The SH3 domains in GRB2 selectively bind to 

proline-rich sequences in Sos

TLS Online TPP Program

#Id: 5913

#Unit 3. Fundamental Processes

DnaG primase associates transiently with the replication complex, and typically synthesizes a 10-base primer. Primers start with the sequence pppAG positioned opposite the sequence 3’–GTC-5’ in the template.

TLS Online TPP Program

#Id: 5914

#Unit 3. Fundamental Processes

There are two types of priming reaction in E. coli: The oriC system, named for the bacterial origin, basically involves the association of the DnaG primase with the protein

complex at the replication fork.

TLS Online TPP Program

#Id: 5915

#Unit 3. Fundamental Processes

Replicons are referred to as being of the PhiX or oriC type.

TLS Online TPP Program

#Id: 5916

#Unit 3. Fundamental Processes

TLS Online TPP Program

#Id: 5917

#Unit 3. Fundamental Processes

The holoenzyme is a complex of 900 kD that contains 10 different proteins organized into four types of subcomplex

1. Atleast two copies of the catalytic core.

2. two copies of the dimerizing subunit, t, which link the two catalytic cores together.

3. There are two copies of the clamp

4. The g complex is a group of seven proteins, encoded by five genes, that comprise the clamp loader

TLS Online TPP Program

#Id: 5918

#Unit 3. Fundamental Processes

The holoenzyme assembles on replication fork DNA in three stages:

1. First the clamp loader uses hydrolysis of ATP to bind b subunits to a template primer complex.

2. 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

3. A t dimer binds to the core polymerase, and provides a dimerization function that binds a second core polymerase