Bacterial DNA Replication Proteins

Helicase

Leading & Lagging Strands: Unwinds parental double helix at replication forks.

Single-strand binding protein

Leading & Lagging Strands: Binds to and stabilizes single-stranded DNA until it can be used as a template.

Topoisomerase

Leading & Lagging Strands: Corrects “overwinding” ahead of replication forks by breaking, swiveing, and rejoining DNA strands.

Primase

Leading Strand: Synthesizes a single RNA primer at the 5’ end of the leading strand.

Lagging Strand: Synthesizes an RNA primer at the 5’ end of each Okazaki fragment.

DNA pol III

Leading Strand: Continuously synthesizes the leading strand, adding on to the primer.

Lagging Strand: Elongates each Okazaki fragment, adding on to its primer. 

DNA pol I

Leading Strand: Removes primer from the 5’ end of leading strand and replaces it with DNA, adding on to the adjacent 3’ end.

Lagging Strand: Removes the primer from the 5’ end of each fragment and replaces it with DNA, adding on to the 3’ end of the adjacent fragment.

DNA Ligase

Leading Strand: Joins the 3’ end of the DNA that replaces the primer to the rest of the leading strand.

Lagging Strand: Joins the Okazaki fragments.