In Vitro Interaction of the Escherichia coli Cyclic AMP Receptor Protein with the Lactose Repressor

Michael G. Fried, Margaret A. Daugherty

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Sedimentation equilibrium studies show that the Escherichia coli cyclic AMP receptor protein (CAP) and lactose repressor associate to form a 2:1 complex in vitro. This is, to our knowledge, the first demonstration of a direct interaction of these proteins in the absence of DNA. No 1:1 complex was detected over a wide range of CAP concentrations, suggesting that binding is highly cooperative. Complex formation is stimulated by cAMP, with a net uptake of 1 equivalent of cAMP per molecule of CAP bound. Substitution of the dimeric lacI-18 mutant repressor for tetrameric wild-type repressor completely eliminates detectable binding. We therefore propose that CAP binds the cleft between dimeric units in the repressor tetramer. CAP-lac repressor interactions may play important roles in regulatory events that take place at overlapping CAP and repressor binding sites in the lactose promoter.

Original languageEnglish
Pages (from-to)11226-11229
Number of pages4
JournalJournal of Biological Chemistry
Volume276
Issue number14
DOIs
StatePublished - Apr 6 2001

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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