Adenain

 

Human adenovirus proteinase is a cysteine proteinase required for the synthesis of infectious virus. Cofactors discovered include viral DNA, or a short oligopeptide which the enzyme itself cleaves out. The enzyme cleaves specific Gly-Ala peptides in a number of viral precursor proteins, and also cleaves host cell cytoskeleton keratins. The structure and mechanism of this enzyme suggest convergent evolution to give a catalytic mechanism similar to papain.

 

Reference Protein and Structure

Sequences
P03252 UniProt (3.4.22.39)
P03274 UniProt IPR000855 (Sequence Homologues) (PDB Homologues)
Biological species
Human adenovirus 2 (Virus) Uniprot
PDB
1nln - CRYSTAL STRUCTURE OF HUMAN ADENOVIRUS 2 PROTEINASE WITH ITS 11 AMINO ACID COFACTOR AT 1.6 ANGSTROM RESOLUTION (1.6 Å) PDBe PDBsum 1nln
Catalytic CATH Domains
3.40.395.10 CATHdb (see all for 1nln)
Click To Show Structure

Enzyme Reaction (EC:3.4.22.39)

water
CHEBI:15377ChEBI
+
dipeptide zwitterion
CHEBI:90799ChEBI
→
L-alpha-amino acid zwitterion
CHEBI:59869ChEBI

Enzyme Mechanism

Introduction

This enzyme has a virtually identical mechanism to the cysteine proteinase papain. The pKa of the thiol residue of Cys 122 is lowered by the action of His 54 as a general base catalyst which abstracts the cysteine proton. This allows the thiolate ion to acts as a nucleophile in attack of the carbonyl carbon. The tetrahedral transition state is stabilised by the oxyanion hole formed by Gln 115. Glu 71 activates His 54, which is able to act as a general acid catalyst in protonating the leaving group to facilitate cleavage of the scissile bond. His 54 then activates water by proton abstraction to cleave the acyl-enzyme intermediate.

Catalytic Residues Roles

UniProt PDB* (1nln)
His54 His54A Acts as a general acid/base catalyst to activate the Cys 122 and water for nucleophilic attack, and to facilitate collapse of the intermediate towards cleavage of the scissile bond. proton acceptor, proton donor
Glu71 Glu71A Activates His 54. electrostatic stabiliser
Cys122 (main-N), Gln115 Cys122A (main-N), Gln115A Forms the oxyanion hole which functions to stabilise the negative charge that accumulates on the carbonyl oxygen of the substrate during the reaction. electrostatic stabiliser
Cys122 Cys122A Acts as a nucleophile to attack the carbonyl carbon of the substrate. nucleofuge, nucleophile, proton acceptor, proton donor
*PDB label guide - RESx(y)B(C) - RES: Residue Name; x: Residue ID in PDB file; y: Residue ID in PDB sequence if different from PDB file; B: PDB Chain; C: Biological Assembly Chain if different from PDB. If label is "Not Found" it means this residue is not found in the reference PDB.

Chemical Components

proton transfer, bimolecular nucleophilic addition, intermediate formation, overall reactant used, unimolecular elimination by the conjugate base, intermediate collapse, overall product formed, native state of enzyme regenerated

References

  1. McGrath WJ et al. (2003), Biochim Biophys Acta, 1648, 1-11. Crystallographic structure at 1.6-Å resolution of the human adenovirus proteinase in a covalent complex with its 11-amino-acid peptide cofactor: insights on a new fold. DOI:10.1016/s1570-9639(03)00024-4. PMID:12758141.
  2. Baniecki ML et al. (2013), J Biol Chem, 288, 2081-2091. Regulation of a viral proteinase by a peptide and DNA in one-dimensional space: III. atomic resolution structure of the nascent form of the adenovirus proteinase. DOI:10.1074/jbc.M112.407429. PMID:23043139.
  3. Ding J et al. (1996), EMBO J, 15, 1778-1783. Crystal structure of the human adenovirus proteinase with its 11 amino acid cofactor. DOI:10.2210/pdb1avp/pdb. PMID:8617222.
  4. Grierson AW et al. (1994), J Gen Virol, 75, 2761-2764. The protease of adenovirus serotype 2 requires cysteine residues for both activation and catalysis. DOI:10.1099/0022-1317-75-10-2761. PMID:7931163.

Step 1. His54 deprotonate Cys122 activating it so that it can attack the carbon of the peptide bond in a nucleophilic addition.

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Catalytic Residues Roles

Residue Roles
Glu71A electrostatic stabiliser
Gln115A electrostatic stabiliser
Cys122A (main-N) electrostatic stabiliser
Cys122A proton donor
His54A proton acceptor
Cys122A nucleophile

Chemical Components

proton transfer, ingold: bimolecular nucleophilic addition, intermediate formation, overall reactant used

Step 2. The oxyanion initiates an elimination resulting in the cleavage of the peptide bond. The N-terminal product then accepts a proton from His54 which prevents reformation of the peptide bond.

Download: Image, Marvin File

Catalytic Residues Roles

Residue Roles
Glu71A electrostatic stabiliser
Gln115A electrostatic stabiliser
Cys122A (main-N) electrostatic stabiliser
His54A proton donor

Chemical Components

proton transfer, ingold: unimolecular elimination by the conjugate base, intermediate collapse, overall product formed

Step 3. His54 deprotonates water activating it so that it can attack the carbon of the thioester bond in a nucleophilic addition.

Download: Image, Marvin File

Catalytic Residues Roles

Residue Roles
Glu71A electrostatic stabiliser
Gln115A electrostatic stabiliser
Cys122A (main-N) electrostatic stabiliser
His54A proton acceptor

Chemical Components

proton transfer, ingold: bimolecular nucleophilic addition, overall reactant used, intermediate formation

Step 4. The oxyanion initiates another elimination resulting in the cleavage of the thioester bond. The released Cys122 accepts a proton from His54 which returns the enzyme to its native state.

Download: Image, Marvin File

Catalytic Residues Roles

Residue Roles
Glu71A electrostatic stabiliser
Gln115A electrostatic stabiliser
Cys122A (main-N) electrostatic stabiliser
His54A proton donor
Cys122A proton acceptor, nucleofuge

Chemical Components

ingold: unimolecular elimination by the conjugate base, proton transfer, intermediate collapse, overall product formed, native state of enzyme regenerated
Download: Image, Marvin File

Step 1. His54 deprotonate Cys122 activating it so that it can attack the carbon of the peptide bond in a nucleophilic addition.

Step 2. The oxyanion initiates an elimination resulting in the cleavage of the peptide bond. The N-terminal product then accepts a proton from His54 which prevents reformation of the peptide bond.

Step 3. His54 deprotonates water activating it so that it can attack the carbon of the thioester bond in a nucleophilic addition.

Step 4. The oxyanion initiates another elimination resulting in the cleavage of the thioester bond. The released Cys122 accepts a proton from His54 which returns the enzyme to its native state.

Products.

Contributors

Gary McDowell, Gemma L. Holliday, Charity Hornby