Tagged: X-ray

Sulfur shuttling across a chaperone during molybdenum cofactor maturation

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.