Question

How does DnaA prevent reinitiating at the origin until the next cycle?

DnaA must be bound to ____ in order for the protein to bind the DnaA boxes at the origin

After binding oriC, DnaA has ____ activity, which prevents further binding

Answer 1

DnaA prevents reinitiation of replication at oriC by binding to ATP, initiating replication, and then undergoing ATPase activity which hydrolyzes ATP to ADP, rendering DnaA unable to bind oriC until the next cycle.

Step-by-step explanation:

The student's question is related to the process by which DnaA prevents premature reinitiating of DNA replication at the origin, ensuring that replication occurs only once per cell cycle in prokaryotes like E. coli. DnaA must be bound to ATP in order to bind the DnaA boxes at the origin of replication, known as oriC. After binding oriC, DnaA exhibits ATPase activity, which hydrolyzes its bound ATP to ADP, reducing its affinity for the origin and thus preventing additional reinitiating events until the next cycle. This mechanism is crucial for maintaining the fidelity of DNA replication, as unregulated reinitiation could lead to DNA over-replication and genomic instability. The ATP-bound form of DnaA is active in initiating replication, while the ADP-bound form is inactive. This cycle of ATP binding and hydrolysis facilitates the temporal regulation of DNA replication initiation.