Molecular mechanism of the dual regulation of bacterial iron sulfur cluster biogenesis by CyaY and IscX

AbstractIscX (or YfhJ) is a protein of unknown function which takes part in the iron-sulfur cluster assembly machinery, a highly specialised and essential metabolic pathway. IscX binds to iron with low affinity and interacts with IscS, the desulfurase central to cluster assembly. Previous studies have suggested a competition between IscX and CyaY, the bacterial ortholog of frataxin, for the same binding surface of IscS. This competition could suggest a link between the two proteins with a functional significance. Using a hybrid approach, we show here that IscX is a modulator of the inhibitory properties of CyaY: by competing for the same site on IscS, the presence of IscX rescues the rates of enzymatic cluster formation which are inhibited by CyaY. The effect is stronger at low iron concentrations, whereas it becomes negligible at high iron concentrations. These results strongly suggest that iron-sulfur cluster assembly is an exquisite example of an enzymatic process which requires a double regulation under the control of iron as the effector.

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A novel role of the mitochondrial iron-sulfur cluster assembly protein ISCU-1/ISCU in longevity and stress response

GeroScience ◽

10.1007/s11357-021-00327-z ◽

2021 ◽

Author(s):

Yi Sheng ◽

Guang Yang ◽

Kaitlyn Casey ◽

Shayla Curry ◽

Mason Oliver ◽

...

Keyword(s):

Stress Response ◽

Cluster Assembly ◽

Iron Sulfur Cluster ◽

Sulfur Cluster ◽

Iron Sulfur ◽

Mitochondrial Iron

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Multiple Sense and Antisense Promoters Contribute to the Regulated Expression of the isc-suf Operon for Iron-Sulfur Cluster Assembly in Rhodobacter

Microorganisms ◽

10.3390/microorganisms7120671 ◽

2019 ◽

Vol 7 (12) ◽

pp. 671 ◽

Cited By ~ 1

Author(s):

Xin Nie ◽

Bernhard Remes ◽

Gabriele Klug

Keyword(s):

Rhodobacter Sphaeroides ◽

Photosynthetic Electron Transport ◽

Regulatory Proteins ◽

Cluster Assembly ◽

Iron Sulfur Cluster ◽

Iron Sulfur Clusters ◽

Sulfur Cluster ◽

Iron Sulfur ◽

Photosynthetic Complexes ◽

The One

A multitude of biological functions relies on iron-sulfur clusters. The formation of photosynthetic complexes goes along with an additional demand for iron-sulfur clusters for bacteriochlorophyll synthesis and photosynthetic electron transport. However, photooxidative stress leads to the destruction of iron-sulfur clusters, and the released iron promotes the formation of further reactive oxygen species. A balanced regulation of iron-sulfur cluster synthesis is required to guarantee the supply of this cofactor, on the one hand, but also to limit stress, on the other hand. The phototrophic alpha-proteobacterium Rhodobacter sphaeroides harbors a large operon for iron-sulfur cluster assembly comprising the iscRS and suf genes. IscR (iron-sulfur cluster regulator) is an iron-dependent regulator of isc-suf genes and other genes with a role in iron metabolism. We applied reporter gene fusions to identify promoters of the isc-suf operon and studied their activity alone or in combination under different conditions. Gel-retardation assays showed the binding of regulatory proteins to individual promoters. Our results demonstrated that several promoters in a sense and antisense direction influenced isc-suf expression and the binding of the IscR, Irr, and OxyR regulatory proteins to individual promoters. These findings demonstrated a complex regulatory network of several promoters and regulatory proteins that helped to adjust iron-sulfur cluster assembly to changing conditions in Rhodobacter sphaeroides.

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