[Comparative analysis of antirestriction activity of R64 ArdA and ArdB proteins].

Antirestriction proteins ArdA and ArdB are specific inhibitors of the type I restriction-modification enzymes. The transmissible plasmid R64 ardA and yfeB (ardB) genes were cloned in pUC18 and pZE21 vectors. It was shown that the R64 ArdA and ArdB proteins inhibit only restriction activity of the type I restriction-modification enzyme (EcoKI) in Escherichia coli K12 cells. The dependence of the effectiveness of the antirestriction activity of the ArdA and ArdB proteins on the intracellular concentration was determined. Antirestriction activity of ArdB is independent from the ClpXP protease. Transcription of yfeB (ardB) gene in R64 plasmid is realized from the yfeA promoter.