Visualizing group II intron dynamics between the first and second steps of splicing.

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• Group II introns are self-splicing ribozymes and retrotransposable elements.
• They are evolutionarily and chemically related to the eukaryotic spliceosome.
• Group II introns have potential applications as gene-editing tools.

Purpose of the Study:

• To resolve the spatiotemporal location and function of conformational changes during group II intron splicing.
• To elucidate the mechanism connecting the first and second catalytic steps.

Main Methods:

• Enzymatic assays
• X-ray crystallography
• Molecular simulations

Main Results:

• The first residue of the catalytic triad is protonated upon 5'-splice-site scission.
• This protonation triggers a reversible active site rearrangement (toggling).
• Protonation and active site dynamics facilitate the progression to the second splicing step.

Conclusions:

• The first step of splicing induces conformational changes that promote the second step.
• Group II intron splicing mechanism shares similarities with the spliceosome.
• These findings reinforce the shared enzymatic strategy between these molecular machines.