X- Ray Structural, Functional And Computational Studies Of The O2-Sensitive E. Coli Hydrogenase-1 C19g Variant Reveal An Unusual [ 4fe-4s] Cluster+

The crystal structure of the Escherichia coli O-2-sensitive C19G [NiFe]-hydrogenase-1 variant shows that the mutation results in a novel FeS cluster, proximal to the Ni-Fe active site. While the proximal cluster of the native O-2-tolerant enzyme can transfer two electrons to that site, EPR spectroscopy shows that the modified cluster can transfer only one electron, this shortfall coinciding with O-2 sensitivity. Computational studies on electron transfer help to explain how the structural and redox properties of the novel FeS cluster modulate the observed phenotype.