1iq8

File:1iq8.jpg

spinqualitylabelsall models 1iq8, resolution 2.2Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Crystal Structure of archaeosine tRNA-guanine transglycosylase from Pyrococcus horikoshii

OverviewOverview

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 StructureAbout this Structure

1IQ8 is a Single protein structure of sequence from Pyrococcus horikoshii with and as ligands. Active as Queuine tRNA-ribosyltransferase, with EC number 2.4.2.29 Full crystallographic information is available from OCA.

ReferenceReference

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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