Location of close contacts between Escherichia coli RNA polymerase and guanine residues at promoters either with or without consensus -35 region sequences

Biochem J. 1993 Feb 1;289 ( Pt 3)(Pt 3):771-5. doi: 10.1042/bj2890771.


Methylation-interference assays have been used to identify guanine residues that make important contacts with RNA polymerase during open-complex formation at two related Escherichia coli promoters. Methylation of lower-strand G-31 at a gal consensus promoter completely prevents complex formation, while modification of upper-strand G-33 has no detectable effect. At galP1, which lacks a consensus -35 region, modification of lower-strand G-33 and upper-strand G-14 reduces, but does not prevent, complex formation. G-33 is the only guanine residue in the -35 region of galP1 where modification interferes with open-complex formation. Since this guanine residue is not protected in open complexes, we conclude that its modification causes alteration of, or interference with, a transient contact during the transcription initiation pathway.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Composition
  • Base Sequence
  • Consensus Sequence
  • DNA Mutational Analysis
  • DNA, Bacterial / genetics*
  • DNA, Bacterial / metabolism
  • DNA-Directed RNA Polymerases / metabolism*
  • Escherichia coli / enzymology
  • Escherichia coli / genetics*
  • Galactose / metabolism
  • Guanine
  • Lac Operon / genetics*
  • Methylation
  • Molecular Sequence Data
  • Promoter Regions, Genetic / genetics*
  • Structure-Activity Relationship
  • Transcription, Genetic*


  • DNA, Bacterial
  • Guanine
  • DNA-Directed RNA Polymerases
  • Galactose