Antirestriction Protein ArdB (R64) Interacts with DNA

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A. A. Kudryavtseva^1,a*, I. S. Okhrimenko¹, V. S. Didina¹, G. B. Zavilgelsky², and I. V. Manukhov^1,2

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

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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.

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KEY WORDS: antirestriction, transmissible plasmid, R64, ArdB

DOI: 10.1134/S0006297920030074

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