1UEV: Divergent Evolutions Of Trinucleotide Polymerization Revealed By An Archaeal Cca-Adding Enzyme Structure

CCA-adding enzyme [ATP(CTP):tRNA nucleotidyltransferase], a template-independent RNA polymerase, adds the defined 'cytidine-cytidine-adenosine' sequence onto the 3' end of tRNA. The archaeal CCA-adding enzyme (class I) and eubacterial/eukaryotic CCA-adding enzyme (class II) show little amino acid sequence homology, but catalyze the same reaction in a defined fashion. Here, we present the crystal structures of the class I archaeal CCA-adding enzyme from Archaeoglobus fulgidus, and its complexes with CTP and ATP at 2.0, 2.0 and 2.7 A resolutions, respectively. The geometry of the catalytic carboxylates and the relative positions of CTP and ATP to a single catalytic site are well conserved in both classes of CCA-adding enzymes, whereas the overall architectures, except for the catalytic core, of the class I and class II CCA-adding enzymes are fundamentally different. Furthermore, the recognition mechanisms of substrate nucleotides and tRNA molecules are distinct between these two classes, suggesting that the catalytic domains of class I and class II enzymes share a common origin, and distinct substrate recognition domains have been appended to form the two presently divergent classes.
PDB ID: 1UEVDownload
MMDB ID: 25497
PDB Deposition Date: 2003/5/21
Updated in MMDB: 2003/12
Experimental Method:
x-ray diffraction
Resolution: 2.7  Å
Source Organism:
Similar Structures:
Biological Unit for 1UEV: monomeric; determined by author
Molecular Components in 1UEV
Label Count Molecule
Protein (1 molecule)
tRNA Nucleotidyltransferase(Gene symbol: AF_RS10845)
Molecule annotation
Chemicals (5 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB