Screening of Human Serum Proteins for Uranium Binding

Abstract

About 20% of uranyl ions in serum are associated with the protein pool. A few of them such as transferrin have been characterized, but most still have to be identified to obtain a better explanation of the biochemical toxicology and kinetics of uranium. We designed an in vitro sensitive procedure involving a combination of bidimensional chromatography with time-resolved fluorescence, coupled with proteomic analysis, to identify uranium-binding proteins in human serum fractions. Ten novel targets were identified and validated using purified proteins and inductively coupled plasma mass spectrometry. Of these, ceruloplasmin, hemopexin, and two complement proteins displayed the capacity to bind uranium with stoichiometry greater than 1 mole of uranium per mole of protein. Not all of these targets are metalloproteins, suggesting that uranyl ions can use a wide variety of binding sites and coordination strategies. These data provide additional insights into a better understanding of uranium chemical toxicity.

Spectroscopic study of the interaction of U(VI) with transferrin and albumin for speciation of U(VI) under blood serum conditions

“…It has been reported that U(VI) in the blood stream is forming complexes with carbonate and serum proteins, in particular with albumin and transferrin [7,[9][10][11]. The thermodynamic parameters describing the interaction between U(VI) and relevant low molecular weight inorganic and organic ligands have been extensively studied and are rather well known [12,13].…”

“…The thermodynamic parameters describing the interaction between U(VI) and relevant low molecular weight inorganic and organic ligands have been extensively studied and are rather well known [12,13]. However, the interaction between U(VI) and serum proteins is still a subject of discussion with respect to the nature of the interacting proteins [11,14], the quantitative description of the interaction [5] and the coordination environment of U(VI) [15], in particular with respect to the possible presence of the carbonate ion in the coordination sphere [7,14,15].…”

“…Based on these parameters and including literature data of thermodynamic constants of U(VI) complexation with low molecular weight organic and inorganic ligands, a model calculation was performed to describe U(VI) interactions in human blood serum in a bottom-up approach. The reliability of the simulation was assessed by comparison with published experimental in vitro speciation results [9,11,17]. To identify promising molecules for in vivo chelation of 230 U, the serum stability of several U(VI) chelate complexes was simulated.…”

On molecular recognition of an uranyl chelate by monoclonal antibodies

“…To establish human and environmental heavy metal toxicity thresholds, it is important to characterize the interactions between biological targets (e.g., proteins or DNA) and the soluble form of metals including actinides (Gorden et al, 2003). The uranyl ion (UO 2þ 2 ) is the most common species encountered in aqueous solutions of uranium (Ansoborlo et al, 2006;Pible et al, 2006) and is known to become incorporated in bones and tissues (Vidaud et al, 2005). In the study of tracing uranium chemicals in the body, we chose a model system where the uranyl ion can be specifically recognized by monoclonal antibodies.…”

An alternative view of the proposed alternative activities of hemopexin

“…1 and 2). This three-dimensional structure reveals that the Arg-GlyGlu sequence (residues 190-192) proposed above to act as a site for interaction with cell surfaces is highly exposed on the surface of the protein and near the JEN14 epitope [residues 123-143, which include the Arg-Gly-Glu sequence (128)(129)(130)] that was predicted to be one site recognized by the rabbit hemopexinheme receptor.…”