Crystal structure of a phage Twort group I ribozyme-product complex.
Publication Type:Journal Article
Source:Nat Struct Mol Biol, Volume 12, Issue 1, p.82-9 (2005)
Keywords:Bacteriophages, Base Pairing, Base Sequence, Binding Sites, Catalysis, Crystallography, X-Ray, Guanosine, Introns, Metals, Models, Molecular, Molecular Sequence Data, Nucleic Acid Conformation, Phosphates, RNA, Catalytic
<p>Group I introns are catalytic RNAs capable of orchestrating two sequential phosphotransesterification reactions that result in self-splicing. To understand how the group I intron active site facilitates catalysis, we have solved the structure of an active ribozyme derived from the orf142-I2 intron from phage Twort bound to a four-nucleotide product RNA at a resolution of 3.6 A. In addition to the three conserved domains characteristic of all group I introns, the Twort ribozyme has peripheral insertions characteristic of phage introns. These elements form a ring that completely envelops the active site, where a snug pocket for guanosine is formed by a series of stacked base triples. The structure of the active site reveals three potential binding sites for catalytic metals, and invokes a role for the 2' hydroxyl of the guanosine substrate in organization of the active site for catalysis.</p>