Nickel Metalloregulators and Chaperones

Abstract

Nickel is essential for the survival of many pathogenic bacteria. E. coli and H. pylori require nickel for [NiFe]-hydrogenases. H. pylori also requires nickel for urease. At high concentrations nickel can be toxic to the cell, therefore, nickel concentrations are tightly regulated. Metalloregulators help to maintain nickel concentration in the cell by regulating the expression of the genes associated with nickel import and export. Nickel import into the cell, delivery of nickel to target proteins, and export of nickel from the cell is a very intricate and well-choreographed process. The delivery of nickel to [NiFe]-hydrogenase and urease is complex and involves several chaperones and accessory proteins. A combination of biochemical, crystallographic, and spectroscopic techniques has been utilized to study the structures of these proteins, as well as protein–protein interactions resulting in an expansion of our knowledge regarding how these proteins sense and bind nickel. In this review, recent advances in the field will be discussed, focusing on the metal site structures of nickel bound to metalloregulators and chaperones.

Evidence for a Putative Isoprene Reductase in Acetobacterium wieringae

“…The role of HypA and HypB during [NiFe]-hydrogenase maturation is well studied and first involves the metal-dependent (Ni 2+ ) dimerization of HypB with one equivalent of nickel per dimer ( 79 , 80 ). Second, the hydrolysis of GTP facilitates the transfer of Ni 2+ from HypB to HypA by weakening the binding affinity of Ni 2+ to HypB and promoting the formation of the HypAB heterodimer ( 81 ) or, in some organisms such as Thermococcus kodakarensis , a heterotetramer HypAABB ( 82 ). After the Ni 2+ is transferred to HypA, HypA dissociates from the complex and delivers the cofactor to the large subunit of the hydrogenase ( 50 , 83 ).…”

Synergistic Interaction between Symbiotic N2 Fixing Bacteria and Bacillus strains to Improve Growth, Physiological Parameters, Antioxidant Enzymes and Ni Accumulation in Faba Bean Plants (Vicia faba) under Nickel Stress

“…Nickel is required for the synthesis of hydrogenase in prokaryotes, which catalyzes the oxidation of hydrogen liberated by nitrogenase during the dinitrogen reduction process [ 15 ]. Nickelin (HypB), an accessory protein responsible for Ni supply in rhizobia, has a dual role in Ni mobilization into hydrogenase and Ni storage [ 16 ]. Metals have been shown to negatively affect microorganism growth, morphology, and activity, including symbiotic nitrogen fixation [ 17 ].…”

Bioinorganic Chemistry of Nickel

“…The knowledge of proteins involved in cellular nickel trafficking (metalloregulators and metallochaperones) is summarized by Higgins in a review [5], which is complemented by a second monographic article by Nim and Wong [6], that focuses more specifically on the maturation of the nickel enzyme urease as a paradigmatic example of how cells balance nickel essentiality and toxicity. These two reviews are augmented by two original research papers on this aspect of the nickel bioinorganic chemistry field: the paper by Alfano et al [7] is focused on CooJ, an accessory protein necessary for the maturation of the nickel-dependent enzyme carbon monoxide dehydrogenase, while the paper by Barchi and Musiani [8] describes the structure-function relationships in InrS, a nickel-dependent transcription factor from cyanobacteria.…”