title: Three-dimensional structure of phenylalanyl-transfer RNA synthetase from Thermus thermophilus HB8 at 0.6-nm resolution.
abstract: The three-dimensional structure of the heterodimeric alpha 2 beta 2 enzyme phenylalanyl-tRNA synthetase from Thermus thermophilus HB8 has been determined by X-ray crystallography, using the multiple-isomorphous-replacement method at 0.6 nm resolution. Trigonal crystals of space group P3(2)21 have cell dimensions a = b = 17.6 nm and c = 14.2 nm. Assuming one heterodimeric molecule/asymmetric unit, the ratio of unit cell volume/molecular mass was V = 0.00244 nm3/Da, which is in the middle of the range normally observed. However, after a rotation-function calculation and measurement of the density of the native crystals, we postulate the existence of only the alpha beta dimer in the asymmetric units. This implies 73% solvent content in the unit cell. Three heavy-atom derivatives [K2PtCl4, KAu(CN)2 and Hg(CH3COO)2] and the solvent-flattening procedure were used for electron-density-map calculations. This map confirmed our hypothesis and revealed a remarkably large space filled by solvent, with alpha beta dimer only in the asymmetric unit. The phenylalanyl-tRNA synthetase from T. thermophilus molecule has a 'quasi-linear' subunit organization. As can be concluded at this level of resolution, there is no contact between small alpha subunits in the functional heterodimer.
authors.affiliation: Institute of Molecular Biology, Academy of Sciences of the USSR, Moscow.
authors.forename: L
authors.initials: L
authors.lastname: Reshetnikova
authors.forename: M
authors.initials: M
authors.lastname: Chernaya
authors.forename: V
authors.initials: V
authors.lastname: Ankilova
authors.forename: O
authors.initials: O
authors.lastname: Lavrik
authors.forename: M
authors.initials: M
authors.lastname: Delarue
authors.forename: J C
authors.initials: JC
authors.lastname: Thierry
authors.forename: D
authors.initials: D
authors.lastname: Moras
authors.forename: M
authors.initials: M
authors.lastname: Safro
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003460:Crystallization; D005583:Fourier Analysis; D046911:Macromolecular Substances; D015394:Molecular Structure; D008970:Molecular Weight; D010652:Phenylalanine-tRNA Ligase / Q000737:chemistry*; D016963:Thermus thermophilus / Q000235:genetics*; D014961:X-Ray Diffraction
chemical_list: D046911:Macromolecular Substances; D010652:Phenylalanine-tRNA Ligase