Use of intrinsic binding energy for catalysis by an RNA enzyme

Klemens J. Hertel, Alessio Peracchi, Olke C. Uhlenbeck, Daniel Herschlag*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

51 Scopus citations

Abstract

The contribution of several individual ribozyme-substrate base pairs to binding and catalysis has been investigated using hammerhead ribozyme substrates that were truncated at their 3' or 5' ends. The base pairs at positions 1.1-2.1 and 15.2-16.2, which flank the conserved core, each contribute 104-fold in the chemical step, without affecting substrate binding. In contrast, base pairs distal to the core contribute to substrate binding but have no effect on the chemical step. These results suggest a 'fraying model' in which each ribozyme-substrate helix can exist in either an unpaired ('open') state or a helical ('closed') state, with the closed state required for catalysis. The base pairs directly adjacent to the conserved core contribute to catalysis by allowing the closed state to form. Once the number of base pairs is sufficient to ensure that the closed helical state predominates, additional residues provide stabilization of the helix, and therefore increase binding, but have no further effect on the chemical step. Remarkably, the > 5 kcal/mol free energy contribution to catalysis from each of the internal base pairs is considerably greater than the free energy expected for formation of a base pair. It is suggested that this unusually large energetic contribution arises because free energy that is typically lost in constraining residues within a base pair is expressed in the transition state, where it is used for positioning. This extends the concept of 'intrinsic binding energy' from protein to RNA enzymes, suggesting that intrinsic binding energy is a fundamental feature of biological catalysis.

Original languageEnglish (US)
Pages (from-to)8497-8502
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume94
Issue number16
DOIs
StatePublished - Aug 5 1997

ASJC Scopus subject areas

  • General

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