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 ArdBAD141 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 R 2 M 2 S complex of type I RM enzymes.

中文翻译：

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抗限制蛋白 ArdB (R64) 与 DNA 相互作用

抗限制性 ArdB 蛋白在体内抑制 I 型限制/修饰 (RM) 系统的核酸内切酶活性；然而，抑制机制仍然未知。在这项研究中，我们展示了来自大肠杆菌细胞的重组 ArdB 与 DNA 共纯化。当在大肠杆菌细胞中过表达时，一部分 ArdB 蛋白形成了不溶性的无 DNA 聚集体。只有天然 ArdB，而不是缺乏抗限制活性的 ArdBAD141 突变体，通过阴离子交换和亲和层析或从甲醛处理的细胞中分离总 DNA 与 DNA 共纯化。这些观察证实了 ArdB 通过 I 型 RM 酶的 R 2 M 2 S 复合物的 R 亚基阻断 DNA 易位的假设。