Structural dynamics of human telomeric G-quadruplex loops studied by molecular dynamics simulations

Area of Science:

• Biochemistry
• Structural Biology
• Computational Chemistry

Background:

• G-quadruplex structures are vital in biological processes.
• TTA loops are common linkers in human telomeric G-quadruplexes (hTel).
• Understanding loop dynamics is key to G-quadruplex function.

Purpose of the Study:

• Investigate the structural dynamics of TTA loops in G-quadruplexes.
• Analyze the stability and conformational behavior of TTA loop structures.
• Characterize the role of TTA loops in G-quadruplex stability.

Main Methods:

• Utilized molecular dynamics (MD) simulations.
• Analyzed hydrogen bond occupancies and base stacking interactions.
• Simulated long-time conformational dynamics of TTA loops.

Main Results:

• TA base pairs within TTA loops exhibit high stability (hydrogen bond occupancy > 0.95).
• TA base pairs enhance the stability of adjacent G-quartets.
• Edgewise and diagonal TTA loops show distinct stacking patterns and stabilities, with some exhibiting spontaneous conformational switches.
• Double chain reversal loops are conformationally unstable under current simulation conditions.

Conclusions:

• TTA loops, particularly TA base pairs and G-quartet stacking, contribute significantly to G-quadruplex stability.
• Conformational flexibility and switches in TTA loops are important dynamic features.
• Current force fields may limit the accurate simulation of certain TTA loop conformations like double chain reversals.