How is DNA replication modified to allow the 5'-3' DNA strand to be replicated?
This process comprises three steps: (1) recognition of the origin B protein(i.e., 5'-3' helicase; also acts as the activator of primase). Thus, Dna-A (or initiator protein) ATP complex binds at 9bp inverted repeat regions (R1, R2, R3, R4) of ori C of E.coli and promotes popening of the DNA duplex in a region og three direct repeats of 13-bp sequence called 13-mers. The opening occurs from right 13-mer leftwards and requires negatively supercoiled DNA and HU or IHF initiator proteins. Dna B is transferred to exposed single stranded DNA and causes unwinding of the DNA in the presence of ATP, SSB protein and DNA gyrase.