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