A bacteriophage switches between lytic and lysogenic life cycles. The AimR-AimP-AimX communication system is responsible for phage lysis-lysogeny decisions during the infection of Bacillus subtilis. AimX is a regulator biasing phage lysis, AimR is a transcription factor activating AimX expression, and AimP is an arbitrium peptide that determines phage lysogeny by deactivating AimR. A strain-specific mechanism for the lysis-lysogeny decisions is proposed in SPbeta and phi3T phages. That is, the arbitrium peptide of the SPbeta phage stabilizes the SPbeta AimR (spAimR) dimer, whereas the phi3T-derived peptide disassembles the phi3T AimR (phAimR) dimer into a monomer. Here, we find that phAimR does not undergo dimer-to-monomer conversion upon arbitrium peptide binding. Gel-filtration, static light scattering (SLS) and analytical ultracentrifugation (AUC) results show that phAimR is dimeric regardless of the presence of arbitrium peptide. Small-angle X-ray scattering (SAXS) reveals that the arbitrium peptide binding makes an extended dimeric conformation. Single-molecule fluorescence resonance energy transfer (smFRET) analysis reveals that the phAimR dimer fluctuates among two distinct conformational states, and each preexisting state is selectively recognized by the arbitrium peptide or the target DNA, respectively. Collectively, our biophysical characterization of the phAimR dynamics underlying specific target recognition provides new mechanistic insights into understanding lysis-lysogeny decisions in Bacillus phage phi3T.

中文翻译：

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AimR 采用预先存在的二聚体构象在杆菌噬菌体 phi3T 的裂解-溶原性决策中进行特异性靶标识别

噬菌体在裂解和溶原性生命周期之间切换。AimR-AimP-AimX 通信系统负责枯草芽孢杆菌感染期间的噬菌体裂解-溶原性决定. AimX 是一种调节偏向噬菌体裂解的调节剂，AimR 是一种激活 AimX 表达的转录因子，而 AimP 是一种通过使 AimR 失活来决定噬菌体溶原性的仲裁肽。在 SPbeta 和 phi3T 噬菌体中提出了裂解-溶原性决定的菌株特异性机制。也就是说，SPbeta 噬菌体的仲裁肽稳定了 SPbeta AimR (spAimR) 二聚体，而 phi3T 衍生肽将 phi3T AimR (phAimR) 二聚体分解成单体。在这里，我们发现 phAimR 在仲裁肽结合后不会发生二聚体到单体的转化。凝胶过滤、静态光散射 (SLS) 和分析超速离心 (AUC) 结果表明，无论仲裁肽是否存在，phAimR 都是二聚体。小角 X 射线散射 (SAXS) 揭示了仲裁肽结合形成了扩展的二聚体构象。单分子荧光共振能量转移 (smFRET) 分析表明，phAimR 二聚体在两种不同的构象状态之间波动，每种预先存在的状态分别被仲裁肽或靶 DNA 选择性识别。总的来说，我们对特定目标识别背后的 phAimR 动力学的生物物理表征为理解芽孢杆菌噬菌体 phi3T。