Crystal structure of archaeosine tRNA-guanine transglycosylase

J Mol Biol. 2002 May 3;318(3):665-77. doi: 10.1016/S0022-2836(02)00090-6.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Catalytic Domain
  • Crystallography, X-Ray
  • Dimerization
  • Guanine / analogs & derivatives*
  • Guanine / biosynthesis
  • Models, Molecular
  • Molecular Sequence Data
  • Nucleoside Q / biosynthesis
  • Pentosyltransferases / chemistry*
  • Pentosyltransferases / genetics
  • Pentosyltransferases / metabolism
  • Protein Conformation
  • Protein Structure, Quaternary
  • Protein Structure, Tertiary
  • Pyrococcus / enzymology
  • Pyrococcus / genetics
  • Sequence Homology, Amino Acid
  • Static Electricity


  • Nucleoside Q
  • Guanine
  • Pentosyltransferases
  • queuine tRNA-ribosyltransferase
  • 7-deazaguanine

Associated data

  • PDB/1IQ8
  • PDB/1IT7
  • PDB/1IT8