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spinqualitylabelsall models 1it7, resolution 2.30Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Crystal structure of archaeosine tRNA-guanine transglycosylase complexed with guanine

Overview

Archaeosine tRNA-guanine transglycosylase (ArcTGT) catalyzes the exchange, of guanine at position 15 in the D-loop of archaeal tRNAs with a free, 7-cyano-7-deazaguanine (preQ(0)) base, as the first step in the, biosynthesis of an archaea-specific modified base, archaeosine, (7-formamidino-7-deazaguanosine). We determined the crystal structures of, ArcTGT from Pyrococcus horikoshii at 2.2 A resolution and its complexes, with guanine and preQ(0), at 2.3 and 2.5 A resolutions, respectively. The, N-terminal catalytic domain folds into an (alpha/beta)(8) barrel with a, characteristic zinc-binding site, showing structural similarity with that, of the bacterial queuosine TGT (QueTGT), which is involved in queuosine, (7-[[(4,5-cis-dihydroxy-2-cyclopenten-1-yl)-amino]methyl]-7-deazaguanosine, ) biosynthesis and targets the tRNA anticodon. ArcTGT forms a dimer, involving the zinc-binding site and the ArcTGT-specific C-terminal domain., The C-terminal domains have novel folds, including an OB fold-like "PUA, domain", whose sequence is widely conserved in eukaryotic and archaeal RNA, modification enzymes. Therefore, the C-terminal domains may be involved in, tRNA recognition. In the free-form structure of ArcTGT, an alpha-helix, located at the rim of the (alpha/beta)(8) barrel structure is completely, disordered, while it is ordered in the guanine-bound and preQ(0)-bound, forms. Structural comparison of the ArcTGT.preQ(0), ArcTGT.guanine, and, QueTGT.preQ(1) complexes provides novel insights into the substrate, recognition mechanisms of ArcTGT.

About this Structure

1IT7 is a Single protein structure of sequence from Pyrococcus horikoshii with ZN, MG and GUN as ligands. Active as Queuine tRNA-ribosyltransferase, with EC number 2.4.2.29 Full crystallographic information is available from OCA.

Reference

Crystal structure of archaeosine tRNA-guanine transglycosylase., Ishitani R, Nureki O, Fukai S, Kijimoto T, Nameki N, Watanabe M, Kondo H, Sekine M, Okada N, Nishimura S, Yokoyama S, J Mol Biol. 2002 May 3;318(3):665-77. PMID:12054814

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