PDBsum entry 1a0j

Serine protease

PDB id: 1a0j

Contents

Protein chains

223 a.a. *

Ligands

SO4 ×10

BEN ×4

Metals

_CA

Waters ×379

* Residue conservation analysis

PDB id:

1a0j

Name:

Serine protease

Title:

Crystal structure of a non-psychrophilic trypsin from a cold-adapted fish species.

Structure:

Trypsin. Chain: a, b, c, d. Other_details: benzamidine inhibitor in the active site. The amino acid numbering scheme used is adopted from chymotrypsinogen.

Source:

Salmo salar. Atlantic salmon. Organism_taxid: 8030. Organ: pancreas

Biol. unit:

Tetramer (from PQS)

Resolution:

1.70Å R-factor: 0.173 R-free: 0.215

Authors:

H.-K.Schroeder,N.P.Willassen,A.O.Smalaas

Key ref:

H.K.Schrøder et al. (1998). Structure of a non-psychrophilic trypsin from a cold-adapted fish species. Acta Crystallogr D Biol Crystallogr, 54, 780-798. PubMed id: 9757092 DOI: 10.1107/S0907444997018611

Date:

01-Dec-97 Release date: 13-Jan-99

Protein chains

P35033  (TRY3_SALSA) -  Trypsin-3 (Fragment) from Salmo salar

Seq: 238 a.a.

Struc: 223 a.a.

Enzyme reactions

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

DOI no: 10.1107/S0907444997018611

Acta Crystallogr D Biol Crystallogr 54:780-798 (1998)

PubMed id: 9757092

Structure of a non-psychrophilic trypsin from a cold-adapted fish species.

H.K.Schrøder, N.P.Willassen, A.O.Smalås.

ABSTRACT

The crystal structure of cationic trypsin (CST) from the Atlantic salmon (Salmo salar) has been refined at 1.70 A resolution. The crystals are orthorhombic, belong to space group P212121, with lattice parameters a = 65.91, b = 83.11 and c = 154.79 A, and comprise four molecules per asymmetric unit. The structure was solved by molecular replacement with AMoRe and refined with X-PLOR to an R value of 17.4% and Rfree of 21.5% for reflections |F| > 3sigmaF between 8.0 and 1.7 A resolution. The four non-crystallographic symmetry (NCS) related molecules in the asymmetric unit display r.m.s. deviations in the range 0.31-0.74 A for main-chain atoms, with the largest differences confined to two loops. One of these is the calcium-binding loop where the electron-density indicates a calcium ion for only one of the four molecules. In order to find structural rationalizations for the observed difference in thermostability and catalytic efficiency of CST, anionic salmon trypsin (AST) and bovine trypsin (BT), the three structures have been extensively compared. The largest deviations for the superimposed structures occur in the surface loops and particularly in the so-called 'autolysis loop'. Both the salmon enzymes possess a high methionine content, lower overall hydrophobicity and enhanced surface hydrophilicity, compared with BT. These properties have so far been correlated to cold-adaptation features, while in this work it is shown that the non-psychrophilic cationic salmon trypsin shares these features with the psychrophilic anionic salmon trypsin.

Selected figure(s)

Figure 5.
Fig. 5. Superposition of the C a atoms of the four independent molecules in the asymmetric unit. Mol A (red) and C (green) are shown in bold lines and Mol B (blue) and D (orange) in broken lines. The two most striking differences amng the four molecules can be seen in the upper right of the molecules (residues 37-41 and 69-79). The three catalytic residues (Aspl02, His57 and Ser195), benzmidine inhibitors and the calcium ion are also included. Every 20th reside is labelled.

Figure 9.
Fig. 9. A aA-weighted 2F o - F c map at 1.3a of the sulfate ion SO4249 of Mol A bound to ArgA156 and ThrA154, and the neighbouring ion pair in Mol A: Glual-His 71. Created by BobScript (Esnouf, 997).

The above figures are reprinted by permission from the IUCr: Acta Crystallogr D Biol Crystallogr (1998, 54, 780-798) copyright 1998.

Figures were selected by an automated process.