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Biosynthesis of iron-sulphur clusters in chloroplasts


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Using complementary approaches, the Biocatalysis team at the Chemistry and Biology of Metals Laboratory​ and the team directed by M. Pilon (Fort Collins, USA) have characterized two novel SufE proteins (SufE2 and SufE3) in Arabidopsis thaliana chl​oroplasts.

Published on 19 November 2007

Iron-sulfphur (Fe-S) clusters are among the oldest-known prosthetics groups found in living organisms. They do not form spontaneously in vivo, but are generated by a tightly regulated biosynthetic process that brings a complex protein system into play. The SufE protein is part of such a system and acts as a sulfphur-transporter in Escherichai coli.

Using complementary approaches, the « Biocatalysis » team at the Laboratory of Metals in Chemistry and Biology and the team directed by M. Pilon (Programs in Molecular Plant Biology, Fort Collins, USA) have characterized two novel SufE proteins (SufE2 and SufE3) in Arabidopsis thaliana chloroplasts. The SufE3 protein is particularly interesting as it comprises 2 domains, one "SufE-like" domain and one "quinolinate synthase" (NadA) domain giving it a dual activity: production of sulfphur via the SufE domain and production of quinolinate, a fundamental intermediate in NAD biosynthesis, a vital biological cofactor, via the NadA domain. Quinolinate synthase activity depends on the presence of a cluster [4Fe-4S] situated located at the NadA domain. This is the first time that an iron-sulfphur protein (NadA - A. thaliana) has been identified as possessing an intrinsic activity that enables it to assemble and (or) repair its iron-sulphur cluster.


It is easy to understand why such a combination would be necessary in an 'oxidising' cell compartment such as a chloroplast, which does not generally promote continued activity of iron-sulphur proteins.

These findings were published as « Paper of the Week » 
[1] .

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