G-Quadruplex Recognition by DARPIns through Epitope/Paratope Analogy

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Guanine Quadruplexes (G4) are non-canonical DNA structures implicated in various biological processes.
• Engineered protein binders, such as DARPins (Designed Ankyrin Repeat Proteins), offer potential for specific G4 recognition.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying the specific recognition of Guanine Quadruplexes (G4) by DARPin peptides.
• To provide insights for designing novel G4-specific sensors.

Main Methods:

• All-atom molecular dynamic simulations were employed to study DARPin/G4 interactions.
• Simulations focused on complexes formed with human-telomeric (h-telo), Bcl-2, and c-Myc G4 structures.

Main Results:

• G4 recognition by DARPins is driven by the complementarity between the 3D structures of the DARPin's α-helix/loops domain and the G4 backbone.
• Sequence similarity alone does not determine DARPin-G4 binding affinity.
• DARPins feature a charged hollow region that accommodates G4 structures, with shape complementarity dictating interaction stability.

Conclusions:

• The specific binding of DARPins to G4 structures is governed by precise structural and electrostatic complementarity.
• These findings pave the way for the rational design of highly specific G4-targeting molecules and sensors.