Abstract
Divalent metal ions are required for splicing of group I introns, but their role in maintaining the structure of the active site is still under investigation. Ribonuclease and hydroxyl radical footprinting of a small group I intron from Azoarcus pre-tRNAIle showed that tertiary interactions between helical domains are stable in a variety of cations. Only Mg2+, however, induced a conformational change in the intron core that correlates with self-splicing activity. Three metal ion binding sites in the catalytic core were identified by Tb(III)-dependent cleavage. Two of these are near bound substrates in a three-dimensional model of the ribozyme. A third metal ion site is near an A minor motif in P3. In the pre-tRNA, Tb3+ cleavage was redirected to the 5′ and 3′ splice sites, consistent with metal-dependent activation of splice site phosphodiesters. The results show that many counterions induce global folding, but organization of the group I active site is specifically linked to Mg2+ binding at a few sites.
Original language | English (US) |
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Pages (from-to) | 229-238 |
Number of pages | 10 |
Journal | Journal of molecular biology |
Volume | 329 |
Issue number | 2 |
DOIs | |
State | Published - May 30 2003 |
Externally published | Yes |
Keywords
- Equilibrium phase diagram
- Group I ribozyme
- Metal ions
- RNA folding
- RNA stability
ASJC Scopus subject areas
- Structural Biology
- Molecular Biology