Bacterial DNA Polymerase I

Abstract

Abstract Bacterial deoxyribonucleic acid (DNA) polymerase I is a family of enzymes involved in bacterial DNA synthesis and lesion repair. These enzymes have a multidomain structure, consisting of a single polypeptide chain that encompasses a distinct polymerase domain, a proofreading 3′–5′ exonuclease and/or a 5′–3′ exonuclease activity. Members of the polymerase I family have been investigated extensively, both because of their vital role in replicating and maintaining bacterial chromosomes, and because of their importance as tools in molecular biology, in particular for the polymerase chain reaction (PCR) and DNA sequencing. Studies on the Escherichia coli DNA polymerase I in particular have yielded significant insights into the mechanism of DNA polymerisation which is shared by almost all other nucleotide polymerases. Key Concepts: Bacterial DNA polymerase I enzymes are multidomain proteins with separate polymerisation, proofreading and 5′–3′ exonuclease functions. They perform a vital function in bacteria by carrying out DNA repair and some aspects of chromosomal replication. Polymerases incorporate one nucleotide at a time to the 3′ end of the primer DNA strand in a template‐directed manner. Members of the DNA polymerase I family are able to replicate DNA with far greater accuracy than base pairing alone can account for. The polymerisation reaction is a multistep process during which the enzyme switches between substrate binding and nucleotide incorporation conformations. The 5′–3′ exonuclease allows the polymerase to degrade RNA primers and to assist with DNA repair. Thermostable family I DNA polymerases are used extensively in polymerase chain reaction to amplify DNA and for DNA sequencing.