Investigation of the Plutonium(IV) Interactions with Two Variants of the EF-Hand Ca-Binding Site I of Calmodulin

Dueto its presence in the nuclear industry and its strongradiotoxicity,plutonium is an actinide of major interest in the event of internalcontamination. To improve the understanding of its mechanisms of transportand accumulation in the body, the complexation of Pu-(IV) to the mostcommon protein calcium-binding motif found in cells, the EF-hand motifof calmodulin, was investigated. Visible and X-ray absorption spectroscopies(XAS) in solution made it possible to investigate the speciation ofplutonium at physiological pH (pH 7.4) and pH 6 in two variants ofthe calmodulin Ca-binding site I and using Pu-(IV) in different media:carbonate, chloride, or nitrate solutions. Three different speciesof Pu were identified in the samples, with formation of 1:1 Pu-(IV):calmodulinpeptide complexes, Pu-(IV) reduction, and formation of peptide-mediatedPu-(IV) hexanuclear cluster. Toimprove the understanding of the transport and accumulationof plutonium in the body, the complexation of Pu-(IV) to the most commonprotein calcium-binding motif in cells, the EF-hand motif of calmodulin,was investigated. The plutonium speciation in the presence of twovariants of the calmodulin Ca binding site I was investigated by visibleand X-ray absorption spectroscopies (XAS). Different Pu species wereobserved, including 1:1 Pu-(IV):calmodulin complex, reduced Pu-(IV),and a Pu-(IV) hexanuclear cluster.

Automated summary

In order to enhance the understanding of the transport and accumulation mechanisms of plutonium in the body, the complexation of Pu-(IV) with the EF-hand motif of calmodulin, the most common protein calcium-binding motif in cells, was studied. The speciation of plutonium was investigated using visible and X-ray absorption spectroscopies (XAS) in solution at physiological pH (pH 7.4) and pH 6, with two variants of the calmodulin Ca binding site I, and in different media of carbonate, chloride, and nitrate solutions. Three different species of Pu were identified in the samples, including 1:1 Pu-(IV):calmodulin peptide complexes, Pu-(IV) reduction, and peptide-mediated Pu-(IV) hexanuclear clusters.