Cadmium-113 and carbon-13 NMR of cadmium(II) transferrins

Abstract

The cadmium(II) derivatives of ovotransferrin and human serum transferrin have been investigated through {sup 113}Cd and {sup 13}C NMR spectroscopy. A sharp {sup 113}Cd signal due to the bound Cd(II) ion is observed at 21.6 and 11.7 ppM for ovotransferrin and human serum transferrin, respectively. These chemical shift values are consistent with the involvement of only one histidine in each metal-binding set of the protein, as indicated by the recent x-ray structure of human lactoferrin. In the {sup 13}C NMR spectra the protein-bound carbonate signal is found in both cases at 168.2 ppM, and it clearly splits into a doublet (J {approximately} 20 Hz) when the protein contains {sup 113}Cd-enriched cadmium, thus giving further evidence of direct metal-carbonate binding. The addition of the nonsynergistic anion perchlorate to the ovotransferrin derivative resulted in the removal of the bound cadmium. 29 refs., 5 figs.