Phosphorylation leads to a conformational change in the activation loop that unblocks kinase active site by reducing the Kd for ATP or the substrate to be phosphorylated.

TLS Online TPP Program

#Id: 5050

#Unit 3. Fundamental Processes

DnaA is an ATP-binding protein.

The first stage in initiation is binding of the DnaA-ATP protein complex to the fully methylated oriC sequence.

This takes place in association with the inner membrane. DnaA is in the active form only when bound to ATP.

DnaA has intrinsic ATPase activity that hydrolyzes ATP to ADP and thus inactivates itself when the initiation stage ends.

TLS Online TPP Program

#Id: 5051

#Unit 3. Fundamental Processes

DnaA ATPase activity is stimulated by membrane phospholipids and single-stranded DNA.

TLS Online TPP Program

#Id: 5052

#Unit 3. Fundamental Processes

DnaA-ATP in an extended multimeric state promoted by the accessory protein DiaA, which stimulates cooperative binding of DnaA.

DnaA-ATP binds cooperatively to form a helical central core around which oriC DNA is wrapped.

TLS Online TPP Program

#Id: 5053

#Unit 3. Fundamental Processes

DnaA has a weak ATPase intrinsic activity which is enhanced by a factor termed Hda.

In a conceptually elegant feedback loop, Hda is recruited to a replication origin via the b subunit of the DNA polymerase. it acts to switch off DnaA

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#Id: 5054

#Unit 3. Fundamental Processes

Phospholipids promote the exchange of ATP with ADP bound to DnaA

TLS Online TPP Program

#Id: 5055

#Unit 3. Fundamental Processes

DnaA then acts at three A-T–rich 13-bp tandem repeats located on the left side of oriC.