Nickel trafficking proteins must be able to distinguish Ni from a pool of available metals in cells with similar physical and chemical properties in order to drive metal-specific biological responses and avoid crosstalk. The mechanisms involved in this ‘metal recognition’ are varied and not well known, although protein allosterics and redox-associated structural changes are known to play important roles in general. Recent advances in understanding mechanisms of "nickel recognition" will be the focus of the presentation. Examples will be drawn primarily from work on the Helicobacter pylori nickel metallochaperone, HypA, and the Ni- and Co-responsive E. Coli transcriptional regulator, RcnR. HypA is a Ni metallochaperone that supplies Ni to hydrogenases. However, in H. pylori, HypA plays a dual role and is essential for supplying Ni to urease as well as hydrogenase. The transcriptional regulator, RcnR, is a founding member of a new class of DNA binding proteins and differentially recognizes the two cognate metals. Using mutagenesis in tandem with X-ray absorption spectroscopy as a structural probe of metal sites, NMR and XRD as probes of protein structure, and assays that monitor Ni enzyme activity and H. pylori acid viability, as well as transcriptional response, several features of specific metal recognition by HypA and RcnR have been illuminated and will be discussed.

Metal selectivity in nickel trafficking proteins

253rd National Meeting (2017)

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