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Structural basis for regulation of rhizobial nodulation and symbiosis gene expression by the regulatory NolR

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The symbiosis between rhizobial microbes and host plants involves the coordinated expression of multiple genes, which leads to nodule formation and nitrogen fixation. As part of the transcriptional machinery for nodulation and symbiosis across a range of Rhizobium, NolR serves as a global regulatory protein. Here we present the x-ray crystal structures of NolR in the unliganded form and complexed with two different 22 base pair (bp) double-stranded operator sequences (oligos AT and AA). Structural and biochemical analysis of NolR reveals protein-DNA interactions with an asymmetric operator site and defines a mechanism for conformational switching of a key residue (Gln56) to accommodate variation in target DNA sequences from diverse rhizobial genes for nodulation and symbiosis. This conformational switching alters the energetic contributions to DNA binding without changes in affinity for the target sequence. A model for the role of NolR in the regulation of different nodulation and symbiosis genes is also proposed. These studies provide the first structural insight on the regulation of genes involved in the agriculturally and ecologically important symbiosis of microbes and plants that leads to nodule formation and nitrogen fixation.
Soon Goo Lee , Hari B. Krishnan , Joseph M. Jez
DNA , Rhizobium , crystal structure , gene expression , genes , host plants , microorganisms , models , nitrogen fixation , nodulation , nucleotide sequences , symbiosis , transcription factors
USDA Scientist Submission
Pnas 2014 v.111 no.17
Journal Articles, USDA Authors, Peer-Reviewed
Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.