The manganese-responsive repressor Mur of Rhizobium leguminosarum is a member of the Fur-superfamily that recognizes an unusual operator sequence
The manganese-responsive repressor Mur of Rhizobium leguminosarum is a member of the Fur-superfamily that recognizes an unusual operator sequence
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DOI：
10.1099/mic.0.28342-0
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发表时间：
2005-12-01
期刊：
影响因子：
2.8
通讯作者：
Sawers, RG
中科院分区：
文献类型：
--
作者：
Díaz-Mireles, E;Wexler, M;Sawers, RG
豆根瘤菌的锰吸收调节因子 Mur 是整体铁调节蛋白 Fur 的密切同源物。 Mur 抑制 satABCD 操纵子，该操纵子编码 Mn2+ 转运系统，特别是响应 Mn2+ 而不是 Fe。在之前的工作中，作者绘制了两个坐操纵子转录本（称为 TS1 和 TS2）的 5' 末端，它们由 Mn2+-Mur 协调调节，但本文现在表明只有 TS1 是初级转录本。 DNase I 保护分析表明，纯化的 Mur 以相似的亲和力结合到 satABCD 调节区的两个位点，但仅当反应缓冲液中存在 Mn2+ 时才有效。这些 Mn2+-Mur 结合位点称为 MRS1 和 MRS2（Mur 响应序列），它们在序列上彼此密切相关，并且相距 16 bp，跨越转录起始位点 TS1。 MRS1 和 MRS2 的受保护 DNA 范围分别为 34 和 31 bp，这与 Fur 家族的其他成员一致。 Mn2+-Mur 识别的 DNA 序列与传统的 Fur 盒完全不同，但注意到与日本慢生根瘤菌的 Fur 调节剂的识别序列有一些相似之处。 R. leguminosarum mur 基因的转录分析显示其表达不依赖于 Mn2+-Mur。因此，Mur 是一种序列特异性 DNA 结合蛋白，在体外对锰做出反应，因此可以阻止 RNA 聚合酶接近 satABCD 启动子。此外，Mur 识别出 Fur 超家族的非典型 DNA 序列，并且像来自 B. japonicum 的 Fur 一样，定义了一个新的 Fur 样转录调节子亚类。
The manganese uptake regulator Mur of Rhizobium leguminosarum is a close homologue of the global iron regulatory protein Fur. Mur represses the sitABCD operon, which encodes a Mn2+ transport system, specifically in response to Mn2+ but not Fe. In previous work the authors mapped the 5' ends of two sit operon transcripts, termed TS1 and TS2, which were co-ordinately regulated by Mn2+-Mur, but this paper now shows that only TS1 is a primary transcript. DNase I protection analyses showed that purified Mur bound, with similar affinity, to two sites in the regulatory region of sitABCD, but only when Mn2+ was present in the reaction buffer. These Mn2+-Mur-binding sites, termed MRS1 and MRS2 (Mur-responsive sequence), were closely related in sequence to each other and were separated by 16 bp, spanning the transcription initiation site TS1. The extent of the protected DNA was 34 and 31 bp for MRS1 and MRS2, respectively, which is in accord with other members of the Fur family. The DNA sequences recognized by Mn2+-Mur are wholly different from conventional Fur boxes, but some similarities to a recognition sequence for the Fur regulator from Bradyrhizobium japonicum were noted. Transcription analysis of the R. leguminosarum mur gene showed its expression to be independent of Mn2+-Mur. Thus, Mur is a sequence-specific DNA-binding protein that responds in vitro to manganese, and thus can occlude RNA polymerase access to the sitABCD promoter. Moreover, Mur recognizes a DNA sequence atypical for the Fur superfamily and, like Fur from B. japonicum, defines a new subclass of Fur-like transcriptional regulators.