Balancing Non-Equilibrium Driving with Nucleotide Selectivity at Kinetic Checkpoints in Polymerase Fidelity Control.

Area of Science:

• Biochemistry and Molecular Biology
• Enzyme Kinetics
• Genetics

Background:

• High-fidelity gene transcription and replication depend on accurate nucleotide discrimination by polymerases.
• Maintaining non-equilibrium conditions is essential for achieving low error rates during polymerization.
• Polymerase elongation involves multiple kinetic steps, each with distinct transition rates.

Purpose of the Study:

• To investigate how accelerations at different kinetic steps affect overall polymerase elongation characteristics.
• To understand the balance between nucleotide selectivity and non-equilibrium driving force for low error rates.
• To explore the role of individual transition rates in polymerase error control.

Main Methods:

• Utilized three-state and five-state models of nucleotide addition during polymerase elongation.
• Analyzed changes in non-equilibrium steady-state characteristics by varying stepwise forward or backward kinetics.
• Applied multi-step elongation schemes and parameters from T7 RNA polymerase transcription elongation.

Main Results:

• Accelerations at different kinetic steps have significantly different impacts on elongation.
• Optimal error control requires a balance between nucleotide selectivity and non-equilibrium driving force at selection checkpoints.
• Individual transitions acting as selection checkpoints should proceed at moderate rates for optimal error control.

Conclusions:

• The balance between kinetic step rates is critical for achieving high fidelity in polymerase activity.
• Moderate rates at selection checkpoints are necessary to maintain non-equilibrium drives and ensure nucleotide selectivity.
• Rate-limiting conformational transitions are likely important for reducing errors during gene transcription and replication.