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Publication Abstract from PubMed

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.

Divergent evolutions of trinucleotide polymerization revealed by an archaeal CCA-adding enzyme structure.,Okabe M, Tomita K, Ishitani R, Ishii R, Takeuchi N, Arisaka F, Nureki O, Yokoyama S EMBO J. 2003 Nov 3;22(21):5918-27. PMID:14592988^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.