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A Model for DNA Replication Initiation

The solution structure of the DnaA N terminus.

In Escherichia coli, DNA replication is initiated by DnaA, a protein that binds to a region known as the DnaA box on the chromosome's replication origin (oriC). Once bound to oriC, a homomultimer of DnaA unwinds a duplex of AT-rich 13-mer repeats within oriC, forming an open complex. This leads to the loading of DnaB helicase onto the single-stranded DNA, unwinding of the DNA, and subsequent DNA synthesis.

In this Paper of the Week, Yoshito Abe and colleagues used NMR to solve the structure of the E. coli DnaA N terminus, a region that is essential for DnaA oligomerization and DnaB binding. They showed that Trp-6 may participate in subunit dimerization and that Glu-21 is a crucial residue for the initiation process in as much as it is required for helicase loading. From these results, Abe et al. propose a novel model of DnaA homo-oligomer formation and DnaB helicase loading.

FOOTNOTES

See referenced article, J. Biol. Chem. 2007, 282, 17816-17827

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