The antirepressor of phage P1. Isolation and interaction with the C1 repressor of P1 and P7

FEBS Lett. 1993 Nov 15;334(2):165-9. doi: 10.1016/0014-5793(93)81705-5.


Two antirepressor proteins, Ant1 and Ant2, of molecular weight 42 and 32 kDa, respectively, are encoded by P1 as a single open reading frame, with the smaller protein initiating at an in-frame start codon. Another open reading frame, icd, 5' upstream of and overlapping ant1 is required for ant1 expression. Using appropriate ant gene-carrying plasmids we have overproduced and purified Ant1/2 in the form of a protein complex and Ant2 as a single protein. Sequence analysis confirmed the N-terminal amino acids predicted from the DNA sequence of ant1/ant2, except that the N-terminal methionine is missing in the Ant2 protein. Under appropriate conditions the C1 repressors of phages P1 and P7 specifically co-precipitate with the Ant1/2 complex but not with Ant2 protein alone. The results suggest that the antirepressor may exert its C1-inactivating function by a direct protein-protein interaction.

MeSH terms

  • Amino Acid Sequence
  • Bacteriophage P1 / genetics
  • Bacteriophage P1 / metabolism*
  • Base Sequence
  • Coliphages / genetics
  • Coliphages / metabolism*
  • Electrophoresis, Polyacrylamide Gel
  • Escherichia coli / genetics
  • Escherichia coli / metabolism*
  • Molecular Sequence Data
  • Molecular Weight
  • Operon
  • Plasmids
  • Repressor Proteins / biosynthesis
  • Repressor Proteins / isolation & purification
  • Repressor Proteins / metabolism*
  • Restriction Mapping
  • Viral Proteins / biosynthesis
  • Viral Proteins / isolation & purification
  • Viral Proteins / metabolism*


  • Ant protein, Enterobacteria phage P22
  • Repressor Proteins
  • Viral Proteins