Albany 2015:Book of Abstracts
June 9-13 2015
©Adenine Press (2012)
The crystal structure and catalytic mechanism of the twister ribozyme
The nucleolytic ribozymes are a group of RNA species that undergo self-cleavage or ligation at a particular site. Originally discovered in plant pathogens, these were mostly involved in processing replication intermediates, and later found to be a means of regulating genetic expression in bacteria. However it has recently become clear that ribozyme sequences are in fact very widespread in many genomes, located within non-coding RNA sequences, and are strongly conserved and expressed inside the cell. The twister ribozyme, recently discovered in the Breaker laboratory, is another small nucleolytic ribozyme that is widely disseminated in the genomes of bacteria and eukarya.
We have solved the crystal structure of this ribozyme from Oryza sativa at 2.3 Å resolution (Liu et al, 2014). The RNA adopts a novel compact fold based on a unique reversed, double pseudoknot structure, with the scissile phosphate at its center. All highly-conserved nucleobases form key structural elements including a guanine nucleobase that has its Watson-Crick edge directed towards the scissile phosphate. The pH dependence of the cleavage rate is bell-shaped, consistent with general acid-base catalysis. We have structural and mechanistic evidence for the participation of guanine and adenine nucleobases in proton transfers to the participating O2' and O5' atoms in a mechanism with several novel features.
Y. Liu, T. J. Wilson, S. A. McPhee and D. M. J. Lilley Crystal structure and mechanistic investigation of the twister ribozyme Nature Chem. Biol. 10, 739-744 (2014).
David M. J. Lilley
CR-UK Nucleic Acid Structure Group