TLS Online TPP Program

#Id: 3030

#Unit 3. Fundamental Processes

The use of a single type of catalytic subunit, however, may be atypical. In the bacterium Bacillus subtilis, there are two different catalytic subunits.

PolC is the homolog to E. coli's DnaE, and is responsible for synthesizing the leading strand.

A related protein, DnaE8 s. is the catalytic subunit that synthesizes the lagging strand.

TLS Online TPP Program

#Id: 3031

#Unit 3. Fundamental Processes

The DNA Pol III holoenzyme has at least two catalytic cores. a processivity clamp, and a dimerization damp-loader complex.

TLS Online TPP Program

#Id: 3032

#Unit 3. Fundamental Processes

DNA polymerase III holoenzyme assembles in stages, generating an enzyme complex that synthesizes the DNA of both new strands.\

Binding to DNA changes the conformation of the site on B that binds to the clamp loader, and as a result it now has a high affinity for the core polymerase.

First the clamp loader uses hydrolysis ofATPtobindbeta subunits to a template primercomplex.

Binding to DNA changes the conformation of the site on B that binds to the clamp loader, and as a result it now has a high affinity for the core polymerase.

tau. dimer binds to the core polymerase, and provides a dimerization function thatbinds a second core polymerase (associated with another B2 

TLS Online TPP Program

#Id: 3033

#Unit 3. Fundamental Processes

The two cores have different abilities to dissociate from DNA. This corresponds to the need to synthesize 

a continuous leading strand (where polymerase remains associated  with the template) and 

a discontinuous lagging strand (where polymerase repetitively dissociates and reassociates)

TLS Online TPP Program

#Id: 3034

#Unit 3. Fundamental Processes

The core on the leading strand is processive because its clamp keeps it on the DNA.

TLS Online TPP Program

#Id: 3035

#Unit 3. Fundamental Processes

The clamp associated with the core on the lagging strand dissociates at the end of each Okazaki fragment and reassembles for the next fragment.