title: Crystallization and preliminary X-ray crystallographic analysis of Aquifex aeolicus SelA, a bacterial selenocysteine synthase.
abstract: Selenocysteine (Sec), the 21st amino acid, is synthesized on its specific tRNA (tRNA(Sec)) via a multi-step process. In bacteria, tRNA(Sec) is ligated first with serine by seryl-tRNA synthetase, which is followed by Ser-to-Sec conversion by Sec synthase (SelA). To elucidate its structure and catalytic mechanism, Aquifex aeolicus SelA was crystallized. Although wild-type SelA crystals diffracted X-rays poorly (to up to 8 Å resolution), the resolution was improved by introducing a quadruple point mutation targeting the loop regions and by methylating the lysine residues, which yielded 3.9 Å resolution diffraction data from a full-length SelA crystal. Truncation of the N-terminal region (ΔN) also improved the resolution. A 3.3 Å resolution data set for phase determination was obtained from a crystal of selenomethionine-substituted Lys-methylated SelA-ΔN.
authors.affiliation: Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan.
authors.forename: Yuzuru
authors.initials: Y
authors.lastname: Itoh
authors.forename: Shun-ichi
authors.initials: S
authors.lastname: Sekine
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Yokoyama
mesh_terms: D001419:Bacteria / Q000201:enzymology*; D003460:Crystallization; D018360:Crystallography, X-Ray; D008745:Methylation; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D014166:Transferases / Q000737:chemistry*
chemical_list: D014166:Transferases; C060600:selenium transferase