7B5T image
Entry Detail
PDB ID:
7B5T
Keywords:
Title:
S. agalactiae BusR transcription factor
Biological Source:
Source Organism:
PDB Version:
Deposition Date:
2020-12-07
Release Date:
2021-08-11
Method Details:
Experimental Method:
Resolution:
2.80 Å
R-Value Free:
0.26
R-Value Work:
0.25
R-Value Observed:
0.25
Space Group:
I 4
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:GntR family transcriptional regulator
Chain IDs:A, B, C (auth: D), D (auth: C)
Chain Length:215
Number of Molecules:4
Biological Source:Streptococcus agalactiae
Modified Residue
Compound ID Chain ID Parent Comp ID Details 2D Image
MSE A MET modified residue
Primary Citation
BusR senses bipartite DNA binding motifs by a unique molecular ruler architecture.
Nucleic Acids Res. 49 10166 10177 (2021)
PMID: 34432045 DOI: 10.1093/nar/gkab736

Abstact

The cyclic dinucleotide second messenger c-di-AMP is a major player in regulation of potassium homeostasis and osmolyte transport in a variety of bacteria. Along with various direct interactions with proteins such as potassium channels, the second messenger also specifically binds to transcription factors, thereby altering the processes in the cell on the transcriptional level. We here describe the structural and biochemical characterization of BusR from the human pathogen Streptococcus agalactiae. BusR is a member of a yet structurally uncharacterized subfamily of the GntR family of transcription factors that downregulates transcription of the genes for the BusA (OpuA) glycine-betaine transporter upon c-di-AMP binding. We report crystal structures of full-length BusR, its apo and c-di-AMP bound effector domain, as well as cryo-EM structures of BusR bound to its operator DNA. Our structural data, supported by biochemical and biophysical data, reveal that BusR utilizes a unique domain assembly with a tetrameric coiled-coil in between the binding platforms, serving as a molecular ruler to specifically recognize a 22 bp separated bipartite binding motif. Binding of c-di-AMP to BusR induces a shift in equilibrium from an inactivated towards an activated state that allows BusR to bind the target DNA, leading to transcriptional repression.

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Primary Citation of related structures