Mechanistic insights into metal ion activation and operator recognition by the ferric uptake regulator.

Zengqin Deng,Zhongzhou Chen,Tsu-Pei Chiu,Chong Feng,Remo Rohs,Qi Zhang,Qing Wang,Xu Wang,Ana Carolina Dantas Machado,Ying Li,Zhao Liu,Xiaorong Li,Jiangge Zheng,Xinmei Huo,Xiaoxuan Qi,Manfeng Zhang,Lei Qi,Lin Yu,Wei Wu

doi:10.1038/ncomms8642

Abstract

Ferric uptake regulator (Fur) plays a key role in the iron homeostasis of prokaryotes, such as bacterial pathogens, but the molecular mechanisms and structural basis of Fur–DNA binding remain incompletely understood. Here, we report high-resolution structures of Magnetospirillum gryphiswaldense MSR-1 Fur in four different states: apo-Fur, holo-Fur, the Fur–feoAB1 operator complex and the Fur–Pseudomonas aeruginosa Fur box complex. Apo-Fur is a transition metal ion-independent dimer whose binding induces profound conformational changes and confers DNA-binding ability. Structural characterization, mutagenesis, biochemistry and in vivo data reveal that Fur recognizes DNA by using a combination of base readout through direct contacts in the major groove and shape readout through recognition of the minor-groove electrostatic potential by lysine. The resulting conformational plasticity enables Fur binding to diverse substrates. Our results provide insights into metal ion activation and substrate recognition by Fur that suggest pathways to engineer magnetotactic bacteria and antipathogenic drugs.

Highlights

Ferric uptake regulator (Fur) plays a key role in the iron homeostasis of prokaryotes, such as bacterial pathogens, but the molecular mechanisms and structural basis of Fur–DNA binding remain incompletely understood
This study demonstrated that fur can directly regulate the expression of several key genes involved in iron transport and oxygen metabolism, and that fur can complement a fur-defective mutant of E. coli in an ironresponsive manner in vivo[19,20]
To determine the specific Fur-binding sequences, DNase I footprinting of the feoAB1 promoter was performed in the presence of manganese ions

Summary

Introduction

Ferric uptake regulator (Fur) plays a key role in the iron homeostasis of prokaryotes, such as bacterial pathogens, but the molecular mechanisms and structural basis of Fur–DNA binding remain incompletely understood. Fur, which was first discovered in Escherichia coli, is a global transcriptional regulator that directly controls the transcription of over 90 genes involved in iron uptake, storage and metabolism[6]. The molecular mechanisms for metal ion activation and operator recognition by Fur remained poorly understood. This study demonstrated that fur can directly regulate the expression of several key genes involved in iron transport and oxygen metabolism, and that fur can complement a fur-defective mutant of E. coli in an ironresponsive manner in vivo[19,20]. The fur gene plays a key role in the formation of magnetosomes, which are uniform, nanosized and membrane-enclosed magnetic crystals that have been used in many biomedical applications due to their unique features[21]

Methods

Results

Conclusion