4CKB: Vaccinia Virus Capping Enzyme Complexed With Gtp And Sah

Vaccinia virus capping enzyme is a heterodimer of D1 (844 aa) and D12 (287 aa) polypeptides that executes all three steps in m(7)GpppRNA synthesis. The D1 subunit comprises an N-terminal RNA triphosphatase (TPase)-guanylyltransferase (GTase) module and a C-terminal guanine-N7-methyltransferase (MTase) module. The D12 subunit binds and allosterically stimulates the MTase module. Crystal structures of the complete D1D12 heterodimer disclose the TPase and GTase as members of the triphosphate tunnel metalloenzyme and covalent nucleotidyltransferase superfamilies, respectively, albeit with distinctive active site features. An extensive TPase-GTase interface clamps the GTase nucleotidyltransferase and OB-fold domains in a closed conformation around GTP. Mutagenesis confirms the importance of the TPase-GTase interface for GTase activity. The D1D12 structure complements and rationalizes four decades of biochemical studies of this enzyme, which was the first capping enzyme to be purified and characterized, and provides new insights into the origins of the capping systems of other large DNA viruses.
PDB ID: 4CKBDownload
MMDB ID: 118373
PDB Deposition Date: 2014/1/2
Updated in MMDB: 2014/03
Experimental Method:
x-ray diffraction
Resolution: 2.8  Å
Source Organism:
Similar Structures:
Biological Unit for 4CKB: dimeric; determined by author and by software (PISA)
Molecular Components in 4CKB
Label Count Molecule
Proteins (2 molecules)
mRNA-capping Enzyme Catalytic Subunit(Gene symbol: D1R)
Molecule annotation
mRNA-capping Enzyme Regulatory Subunit(Gene symbol: D12L)
Molecule annotation
Chemicals (2 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB