1vfg

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spinqualitylabelsall models 1vfg, resolution 2.8Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Crystal structure of tRNA nucleotidyltransferase complexed with a primer tRNA and an incoming ATP analog

Overview

The 3'-terminal CCA nucleotide sequence (positions 74-76) of transfer RNA is essential for amino acid attachment and interaction with the ribosome during protein synthesis. The CCA sequence is synthesized de novo and/or repaired by a template-independent RNA polymerase, 'CCA-adding enzyme', using CTP and ATP as substrates. Despite structural and biochemical studies, the mechanism by which the CCA-adding enzyme synthesizes the defined sequence without a nucleic acid template remains elusive. Here we present the crystal structure of Aquifex aeolicus CCA-adding enzyme, bound to a primer tRNA lacking the terminal adenosine and an incoming ATP analogue, at 2.8 A resolution. The enzyme enfolds the acceptor T helix of the tRNA molecule. In the catalytic pocket, C75 is adjacent to ATP, and their base moieties are stacked. The complementary pocket for recognizing C74-C75 of tRNA forms a 'protein template' for the penultimate two nucleotides, mimicking the nucleotide template used by template-dependent polymerases. These results are supported by systematic analyses of mutants. Our structure represents the 'pre-insertion' stage of selecting the incoming nucleotide and provides the structural basis for the mechanism underlying template-independent RNA polymerization.

About this Structure

1VFG is a Single protein structure of sequence from Aquifex aeolicus with as ligand. Active as Polynucleotide adenylyltransferase, with EC number 2.7.7.19 Full crystallographic information is available from OCA.

Reference

Structural basis for template-independent RNA polymerization., Tomita K, Fukai S, Ishitani R, Ueda T, Takeuchi N, Vassylyev DG, Nureki O, Nature. 2004 Aug 5;430(7000):700-4. PMID:15295603

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