DnaA

DnaA is a replication initiation factor which promotes the unwinding or denaturation of DNA at oriC (around 240bp in "Escherichia coli"), during DNA replication in prokaryotes.

The formation of the oriC/DnaA complex and DNA unwinding requires ATP hydrolysisref|1.

The oriC site in "E. coli" has three AT rich 13 base pair regions (DUE's elements) followed by four 9 bp regions. Around 10 dnaA molecules bind to the 9 bp regions, which wrap around the proteins causing the DNA at the 13 bp region to unwind. The denatured 13 base pair region allows for the recruitment of DnaB (helicase) complexs with DnaC (helicase loader). DnaC helps the helicase to bind to and to properly accommodate the ssDNA at the 13 bp region, this is accomplished by ATP hydrolysis after which DnaC is released. Single-strand binding protein's (SSBs) help to prevent the double helix from reforming at the replication bubble. The DnaB is a 5'->3' helicase, so it travels on the lagging strand. It associates with DnaG (a primase) to form the only primer for the leading strand and to add RNA primers on the lagging strand. The interaction between DnaG and DnaB is necessary to control the longitude of Okazaki fragments on the lagging strand. DNA polymerase III is then able to start DNA replication.

External links

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References

*Voet, Donald; Voet, Judith; Pratt, Charlotte (2001). "Fundamentals of Biochemistry". Wiley.