Escherichia coli SlyD, More Than a Ni(II) Reservoir

SlyD interacts with HypB and contributes to nickel insertion during [NiFe]-hydrogenase biogenesis. Herein, we provide evidence of SlyD acting as a nickel storage determinant in Escherichia coli and show that this Ni(II) can be mobilized to HypB in vitro even under competitive conditions. Furthermore, SlyD enhances the GTPase activity of HypB, and acceleration of release of Ni(II) from HypB is more pronounced when HypB is GDP-bound. The data support a model in which a HypB-SlyD complex establishes communication between GTP hydrolysis and nickel delivery and provide insight into the role of the HypB SlyD complex during [NiFe]-hydrogenase biosynthesis.