327.1998.2560317.x

Date:

05-Nov-98 Release date: 11-Nov-98

Protein chain

P35031  (TRY1_SALSA) -  Trypsin-1 from Salmo salar

Seq: 242 a.a.

Struc: 222 a.a.*

Protein chain

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

DOI no: 10.1046/j.1432-1327.1998.2560317.x

Eur J Biochem 256:317-324 (1998)

PubMed id: 9760170

The crystal structure of anionic salmon trypsin in complex with bovine pancreatic trypsin inhibitor.

R.Helland, I.Leiros, G.I.Berglund, N.P.Willassen, A.O.Smalås.

ABSTRACT

The complex formed between anionic salmon trypsin (ST) and bovine pancreatic trypsin inhibitor (BPTI) has been crystallised, and the X-ray structure has been solved using the molecular replacement method. The crystals are hexagonal and belong to space group P6(1)22 with lattice parameters of a = b = 83.12 A and c = 222.15 A. Data have been collected to 2.1 A and the structure has been refined to a crystallographic R-factor of 20.6%. Catalysis by salmon trypsin is distinguished by a Km value 20-fold lower than that for mammalian trypsins, and a k(cat) twice as high. The present ST-BPTI complex serves as a model for the Michaelis-Menten complex, and has been compared with corresponding bovine and rat trypsin (RT) complexes. The binding of BPTI to salmon trypsin is characterised by stronger primary interactions in the active site, and a somewhat looser secondary binding.

Selected figure(s)

Figure 3.
Fig. 3. Primary and secondary binding. Stereo plot of the primary and secondary binding of the BPTI (blue) to anionic salmon trypsin (red). The N # atom of P1 lysine contacts the carboxylate group of Asp189 through one direct hydrogen bond to O #2 and through a water molecule to O #1 . Five hydrogen bonds, which all contact the inhibitor main chain, are conserved in the secondary binding sites of all three complexes. Two are on the N­ terminal side of the scissile bond, and three on the C­terminal side. Additional hydrogen bonds are formed between inhibitor side chains and the enyme (see Table 4 for further details). The figure was prepared using BOBSCRIPT [33, 34].

Figure 5.
Fig. 5. Electrostatic surface potentials of trypsins. Electrostatic potential of the surfaces of salmon (left), bovine (middle) and rat (right) trypsins. Potentials are taken from the PDB files. The P3­P4¢ binding loops of BPTI illustrates the binding of Lys15I in the specificity pockets and the different orientations of the Arg17I side chain (to the right). The figure also shows that the binding cleft of salmon trypsin is more open than for the mammalian enzymes due to the different fold of the autolysis loop. The figure was prepared using GRASP [37].

The above figures are reprinted by permission from the Federation of European Biochemical Societies: Eur J Biochem (1998, 256, 317-324) copyright 1998.

Figures were selected by an automated process.