Laboratory of Genetics of Bacteria, State Research Institute of Genetics and Selection of Industrial Microorganisms of the National Research Center "Kurchatov Institute", Moscow, Russia, 115454.
Molecular Genetics Lab, Moscow Institute of Physics and Technology, Dolgoprudny, Russia, 141700.
Curr Microbiol. 2019 Nov;76(11):1374-1378. doi: 10.1007/s00284-019-01755-z. Epub 2019 Aug 12.
Anti-restriction proteins ArdB/KlcA specifically inhibit restriction (endonuclease) activity of restriction-modification (RM) type I systems. Molecular mechanisms of ArdB/KlcA-based anti-restriction remain unknown. In this study, we quantitate effects of ArdB on protection of unmodified λ phage DNA from EcoKI restriction. After UV irradiations, which produce significant amounts of unmodified chromosomal DNA in Escherichia coli K12 cells, the protective activity of ArdB decreases. Unlike ArdB, DNA-mimicking protein Ocr retains its ability to protect the unmodified λ phage regardless of UV dose. We hypothesize that the observed decrease in ArdB protective activity in UV-treated cells is due to its binding to unmodified chromosomal DNA, which decreases effective concentrations of free ArdB molecules available for λ phage protection against type I restriction enzymes.
抗限制蛋白 ArdB/KlcA 特异性抑制限制（内切酶）修饰 I 型系统的限制活性。基于 ArdB/KlcA 的抗限制的分子机制尚不清楚。在这项研究中，我们定量研究了 ArdB 对未修饰 λ噬菌体 DNA 免受 EcoKI 限制的保护作用。在紫外线照射后，大肠杆菌 K12 细胞中会产生大量未修饰的染色体 DNA，ArdB 的保护活性会降低。与 ArdB 不同，DNA 模拟蛋白 Ocr 可以保留其保护未修饰 λ噬菌体的能力，而与紫外线剂量无关。我们假设，在紫外线处理的细胞中观察到的 ArdB 保护活性降低是由于其与未修饰的染色体 DNA 结合，从而降低了游离 ArdB 分子对 λ噬菌体免受 I 型限制酶限制的有效浓度。
