Translocation of an RNA duplex on a ribozyme

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• The Tetrahymena ribozyme catalyzes RNA cleavage, a process dependent on precise recognition of the reaction-site helix by its catalytic core.
• This recognition is not fixed, as the helix can bind in multiple registers, leading to cleavage at distinct positions.

Purpose of the Study:

• To identify the molecular interactions responsible for the Tetrahymena ribozyme's ability to bind the reaction-site helix in alternative registers.
• To elucidate the mechanism underlying the translocation of the reaction site within the ribozyme's binding pocket.

Main Methods:

• Investigated 2 -hydroxyl interactions on both strands of the reaction-site helix.
• Analyzed the structural basis for alternative binding alignments within the ribozyme's catalytic apparatus.

Main Results:

• Identified specific, commensurate sets of 2 -hydroxyl interactions that mediate the helix's translocation into different binding registers.
• Demonstrated that the ribozyme possesses a rigid substrate-binding pocket capable of accommodating the helix in varied alignments.
• Provided evidence for a similar recognition mechanism in intron circularization and ribozyme polymerase activity.

Conclusions:

• The binding flexibility of the Tetrahymena ribozyme's reaction site arises from specific 2 -hydroxyl interactions enabling register shifting.
• This mechanism highlights structural heterogeneity in RNA tertiary folding, exemplified by helix packing during translocation.
• The findings offer insights into RNA-protein interactions and catalytic mechanisms in other ribozyme-mediated processes.