Pascal Arnoux, Christian Ruppelt, Flore Oudouhou, Jérôme Lavergne, Marina I. Siponen, René Toci, Ralf R. Mendel, Florian Bittner, David Pignol, Axel Magalon & Anne Walburger
Nature Communications, vol 6, Feb 4th (2015), http://dx.doi.org/10.1038/ncomms7148
Formate dehydrogenases (FDHs) are of interest as they are natural catalysts that sequester atmospheric CO2, generating reduced carbon compounds with possible uses as fuel. FDHs activity in Escherichia coli strictly requires the sulphurtransferase EcFdhD, which likely transfers sulphur from IscS to the molybdenum cofactor (Mo-bisPGD) of FDHs. Here we show that EcFdhDbinds Mo-bisPGD in vivo and has submicromolar affinity for GDP—used as a surrogate of the molybdenum cofactor’s nucleotide moieties. The crystal structure of EcFdhD in complex with GDPshows two symmetrical binding sites located on the same face of the dimer. These binding sites are connected via a tunnel-like cavity to the opposite face of the dimer where two dynamic loops, each harbouring two functionally important cysteine residues, are present. On the basis of structure-guided mutagenesis, we propose a model for the sulphuration mechanism of Mo-bisPGD where the sulphur atom shuttles across the chaperone dimer.