1887

Abstract

The anganese ptake egulator Mur of is a close homologue of the global iron regulatory protein Fur. Mur represses the operon, which encodes a Mn transport system, specifically in response to Mn but not Fe. In previous work the authors mapped the 5′ ends of two operon transcripts, termed TS1 and TS2, which were co-ordinately regulated by Mn-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 , but only when Mn was present in the reaction buffer. These Mn-Mur-binding sites, termed MRS1 and MRS2 (ur-esponsive equence), 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 Mn-Mur are wholly different from conventional Fur boxes, but some similarities to a recognition sequence for the Fur regulator from were noted. Transcription analysis of the gene showed its expression to be independent of Mn-Mur. Thus, Mur is a sequence-specific DNA-binding protein that responds to manganese, and thus can occlude RNA polymerase access to the promoter. Moreover, Mur recognizes a DNA sequence atypical for the Fur superfamily and, like Fur from , defines a new subclass of Fur-like transcriptional regulators.

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2005-12-01
2019-11-20
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