title: Structural Environment and Stability of the Complexes Formed Between Calmodulin and Actinyl Ions.
abstract: Because of their presence in the nuclear fuel cycle, neptunium and uranium are two actinides of main interest in case of internal contamination. Complexation of U(VI) and Np(V) by the target protein calmodulin (CaM(WT)) was therefore studied herein. Both actinides have two axial oxygen atoms, which, charge aside, makes them very similar structurally wise. This work combines spectroscopy and theoretical density functional theory (DFT) calculations. Structural characterization was performed by extended X-ray absorption fine structure (EXAFS) at the L(III)-edge for each studied actinide. Models for the binding site of the protein were developed and then refined by using DFT to fit the obtained experimental EXAFS data. The effect of hydrolysis was also considered for both actinides (the uranyl experiment was performed at pH 3 and 6, while the neptunyl experiment was conducted at pH 7 and 9). The effect of the pH variation was apparent on the coordination sphere of the uranyl complexes, while the neptunyl complex characteristics remained stable under both studied conditions. The DFT calculations showed that at near physiological pH the complex formed by CaM(WT) with the neptunium ion is more stable than the one formed with uranyl.
authors.affiliation: Institut de Physique Nucléaire d'Orsay, CNRS-IN2P3, Université Paris-Sud, Université Paris-Saclay , 91405, Orsay, France.
authors.forename: Florian
authors.initials: F
authors.lastname: Brulfert
authors.affiliation: Institut de Physique Nucléaire d'Orsay, CNRS-IN2P3, Université Paris-Sud, Université Paris-Saclay , 91405, Orsay, France.
authors.forename: Samir
authors.initials: S
authors.lastname: Safi
authors.affiliation: Institut de Physique Nucléaire d'Orsay, CNRS-IN2P3, Université Paris-Sud, Université Paris-Saclay , 91405, Orsay, France.
authors.forename: Aurélie
authors.initials: A
authors.lastname: Jeanson
authors.affiliation: Institut de Physique Nucléaire d'Orsay, CNRS-IN2P3, Université Paris-Sud, Université Paris-Saclay , 91405, Orsay, France.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Martinez-Baez
authors.affiliation: Institut de Physique Nucléaire d'Orsay, CNRS-IN2P3, Université Paris-Sud, Université Paris-Saclay , 91405, Orsay, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Roques
authors.affiliation: CEA, IBEB, Laboratoire des Interactions Protéine Métal, Saint-Paul-lez-Durance, F-13108, France.|CNRS, UMR 7265 Biol Veget & Microbiol Environ, Saint-Paul-lez-Durance, F-13108, France.|Aix Marseille Université, BVME UMR7265 , Marseille, F-13284, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Berthomieu
authors.affiliation: MARS beamline, Synchrotron SOLEIL, Gif sur Yvette, France.
authors.forename: Pier-Lorenzo
authors.initials: PL
authors.lastname: Solari
authors.affiliation: CEA, IBEB, Laboratoire des Interactions Protéine Métal, Saint-Paul-lez-Durance, F-13108, France.|CNRS, UMR 7265 Biol Veget & Microbiol Environ, Saint-Paul-lez-Durance, F-13108, France.|Aix Marseille Université, BVME UMR7265 , Marseille, F-13284, France.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Sauge-Merle
authors.affiliation: Institut de Physique Nucléaire d'Orsay, CNRS-IN2P3, Université Paris-Sud, Université Paris-Saclay , 91405, Orsay, France.
authors.forename: Éric
authors.initials: É
authors.lastname: Simoni
mesh_terms: D008671:Actinoid Series Elements / Q000737:chemistry*; D002147:Calmodulin / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D056928:X-Ray Absorption Spectroscopy
chemical_list: D008671:Actinoid Series Elements; D002147:Calmodulin