The transition from the closed to the open complex involves structural changes in the enzyme and the opening of the DNA double helix to reveal the template and nontemplate strands. This “melting” occurs between positions –11 and +2, with respect to the transcription start site.

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#Unit 3. Fundamental Processes

The lac promoter along with the bulk of other E. coli promoters, is recognized by RNA polymerase bearing the σ70 subunit.

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#Unit 3. Fundamental Processes

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#Unit 3. Fundamental Processes

The subunits of RNA Polymerases

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#Unit 3. Fundamental Processes

Template and transcript within the RNA polymerase elongating complex

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#Unit 3. Fundamental Processes

Core enzyme without the s subunit could not transcribe viral DNA, yet had no problems with highly nicked calf thymus DNA

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#Unit 3. Fundamental Processes

With s subunit, the holoenzyme worked equally well on both types of DNA