The charging of a tRNA with its cognate amino acid is a remarkably accurate process.

Experimental measurements indicate, for example, that at equal concentrations of isoleucine and valine, IleRS transfers ∼40,000 isoleucines to tRNAIle for every valine it so transfers.

TLS Online TPP Program

#Id: 5058

#Unit 3. Fundamental Processes

Each DnaB–DnaC complex consists of six DnaC monomers bound to a hexamer of DnaB.

Note that the DnaB helicase cannot open double-stranded DNA; it can only unwind DNA that has already been opened, in this case by DnaA.

DnaB binding to single-stranded DNA is the signal to hydrolyze ATP and for release of DnaC.

TLS Online TPP Program

#Id: 5059

#Unit 3. Fundamental Processes

Two-state assembly model of bacterial replication initiation

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.