title: Crystal structure of the apo forms of psi 55 tRNA pseudouridine synthase from Mycobacterium tuberculosis: a hinge at the base of the catalytic cleft.
abstract: The three-dimensional structure of the RNA-modifying enzyme, psi55 tRNA pseudouridine synthase from Mycobacterium tuberculosis, is reported. The 1.9-A resolution crystal structure reveals the enzyme, free of substrate, in two distinct conformations. The structure depicts an interesting mode of protein flexibility involving a hinged bending in the central beta-sheet of the catalytic module. Key parts of the active site cleft are also found to be disordered in the substrate-free form of the enzyme. The hinge bending appears to act as a clamp to position the substrate. Our structural data furthers the previously proposed mechanism of tRNA recognition. The present crystal structure emphasizes the significant role that protein dynamics must play in tRNA recognition, base flipping, and modification.
authors.affiliation: UCLA-Department of Energy Institute for Genomics and Proteomics, Los Angeles, California 90095, USA.
authors.forename: Barnali N
authors.initials: BN
authors.lastname: Chaudhuri
authors.forename: Sum
authors.initials: S
authors.lastname: Chan
authors.forename: L Jeanne
authors.initials: LJ
authors.lastname: Perry
authors.forename: Todd O
authors.initials: TO
authors.lastname: Yeates
mesh_terms: D001665:Binding Sites; D020134:Catalytic Domain; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D019753:Intramolecular Lyases / Q000737:chemistry*; D019751:Intramolecular Transferases; D008954:Models, Biological; D008958:Models, Molecular; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012313:RNA / Q000737:chemistry
chemical_list: D012313:RNA; D019751:Intramolecular Transferases; C096995:pseudouridine synthases; D019753:Intramolecular Lyases