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Small angle X-ray scattering reveals a compact intermediate in RNA folding
R Russell1, I S Millett, S Doniach
1Department of Biochemistry, Stanford University, Stanford, California 94305, USA.
Nature Structural Biology
|May 10, 2000
Summary
Small angle X-ray scattering reveals that Tetrahymena ribozyme folding involves an early electrostatic collapse. This rapid compaction precedes slower rearrangements, forming a compact intermediate before reaching the native state.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Ribozymes are RNA molecules with catalytic activity.
- Understanding RNA folding is crucial for comprehending biological function.
- The Tetrahymena ribozyme serves as a model system for studying RNA folding dynamics.
Purpose of the Study:
- To monitor the changes in size and shape of the Tetrahymena ribozyme during folding.
- To investigate the kinetics of Tetrahymena ribozyme folding.
- To elucidate the intermediate states involved in Tetrahymena ribozyme folding.
Main Methods:
- Small-angle X-ray scattering (SAXS) was employed to track structural changes.
- Time-resolved SAXS measurements were performed to capture folding kinetics.
- The study monitored the ribozyme in the presence of Mg2+.
Main Results:
- The native Tetrahymena ribozyme is significantly more compact and globular than its unfolded state.
- Most of the compaction occurs much faster (at least 20-fold) than the overall folding process.
- A compact intermediate or family of intermediates is formed early in the folding pathway.
Conclusions:
- RNA folding involves distinct kinetic phases, including rapid compaction and slower rearrangements.
- An initial 'electrostatic collapse' drives early RNA compaction.
- Subsequent slower steps involve the rearrangement of mispositioned elements to achieve the native ribozyme structure.