The MerR family of transcriptional regulators includes a variety of bacterial cytoplasmic proteins that respond to a wide range of signals, including toxins, metal ions, and endogenous metabolites. Its best-characterized members share similar structural and functional features with the family founder, the mercury sensor MerR, although most of them do not respond to metal ions. The group of “canonical” MerR homologs displays common molecular mechanisms for controlling the transcriptional activation of their target genes in response to inducer signals. This includes the recognition of distinctive operator sequences located at suboptimal σ⁷⁰-dependent promoters. Interestingly, an increasing number of proteins assigned to the MerR family based on their DNA-binding domain do not match in structure, sequence, or mode of action with any of the canonical MerR-like regulators. Here, we analyzed several members of the family, including this last group. Based on a phylogenetic analysis, and similarities in structural/functional features and position of their target operators relative to the promoter elements, we propose to assign these “atypical/divergent” MerR regulators to a phylogenetically separated group. These atypical/divergent homologs represent a new class of transcriptional regulators with novel regulatory mechanisms.

中文翻译：

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多种多样的 MerR 转录调节因子家族

MerR 转录调节因子家族包括多种细菌细胞质蛋白，可对多种信号做出反应，包括毒素、金属离子和内源代谢物。其最典型的成员与家族创始人汞传感器 MerR 具有相似的结构和功能特征，尽管其中大多数对金属离子不产生响应。这组“典型”MerR 同源物表现出共同的分子机制，用于控制其靶基因响应诱导信号的转录激活。这包括识别位于次优 σ ⁷⁰依赖性启动子处的独特操纵子序列。有趣的是，越来越多的蛋白质根据其 DNA 结合域被分配到 MerR 家族，这些蛋白质在结构、序列或作用模式上与任何典型的 MerR 样调节因子都不匹配。在这里，我们分析了该家庭的几位成员，包括最后一组。基于系统发育分析，以及其目标操纵子相对于启动子元件的结构/功能特征和位置的相似性，我们建议将这些“非典型/分歧”MerR调节子分配给系统发育上分离的组。这些非典型/不同的同源物代表了一类具有新颖调节机制的新型转录调节因子。