Acta Crystallographica Section F

Structural Biology and Crystallization Communications

Volume 61, Part 10 (October 2005)

crystallization communications

Acta Cryst. (2005). F61, 945-948 [ doi:10.1107/S1744309105029246 ]

Crystallization and preliminary X-ray characterization of the nitrile reductase QueF: a queuosine-biosynthesis enzyme

M. A. Swairjo, R. R. Reddy, B. Lee, S. G. Van Lanen, S. Brown, V. de Crécy-Lagard, D. Iwata-Reuyl and P. Schimmel

Abstract: QueF (MW = 19.4 kDa) is a recently characterized nitrile oxidoreductase which catalyzes the NADPH-dependent reduction of 7-cyano-7-deazaguanine (preQ₀) to 7-aminomethyl-7-deazaguanine, a late step in the biosynthesis of the modified tRNA nucleoside queuosine. Initial crystals of homododecameric Bacillus subtilis QueF diffracted poorly to 8.0 Å. A three-dimensional model based on homology with the tunnel-fold enzyme GTP cyclohydrolase I suggested catalysis at intersubunit interfaces and a potential role for substrate binding in quaternary structure stabilization. Guided by this insight, a second crystal form was grown that was strictly dependent on the presence of preQ₀. This crystal form diffracted to 2.25 Å resolution.

Keywords: bioinformatics; YkvM; YqcD; RNA; post-transcriptional modification.