Events at initiation of

transcription

Abortive initiation assay

Let R = RNA polymerase, P = promoter (closed), and Po= promoter (open)

R + P RP RPoATP + UTP*

ApUp*U

kf

kr

KB

Abortive transcripts

[ApUp*U]

time

lag

Measure kf and KB from lag time vs. 1/[R]

Lag time

Lag time in abortive initiation assay is inversely proportional to [R].

Lag time = KB kf

1

kf

1x +1

[R]

1

[R]Y-intercept = kf

1

Slope = KB kf

1

Effect of wild-type and pc mutant λ repressors on activity of PR & PRM

Effect of Operator Mutations on Transcriptional Control of PR&PRM

OR1-OR2+OR3- OR1+OR2-OR3+

Effect of λ-pc mutations on KB and k2

Architecture of λOR

Mutations in the Activating Region ofλ Repressor

Glu

Glu

Glu

Mutations in the δ subunit of RNA polymerase that interfere w/λ repressor-mediated activation of PRM transcription

Effect of mutations in the δ subunit of RNA polymerase on activator-dependent and independent transcription of the lac

promoter

A model for interaction of the δ subunit of RNA polymerase with λ repressor

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