The activity of helicase causes the topological stress to the unwinded strand forming supercoiled DNA.dnaB migrates along the single stranded DNA in 5’-3’ direction causing unwinding of the DNA. The binding of helicase is key step in replication initiation.The hydrolysis of bound ATP release dnaC leaving the dnaB bound to the DNA strand. The dnaB-dnaC interaction causes dnaB ring to open which binds with each of the DNA strand. This binding is facilitated by another molecule called dnaC. Two copies of dnaB proteins (helicase) binds to 13 mer repeats.The dna A protein and ATP trigger the opening of 13 mer repeats froming open complex. About 20 molecules of Dna A proteins binds with 9 mer repeats along with ATP which causes DNA to wraps around dnaA protein forming initial complex.Two types of conserved sequences are found at OriC, three repeats of 13 bp (GATRCTNTTNTTTT) and four/five repeats of 9 bp (TTATCCACA) called 13 mer and 9 mer respectively. In E coli, replication origin is called OriC which consists of 245 base pair and contains DNA sequences that are highly conserved among bacterial replication origin. Termination DNA replication in prokaryotesĭNA replication begins from origin. It proceed from a specific point called originģ.The process is called replication in sense that each strand of ds DNA serve as template for reproduction of complementary strand. DNA replication is fundamental process occurring in all living organism to copy their DNA.
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