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Catalytic Site Atlas

CSA LITERATURE entry for 1k32

E.C. nameTRICORN PROTEASE
SpeciesThermoplasma acidophilum ()
E.C. Number (IntEnz) 3.4.21.-
CSA Homologues of 1k321n6d,1n6e,1n6f,
CSA Entries With UniProtID
CSA Entries With EC Number 3.4.21.-
PDBe Entry 1k32
PDBSum Entry 1k32
MACiE Entry 1k32

Literature Report

IntroductionThe tricorn protease is the core of a proteolytic system identified in the model organism Thermoplasma acidophilum. This complex functions to degrade the 7-9 residue peptides that are produced by the proteasome-mediated degradation of cellular proteins. The basic functional unit of the tricorn protease is a homohexamer of the 121 kDa subunit; however electron microscopy studies indicate that 20 copies of this 720 kDa hexamer can assemble further in vivo to form a giant 14.6 MDa icosahedral capsid.
MechansimThe tricorn protease is thought to use a mechanism similar to that of the trypsin-like serine proteases. His 746 deprotonates Ser 965 which attacks the peptide bond to form a tetrahedral intermediate. Accumulation of negative charge on the carbonyl oxygen during formation of the tetrahedral intermediate is stabilised by an oxyanion hole composed of the backbone NH groups of Gly 918 and Asp 966. Collapse of the tetrahedral intermediate with protonation of the departing leaving group by His 746 generates and acyl-enzyme intermediate; this is subsequently hydrolysed by a water molecule that is deprotonated by His 746.

Catalytic Sites for 1k32

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
SerA965965macie:sideChainActs as a nucleophile to attack the peptide bond and form an acyl-enzyme intermediate which is subsequently hydrolysed.
HisA746746macie:sideChainDeprotonates Ser 965. Protonates the departing amine nitrogen during collapse of the tetrahedral intermediate. Deprotonates the water molecule that hydrolyses the acyl-enzyme intermediate.
AspA966966macie:mainChainAmideBackbone NH forms part of the oxyanion hole that stabilises the tetrahedral intermediate.
GlyA918918macie:mainChainAmideBackbone NH forms part of the oxyanion hole that stabilises the tetrahedral intermediate.

Annotated By Reference To The Literature - Site 2 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
SerB965965macie:sideChainActs as a nucleophile to attack the peptide bond and form an acyl-enzyme intermediate which is subsequently hydrolysed.
HisB746746macie:sideChainDeprotonates Ser 965. Protonates the departing amine nitrogen during collapse of the tetrahedral intermediate. Deprotonates the water molecule that hydrolyses the acyl-enzyme intermediate.
AspB966966macie:mainChainAmideBackbone NH forms part of the oxyanion hole that stabilises the tetrahedral intermediate.
GlyB918918macie:mainChainAmideBackbone NH forms part of the oxyanion hole that stabilises the tetrahedral intermediate.

Annotated By Reference To The Literature - Site 3 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
SerC965965macie:sideChainActs as a nucleophile to attack the peptide bond and form an acyl-enzyme intermediate which is subsequently hydrolysed.
HisC746746macie:sideChainDeprotonates Ser 965. Protonates the departing amine nitrogen during collapse of the tetrahedral intermediate. Deprotonates the water molecule that hydrolyses the acyl-enzyme intermediate.
AspC966966macie:mainChainAmideBackbone NH forms part of the oxyanion hole that stabilises the tetrahedral intermediate.
GlyC918918macie:mainChainAmideBackbone NH forms part of the oxyanion hole that stabilises the tetrahedral intermediate.

Annotated By Reference To The Literature - Site 4 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
SerD965965macie:sideChainActs as a nucleophile to attack the peptide bond and form an acyl-enzyme intermediate which is subsequently hydrolysed.
HisD746746macie:sideChainDeprotonates Ser 965. Protonates the departing amine nitrogen during collapse of the tetrahedral intermediate. Deprotonates the water molecule that hydrolyses the acyl-enzyme intermediate.
AspD966966macie:mainChainAmideBackbone NH forms part of the oxyanion hole that stabilises the tetrahedral intermediate.
GlyD918918macie:mainChainAmideBackbone NH forms part of the oxyanion hole that stabilises the tetrahedral intermediate.

Annotated By Reference To The Literature - Site 5 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
SerE965965macie:sideChainActs as a nucleophile to attack the peptide bond and form an acyl-enzyme intermediate which is subsequently hydrolysed.
HisE746746macie:sideChainDeprotonates Ser 965. Protonates the departing amine nitrogen during collapse of the tetrahedral intermediate. Deprotonates the water molecule that hydrolyses the acyl-enzyme intermediate.
AspE966966macie:mainChainAmideBackbone NH forms part of the oxyanion hole that stabilises the tetrahedral intermediate.
GlyE918918macie:mainChainAmideBackbone NH forms part of the oxyanion hole that stabilises the tetrahedral intermediate.

Annotated By Reference To The Literature - Site 6 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
SerF965965macie:sideChainActs as a nucleophile to attack the peptide bond and form an acyl-enzyme intermediate which is subsequently hydrolysed.
HisF746746macie:sideChainDeprotonates Ser 965. Protonates the departing amine nitrogen during collapse of the tetrahedral intermediate. Deprotonates the water molecule that hydrolyses the acyl-enzyme intermediate.
AspF966966macie:mainChainAmideBackbone NH forms part of the oxyanion hole that stabilises the tetrahedral intermediate.
GlyF918918macie:mainChainAmideBackbone NH forms part of the oxyanion hole that stabilises the tetrahedral intermediate.

Literature References

Notes:His 746 is correctly orientated by the O-gamma of Ser 745, which in turn is polarised by Glu 1023.
Brandstetter H
Crystal structure of the tricorn protease reveals a protein disassembly line.
Nature 2001 414 466-470
PubMed: 11719810
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