You are here : Home > The lab > Mechanistic studies of iron-sulfur cluster assembly in Escherichia coli: Which role for SufA?

Maïté Sendra

Mechanistic studies of iron-sulfur cluster assembly in Escherichia coli: Which role for SufA?

Published on 4 October 2007

Thesis presented October 04, 2007

[Fe-S] proteins are ubiquitous enzymes which play key roles within all living organisms. The biosynthetic process by which iron and sulfur atoms are combined in a controlled way into target proteins requires complex machineries. Among them, we can find the SUF machinery which is involved under oxidative stress and iron starvation conditions. This system is composed of six genes sufABCDSE. The SufA protein is described as a scaffold protein which is able to assemble transient [Fe-S] clusters and to transfer them to target apoproteins. Moreover, SufA contains three conserved cysteine residues which are proposed to be the ligands of the [Fe-S] clusters.
SufA is purified mainly in apo form. The [Fe-S] cluster can be reconstituted chemically in vitro. Under these conditions, SufA contains a mix of [2Fe-2S] clusters and [4Fe-4S] clusters. We isolated the native SufA protein in a metalled form after purification from the suf operon in anaerobic conditions. We showed that SufA contains an [Fe-S] cluster, probably a [2Fe-2S] cluster, which can be transferred to the ferredoxin efficiently. We also studied the molecular mechanisms of the assembly of [Fe-S] cluster in SufA. SufA is able to bind both sulfur atoms, coordinated by the three conserved cysteines, and iron atoms, mainly coordinated by nitrogen and oxygen ligands. These two elements can be used for the assembly of [Fe-S] clusters in the presence of a reductant. Lastly, we carried out preliminary in vitro experiments with site-directed mutant proteins to determine the ligands of [Fe-S] clusters in SufA, but today, the nature of the ligands remains unclear.

Biosynthesis, [Fe-S] clusters, scaffold protein, SufA, ligands

Download this thesis.