lac repressor forms loops with linear DNA carrying two suitably spaced lac operators.

H. Krämer, M. Niemöller, M. Amouyal, B. Revet, B. von Wilcken-Bergmann, B. Müller-Hill

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255 Scopus citations

Abstract

Tetrameric lac repressor may bind to two lac operators on one DNA fragment and induce the intervening DNA to form a loop. Electron microscopy, non-denaturing polyacrylamide gel electrophoresis, and DNase I protection experiments were used to demonstrate such DNA loops, where the distance between the centres of symmetry of the two lac operators varies between 63 and 535 bp. Formation of a DNA loop is favoured by correct phasing of the two lac operators and a low concentration of both components of the reaction. When a large excess of lac repressor over DNA is used, a 'tandem' structure is observed, in which both lac operators are occupied independently by two repressor tetramers. When the concentrations of both lac repressor and lac operator are high, a 'sandwich' structure is observed, in which two DNA molecules are connected by two lac repressor tetramers in trans.

Original languageEnglish (US)
Pages (from-to)1481-1491
Number of pages11
JournalEMBO Journal
Volume6
Issue number5
StatePublished - May 1 1987

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)

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    Krämer, H., Niemöller, M., Amouyal, M., Revet, B., von Wilcken-Bergmann, B., & Müller-Hill, B. (1987). lac repressor forms loops with linear DNA carrying two suitably spaced lac operators. EMBO Journal, 6(5), 1481-1491.