PDBsum entry: 1k32

Hydrolase

PDB id: 1k32

Contents

Protein chains

(+ 0 more) 1023 a.a. *

Waters ×2394

* Residue conservation analysis

PDB id:

1k32

Name:

Hydrolase

Title:

Crystal structure of the tricorn protease

Structure:

Tricorn protease. Chain: a, b, c, d, e, f. Engineered: yes

Source:

Thermoplasma acidophilum. Organism_taxid: 2303. Gene: ta1490. Expressed in: escherichia coli bl21(de3). Expression_system_taxid: 469008.

Biol. unit:

Hexamer (from PQS)

Resolution:

2.00Å R-factor: 0.245 R-free: 0.264

Authors:

H.Brandstetter,J.-S.Kim,M.Groll,R.Huber

Key ref:

H.Brandstetter et al. (2001). Crystal structure of the tricorn protease reveals a protein disassembly line. Nature, 414, 466-470. PubMed id: 11719810 DOI: 10.1038/35106609

Date:

01-Oct-01 Release date: 05-Dec-01

Protein chains

P96086  (TRI_THEAC) -  Tricorn protease

Seq: 1071 a.a.

Struc: 1023 a.a.

 Gene Ontology (GO) functional annotation 

• Cellular component: cytoplasm (1 term)
• Biological process: proteolysis (1 term)
• Biochemical function: protein binding (6 terms)

DOI no: 10.1038/35106609

Nature 414:466-470 (2001)

PubMed id: 11719810

Crystal structure of the tricorn protease reveals a protein disassembly line.

H.Brandstetter, J.S.Kim, M.Groll, R.Huber.

ABSTRACT

The degradation of cytosolic proteins is carried out predominantly by the proteasome, which generates peptides of 7-9 amino acids long. These products need further processing. Recently, a proteolytic system was identified in the model organism Thermoplasma acidophilum that performs this processing. The hexameric core protein of this modular system, referred to as tricorn protease, is a 720K protease that is able to assemble further into a giant icosahedral capsid, as determined by electron microscopy. Here, we present the crystal structure of the tricorn protease at 2.0 A resolution. The structure reveals a complex mosaic protein whereby five domains combine to form one of six subunits, which further assemble to form the 3-2-symmetric core protein. The structure shows how the individual domains coordinate the specific steps of substrate processing, including channelling of the substrate to, and the product from, the catalytic site. Moreover, the structure shows how accessory protein components might contribute to an even more complex protein machinery that efficiently collects the tricorn-released products.

Selected figure(s)

Figure 1.
Figure 1: Structure of tricorn protease. a, Ribbon representation of tricorn protease viewed along the molecular three-fold axis. Individual subunits are distinguished by colour. The overall dimensions of the molecule are 160 Å within the plane normal to the three-fold axis and 88 Å parallel to it. The conically shaped central pore measures 45 Å in diameter at its entrance and 20 Å close to the centre of the molecule. All figures were prepared with the programs Molscript and Raster3D^18,19. b, Representation of the highlighted subunit of a using identical colour coding and a similar orientation. The residues forming the propeller lids are displayed as well as the catalytic residues H746 (C1, magenta) and S965 (C2, green). D936, positioned on the C2 domain, confers specificity for basic substrate residues in the active site of the diad-related subunit (compare with a).

Figure 2.
Figure 2: The active site of tricorn protease. a, Surface representation of the active site, colour coded according to its electrostatic potential. The 'cut-open' surface (green) indicates an overall acidic S1 site (red), highly basic S2'/S3' substrate-recognition sites (deep blue), and a slightly positive S4/S5 site. b, The surface charge distributions related to A2:D936 (provided by the diad-related subunit) and D966 (S1); R131 and R132 (S2'/S3'); and A2:R940 and K992 (S4/S5). The unprimed substrate residues (Phe-Lys) correspond to those experimentally determined from a TLCK complex. The primed residues (Arg-Gln-Tyr-O-) were modelled semi-empirically by fitting the solvent electron density in addition to energetic considerations, because solvent molecules are known to mimic substrate-binding sites20.

The above figures are reprinted by permission from Macmillan Publishers Ltd: Nature (2001, 414, 466-470) copyright 2001.