RB69 DNA polymerase structure, kinetics, and fidelity

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• B family replicative DNA polymerases exhibit exceptionally high fidelity.
• Understanding the molecular mechanisms underlying this fidelity is crucial for DNA replication and repair research.

Purpose of the Study:

• To elucidate the structural and kinetic basis of RB69 DNA polymerase (RB69pol) high fidelity.
• To investigate the role of various interactions in nucleotide selection and primer extension.

Main Methods:

• Structural studies of RB69pol ternary complexes.
• Pre-steady-state kinetic assays.
• Development of a Förster resonance energy transfer (FRET) assay to monitor primer terminus partitioning.

Main Results:

• Interbase hydrogen bonds significantly increase catalytic efficiency (up to 5000-fold) but are not the sole determinant of base selectivity.
• Minor-groove hydrogen bonding interactions are critical for efficient primer extension and base selectivity.
• Partial charge interactions and steric clashes within the nascent base pair binding pocket (NBP) contribute to the inefficient incorporation of incorrect nucleotides.

Conclusions:

• The high fidelity of RB69pol results from a combination of specific hydrogen bonding, charge, and steric interactions.
• These factors collectively ensure accurate DNA synthesis by discriminating against mismatched nucleotides.