Prokaryotic DNA polymerase I: evolution, structure, and "base flipping" mechanism for nucleotide selection

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• DNA polymerase I (Pol I) enzymes are foundational models for DNA replication studies.
• Recent genomic, mutagenesis, and structural data offer new insights into Pol I function and evolution.

Purpose of the Study:

• To review the structure-function relationships of Pol I enzymes.
• To highlight interactions critical for high-fidelity DNA synthesis.
• To present a base-flipping mechanism in DNA synthesis.

Main Methods:

• X-ray crystallography of Pol I enzymes with DNA and dNTP.
• Rapid-quench stop-flow studies of nucleotide incorporation.
• Generation and biochemical analysis of mutant Pol I enzymes.
• Genomic sequencing of over 50 polA genes.

Main Results:

• Detailed description of productive replication complexes.
• Identification of rate-limiting steps and conformational changes in catalysis.
• Characterization of mutant enzymes with altered biochemical properties.
• Availability of extensive genomic information for Pol I.

Conclusions:

• Structure-function relationships of Pol I are increasingly understood.
• Specific interactions within Pol I are responsible for high-fidelity DNA synthesis.
• A base-flipping mechanism enhances nucleotide substrate interaction during DNA synthesis.