Interaction of bacteriophage T4 AsiA protein with Escherichia coli sigma70 and its variant

FEBS Lett. 1997 Jul 7;411(1):60-2. doi: 10.1016/s0014-5793(97)00668-6.


Bacteriophage T4 produces a small protein AsiA, which inhibits transcription from sigma70-dependent promoters in E. coli by tightly binding to sigma70 and is therefore termed as anti-sigma factor. We observed that there was no inhibition of single round transcription at lac UV5 promoter when AsiA was added to preformed open complex between RNA polymerase and template DNA. However, transcription was found to proceed normally at 'extended -10' promoters in the presence of AsiA. It appears therefore that AsiA binds sigma70 at its 4.2-subdomain or in its close vicinity. Further experiments on immunoprecipitation of sigma70 and a mutant sigma70-V576G with AsiA seem to corroborate such conclusion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacteriophage T4 / metabolism
  • DNA-Directed RNA Polymerases / metabolism*
  • Escherichia coli / metabolism
  • Mutagenesis, Site-Directed
  • Sigma Factor / metabolism*
  • Transcription, Genetic
  • Viral Proteins / metabolism*


  • AsiA protein, Enterobacteria phage T4
  • Sigma Factor
  • Viral Proteins
  • RNA polymerase sigma 70
  • DNA-Directed RNA Polymerases

Associated data

  • PDB/1AD2