Volume 90 Issue 16 | p. 41 | Concentrates
Issue Date: April 16, 2012

Precatalytic Intron Structure Solved

Pre- and postcatalytic structures of a self-splicing RNA molecule (the group II intron from a bacterium) are similar
Department: Science & Technology
News Channels: Analytical SCENE, Biological SCENE
Keywords: RNA, intron, splicing
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This close-up depiction of the precatalytic group II intron 5ʹ splice site shows the 5ʹ end of the intron (green), the catalytic domain (red), and the 5ʹ exon (dark blue).
Credit: Courtesy of Navtej Toor
Close up of group II intron 5' splice site; shown are the 5' end of introm (green), catalytic domain (red), and 5' exon (blue).
 
This close-up depiction of the precatalytic group II intron 5ʹ splice site shows the 5ʹ end of the intron (green), the catalytic domain (red), and the 5ʹ exon (dark blue).
Credit: Courtesy of Navtej Toor

The first crystal structure of the precatalytic state of a group II intron has been solved (Nat. Struct. Mol. Biol., DOI: 10.1038/nsmb.2270). Previous structures of these self-splicing RNA molecules, which are thought to be evolutionary predecessors of the spliceosome, have captured them either during or after the splicing process, but never before splicing starts. Navtej Toor of the University of California, San Diego, and coworkers obtained a 3.65-Å crystal structure of the group II intron from the ocean sediment bacterium Oceanobacillus iheyensis in its precatalytic state. To trap this state, the researchers deactivated the catalytic site with a single-point mutation. The structure shows that the 5ʹ splice site has a kinked structure before catalysis, which had been predicted. The researchers propose that this structural distortion of splice sites is a general mechanism inherent to all RNA-splicing reactions. They also modeled the probable position of the 3ʹ splice site and used this information to propose a mechanism for the entire splicing pathway. Their model suggests that the active site can accommodate both splicing steps with relatively small conformational alteration.

 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society

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