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Antirestriction Protein ArdB (R64) Interacts with DNA

A. A. Kudryavtseva1,a*, I. S. Okhrimenko1, V. S. Didina1, G. B. Zavilgelsky2, and I. V. Manukhov1,2

1Moscow Institute of Physics and Technology, 141707 Dolgoprudny, Moscow Region, Russia

2State Research Institute of Genetics and Selection of Industrial Microorganisms, Kurchatov Institute National Research Center, 117545 Moscow, Russia

* To whom correspondence should be addressed.

Received November 15, 2019; Revised January 14, 2020; Accepted January 17, 2020
The antirestriction ArdB protein inhibits the endonuclease activity of type I restriction/modification (RM) systems in vivo; however, the mechanism of inhibition remains unknown. In this study, we showed that recombinant ArdB from Escherichia coli cells co-purified with DNA. When overexpressed in E. coli cells, a portion of ArdB protein formed insoluble DNA-free aggregates. Only native ArdB, but not the ArdBΔD141 mutant lacking the antirestriction activity, co-purified with DNA upon anion-exchange and affinity chromatography or total DNA isolation from formaldehyde-treated cells. These observations confirm the hypothesis that ArdB blocks DNA translocation via the R subunits of the R2M2S complex of type I RM enzymes.
KEY WORDS: antirestriction, transmissible plasmid, R64, ArdB

DOI: 10.1134/S0006297920030074