One metal ion reduces the affinity of the 3’-OH for its hydrogen. This generates a 3’O- that is primed for the nucleophilic attack of the a-phosphate of the incoming dNTP. 

TLS Online TPP Program

#Id: 5060

#Unit 3. Fundamental Processes

Input of energy in the form of ATP is required at several stages for the prepriming reaction, and it is required for unwinding DNA.

The helicase action of DnaB depends on ATP hydrolysis, and the swivel action of gyrase requires ATP hydrolysis.

ATP also is needed for the action of primase and to load the b subunit of Pol III in order to initiate DNA synthesis.

TLS Online TPP Program

#Id: 5061

#Unit 3. Fundamental Processes

SeqA binds to hemimethylated DNA and is required for 13 min delaying rereplication.

TLS Online TPP Program

#Id: 5062

#Unit 3. Fundamental Processes

As the origins are hemimethylated they bind to the cell membrane and become unavailable to methylases.

TLS Online TPP Program

#Id: 5063

#Unit 3. Fundamental Processes

Replication in bacteria and in eukaryotes is licensed and permitted to occur only once per cell cycle. Each replicon is allowed to fire only once.

TLS Online TPP Program

#Id: 5064

#Unit 3. Fundamental Processes

13 minutes delaying, sequesters Oric regions in a form in which they are inaccessible to the Dam methylase and this is done by SeqA protein.

TLS Online TPP Program

#Id: 5065

#Unit 3. Fundamental Processes

SeqA mutants reduce the delay in remethylation at both oriC and dnaA. As a result, they initiate DNA replication too soon, thereby accumulating an excessive number of origins.