Aptamers selected for higher-affinity binding are not more specific for the target ligand

Area of Science:

• Biochemistry
• Molecular Biology
• RNA Aptamer Research

Background:

• In vitro selection generates RNA aptamers that bind targets like guanosine triphosphate (GTP).
• Higher affinity aptamers are assumed to possess greater binding pocket complementarity.
• Understanding the structural basis for high-affinity aptamer binding is crucial.

Purpose of the Study:

• Investigate the relationship between binding affinity and specificity in RNA aptamers targeting GTP.
• Determine if higher affinity correlates with enhanced binding specificity for GTP.

Main Methods:

• Utilized eleven previously selected RNA aptamers with varying affinities for GTP.
• Performed competition binding assays using GTP analogues to assess specificity.
• Analyzed binding patterns to infer structural solutions for GTP binding.

Main Results:

• Each of the eleven GTP aptamers exhibited unique specificity patterns, indicating distinct structural solutions.
• No direct evidence was found supporting that higher-affinity aptamers bind more specifically to GTP.
• Binding pocket complementarity may not be the sole determinant of increased affinity.

Conclusions:

• RNA aptamer affinity may be enhanced by increased tertiary structure stability through intramolecular interactions.
• Enhanced binding specificity might require direct selection rather than solely relying on affinity-driven selection.
• The structural basis for high-affinity aptamer binding is complex and not solely dependent on ligand complementarity.