TLS Online TPP Program

#Id: 760

#Unit 3. Fundamental Processes

Promoter search->closed promoter complex -> open promoter complex

TLS Online TPP Program

#Id: 761

#Unit 3. Fundamental Processes

Sigma factor ensures that bacterial RNA polymerase initiates transcription from specific sites, also reduces binding to nonspecific sequences.

TLS Online TPP Program

#Id: 762

#Unit 3. Fundamental Processes

TLS Online TPP Program

#Id: 763

#Unit 3. Fundamental Processes

The transition from the closed to the open complex involves “melting” between positions –11 and +2, with respect to the transcription start site.

TLS Online TPP Program

#Id: 764

#Unit 3. Fundamental Processes

Transition from CPC to OPC often called isomerization, does not require energy derived from ATP hydrolysis and is instead the result of a spontaneous conformational change in the DNA– enzyme complex to a more energetically favorable form.

TLS Online TPP Program

#Id: 765

#Unit 3. Fundamental Processes

The closed complex is converted into an open complex of 1.3 turns of the double helix in a series of steps by first “melting” a short region of DNA. 

This Isomerization is essentially irreversible and, once complete, typically guarantees that transcription will subsequently initiate.