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 hydrolysis^[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 AT-rich region to unwind. The denatured AT-rich region allows for the recruitment of DnaB (helicase) complexes 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) stabilise the single DNA strands in order to maintain the replication bubble. 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

• MeSH DnaA+protein,+Bacteria

References

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