Involvement of a specific metal ion in the transition of the hammerhead ribozyme to its catalytic conformation

Alessio Peracchi, Leonid Beigelman, Edmund C. Scott, Olke C. Uhlenbeck, Daniel Herschlag*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

120 Scopus citations

Abstract

Previous crystallographic and biochemical studies of the hammerhead ribozyme suggest that a metal ion is ligated by the pro-R(p) oxygen of phosphate 9 and by N7 of G10.1 and has a functional role in the cleavage reaction. We have tested this model by examining the cleavage properties of a hammerhead containing a unique phosphorothioate at position 9. The R(p)-, but not S(p)-, phosphorothioate reduces the cleavage rate by 103-fold, and the rate can be fully restored by addition of low concentrations of Cd2+, a thiophilic metal ion. These results strongly suggest that this bound metal ion is critical for catalysis, despite its location ~20 Å from the cleavage site in the crystal structure. Analysis of the concentration dependence suggests that Cd2+ binds with a K(d) of 25 μM in the ground state and a K(d) of 2.5 nM in the transition state. The much stronger transition state binding suggests that the P9 metal ion adopts at least one additional ligand in the transition state and that this metal ion may participate in a large scale conformational change that precedes hammerhead cleavage.

Original languageEnglish (US)
Pages (from-to)26822-26826
Number of pages5
JournalJournal of Biological Chemistry
Volume272
Issue number43
DOIs
StatePublished - 1997

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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