trp Repressor interactions with the trparoH and trpR operators. Comparison of repressor binding in vitro and repression in vivo

Lisa S. Klig, Jannette Carey, Charles Yanofsky

Research output: Contribution to journalArticle

51 Scopus citations

Abstract

Interaction of the Escherichia coli trp repressor with the promoter-operator regions of the trp, aroH and trpR operons was studied in vivo and in vitro. The three operators have similar, but non-identical, sequences; each operator is located in a different segment of its respective promoter. In vivo repression of the three operons was measured using single-copy gene fusions to lacZ. The extent of repression varied from 300-fold for the trp operon, to sixfold for the aroH operon and threefold for the trpR operon. To determine whether differential binding of repressor to the three operators was responsible for the differences in repression observed in vivo, three in vitro binding assays were employed. Restriction-site protection, gel retardation and DNase footprinting analyses revealed that repressor binds to the three operators with almost equal affinity. It was also shown in an in vivo competition assay that repressor binds approximately equally well to each of the three operators. It is proposed that the differential regulation observed in vivo may be due to the different relative locations of the three operators within their respective promoters.

Original languageEnglish (US)
Pages (from-to)769-777
Number of pages9
JournalJournal of Molecular Biology
Volume202
Issue number4
DOIs
StatePublished - Aug 20 1988
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Structural Biology
  • Molecular Biology

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