Lactose promoter mutation Pr115 activates an overlapping promoter within the lactose control region

Martha L. Peterson, William S. Reznikoff

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22 Scopus citations


The Escherichia coli lac promoter mutation Pr115, an A · T to T · A transversion at +1 (the transcription initiation site of the lac wild-type and lac UV5 promoters), creates a new "-10 region"-like sequence starting at +1. We show that this mutation activates a new RNA polymerase binding site (P115) that overlaps with, and is shifted 12 base-pairs downstream from, the wild-type RNA polymerase binding site (P1). Nuclease S1 mapping studies and RNA polymerase protection experiments in vitro indicate that, in the absence of CAP-cAMP, this new site is used preferentially over the P1 site. In vivo, β-galactosidase assays of the Pr115 mutation in combination with mutations of the P1 "-35 region" demonstrate that the P1 -35 region sequences are not involved in the interaction between RNA polymerase and P115 in the absence of CAP-cAMP; therefore P115 is an independent binding site. The presence of CAP-cAMP in vivo stimulates polymerase binding and initiation at P1, which serves to block polymerase from binding at P115.

Original languageEnglish
Pages (from-to)525-533
Number of pages9
JournalJournal of Molecular Biology
Issue number3
StatePublished - Oct 5 1985

Bibliographical note

Funding Information:
The authors thank Yu Xian-Ming. Paul Lambert and Marvin Wickens for critical reading of this manuscrupt. This work was supported by the National Institute of Health grant GM19670 and a 3M Foundation grant to W.S.R. and M.L.P. was supported in part by the National Institute of Health training grant GM07215-07.

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology


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