DNA Replication Proteins

helicase

unzips parental double helix at replication forks — breaks the weak hydrogen bonds connecting the base pairs

primase

synthesizes an RNA primer at 5’ end of leading strand & at 5’ end of each Okazaki fragment of lagging strand

single-strand binding proteins (SSB)

binds to and stabilizes ssDNA until it is used as a template

• coats the ssDNA that is exposed to ensure the 2 strands do not zip back together until copied

topoisomerase II

relieves overwinding strain ahead of replication forks by breaking, swiveling, and rejoining DNA strands

• prevents DNA from being extremely tangled

DNA polymerase I

removes RNA nucleotides of primer from 5’ end and replaces them w/ nucleotides added to 3’ end of adjacent fragment

• removes short RNA primers used to initiate DNA synthesis and fills the resulting gaps w/ DNA

DNA polymerase III

using parental DNA as a template, synthesizes new DNA strand by adding nucleotides to an RNA primer/a pre-existing DNA strand

• synthesizes the vast majority of new DNA

DNA ligase

joins okazaki fragments of lagging strand; on leading strand, joins 3’ end of DNA that replaces primers to rest of leading strand DNA

• joins DNA all together