3WFS: Trna Processing Enzyme Complex 3

The 3'-terminal CCA (CCA-3' at positions 74-76) of tRNA is synthesized by CCA-adding enzyme using CTP and ATP as substrates, without a nucleic acid template. In Aquifex aeolicus, CC-adding and A-adding enzymes collaboratively synthesize the CCA-3'. The mechanism of CCA-3' synthesis by these two enzymes remained obscure. We now present crystal structures representing CC addition onto tRNA by A. aeolicus CC-adding enzyme. After C(7)(4) addition in an enclosed active pocket and pyrophosphate release, the tRNA translocates and rotates relative to the enzyme, and C(7)(5) addition occurs in the same active pocket as C(7)(4) addition. At both the C(7)(4)-adding and C(7)(5)-adding stages, CTP is selected by Watson-Crick-like hydrogen bonds between the cytosine of CTP and conserved Asp and Arg residues in the pocket. After C(7)(4)C(7)(5) addition and pyrophosphate release, the tRNA translocates further and drops off the enzyme, and the CC-adding enzyme terminates RNA polymerization.
PDB ID: 3WFSDownload
MMDB ID: 116356
PDB Deposition Date: 2013/7/23
Updated in MMDB: 2014/08
Experimental Method:
x-ray diffraction
Resolution: 3.31  Å
Source Organism:
Thermotoga maritima MSB8
Similar Structures:
Biological Unit for 3WFS: dimeric; determined by author and by software (PISA)
Molecular Components in 3WFS
Label Count Molecule
Protein (1 molecule)
Poly a Polymerase
Molecule annotation
Nucleotide(1 molecule)
RNA (74-mer)
Molecule annotation
Chemicals (2 molecules)
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Citing MMDB