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#strong promoters

2 public questions tagged with this topic.

Lac Operon

Strong promoters usually require

Strong promoters possess near-perfect -35 TTGACA and -10 TATAAT hexamers separated by optimal 17 base pair spacer including AT-rich UP element interacting with alpha C-terminal domain, producing exceptionally high intrinsic affinity for sigma70 holoenzyme and spontaneous open complex formation. Uncontrolled activity would wastefully consume nucleotides, ribosomes, and energy producing unnecessary transcripts. Evolution pairs potent cores with repressor proteins whose operators overlap start site, creating steric block until specific signal inactivates repressor. Net effect is high regulatory r

Ref: Alberts Molecular Biology of the Cell – strong promoters require repressors to prevent wasteful constitutive transcription.

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Transcription in Prokaryotes

Strong promoters are those which

Transcription initiation frequency governed by affinity of RNA polymerase holoenzyme for promoter DNA, which depends on similarity to consensus hexamers. Promoters whose -10 and -35 elements exactly match consensus TTGACA and TATAAT with optimal seventeen base pair spacing and AT-rich UP element bind sigma with high affinity forming stable closed complex rapidly isomerizing to open complex. Consequently such promoters described as strong produce abundant transcripts per unit time. Those diverging at multiple positions exhibit low intrinsic affinity, termed weak promoters requiring activators l

Ref: Lodish Molecular Cell Biology Chapter 8: Strong promoters close to consensus sequence; Alberts Chapter 7 Promoter strength affinity model

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