Dataset Information

Receptor recognition of transferrin bound to lanthanides and actinides: a discriminating step in cellular acquisition of f-block metals.

ABSTRACT: Following an internal contamination event, the transport of actinide (An) and lanthanide (Ln) metal ions through the body is facilitated by endogenous ligands such as the human iron-transport protein transferrin (Tf). The recognition of resulting metallo-transferrin complexes (M2Tf) by the cognate transferrin receptor (TfR) is therefore a critical step for cellular uptake of these metal ions. A high performance liquid chromatography-based method has been used to probe the binding of M2Tf with TfR, yielding a direct measurement of the successive thermodynamic constants that correspond to the dissociation of TfR(M2Tf)2 and TfR(M2Tf) complexes for Fe(3+), Ga(3+), La(3+), Nd(3+), Gd(3+), Yb(3+), Lu(3+), (232)Th(4+), (238)UO2(2+), and (242)Pu(4+). Important features of this method are (i) its ability to distinguish both 1 : 1 and 1 : 2 complexes formed between the receptor and the metal-bound transferrin, and (ii) the requirement for very small amounts of each binding partner (<1 nmol of protein per assay). Consistent with previous reports, the strongest receptor affinity is found for Fe2Tf (Kd1 = 5 nM and Kd2 = 20 nM), while the lowest affinity was measured for Pu2Tf (Kd1 = 0.28 ?M and Kd2 = 1.8 ?M) binding to the TfR. Other toxic metal ions such as Th(IV) and U(VI), when bound to Tf, are well recognized by the TfR. Under the described experimental conditions, the relative stabilities of TfR:(MxTf)y adducts follow the order Fe(3+) >> Th(4+) ~ UO2(2+) ~ Cm(3+) > Ln(3+) ~ Ga(3+) >>> Yb(3+) ~ Pu(4+). This study substantiates a role for Tf in binding lanthanide fission products and actinides, and transporting them into cells by receptor-mediated endocytosis.

SUBMITTER: Deblonde GJ

PROVIDER: S-EPMC3672314 | biostudies-literature | 2013 Jun

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Receptor recognition of transferrin bound to lanthanides and actinides: a discriminating step in cellular acquisition of f-block metals.

Deblonde Gauthier J-P GJ Sturzbecher-Hoehne Manuel M Mason Anne B AB Abergel Rebecca J RJ

Metallomics : integrated biometal science 20130601 6

Following an internal contamination event, the transport of actinide (An) and lanthanide (Ln) metal ions through the body is facilitated by endogenous ligands such as the human iron-transport protein transferrin (Tf). The recognition of resulting metallo-transferrin complexes (M2Tf) by the cognate transferrin receptor (TfR) is therefore a critical step for cellular uptake of these metal ions. A high performance liquid chromatography-based method has been used to probe the binding of M2Tf with Tf ...[more]

PMID: 23446908

Similar Datasets

Project description:Separation of lanthanides (Ln) from actinides (An) is unanimously challenging in reprocessing used nuclear fuel despite of much dedicated efforts over the past several decades. The TALSPEAK process is the current reference method in the United States for Ln3+/An3+ separation but suffers from several limitations, such as a narrow working pH window (3.5-4.0), costly pH buffers, and slow extraction kinetics. Studies aiming at improving TALSPEAK have so far focused on polyaminocarboxylates hold-back reagents. Here, a new class of water-soluble ligands comprising hydroxypyridinone metal-binding units are evaluated for Ln3+/An3+ separation. The model octadentate chelator 3,4,3-LI(1,2-HOPO) (abbreviated as HOPO) was used in combination with several industry-relevant organic extractants to separate Gd from four transplutonium elements (Am, Cm, Bk, and Cf). Cyanex 301 GN and HDEHP worked best in combination with HOPO, whereas HEH[EHP], Cyanex 572, and ACORGA M5640 did not yield practical Ln3+/An3+ separation. Separation factors between Gd3+ and Am3+ reach about 50 with the HOPO/Cyanex 301 GN system and 30 with the HOPO/HDEHP system. The results using HDEHP (SFGd/Am = 30, SFGd/Cm = 8.5, and SFGd/Cf = 773) are high enough for industrial applications, and the proposed system works at pH values as low as 1.5, which simplifies the process by eliminating the need for pH buffers. In contrast to previously proposed methods, the HOPO-based process is also highly selective at separating Bk from Ln3+ (SFGd/Bk = 273) owing to in situ, spontaneous oxidation of Bk(III) to Bk(IV) by HOPO. The optimal pH in the case of HOPO/Cyanex 301 GN is 3.6 (SFAm/Gd = 50, SFCm/Gd = 23, SFBk/Gd = 1.4, and SFCf/Gd = 3.2), but this system has the advantage of extracting An ions into the organic phase while keeping Ln ions in the aqueous phase, which is opposite to the conventional TALSPEAK process. This study represents the first optimization of a TALSPEAK-like Ln/An separation method using a HOPO chelator and paves the avenue for further developments of analytical science and reprocessing of used nuclear fuel.

Project description:The xanthine oxidoreductase (XOR) family are metal-containing enzymes that use the molybdenum cofactor (Moco), 2Fe-2S clusters, and flavin adenine dinucleotide (FAD) for their catalytic activity. This large molybdoenzyme family includes xanthine, aldehyde, and CO dehydrogenases. XORs are widely distributed from bacteria to humans due to their key roles in the catabolism of purines, aldehydes, drugs, and xenobiotics, as well as interconversions between CO and CO2. Assessing the effect of excess metals on the Rubrivivax gelatinosus bacterium, we found that exposure to copper (Cu) or cadmium (Cd) caused a dramatic decrease in the activity of a high-molecular-weight soluble complex exhibiting nitroblue tetrazolium reductase activity. Mass spectrometry and genetic analyses showed that the complex corresponds to a putative CO dehydrogenase (pCOD). Using mutants that accumulate either Cu+ or Cd2+ in the cytoplasm, we show that Cu+ or Cd2+ is a potent inhibitor of XORs (pCOD and the xanthine dehydrogenase [XDH]) in vivo. This is the first in vivo demonstration that Cu+ affects Moco-containing enzymes. The specific inhibitory effect of these compounds on the XOR activity is further supported in vitro by direct addition of competing metals to protein extracts. Moreover, emphasis is given on the inhibitory effect of Cu on bovine XOR, showing that the XOR family could be a common target of Cu. Given the conservation of XOR structure and function across the tree of life, we anticipate that our findings could be transferable to other XORs and organisms. IMPORTANCE The high toxicity of Cu, Cd, Pb, As, and other metals arises from their ability to cross membranes and target metalloenzymes in the cytoplasm. Identifying these targets provides insights into the toxicity mechanisms. The vulnerability of metalloenzymes arises from the accessibility of their cofactors to ions. Accordingly, many enzymes whose cofactors are solvent exposed are likely to be targets of competing metals. Here, we describe for the first time, with in vivo and in vitro experiments, a direct effect of excess Cu on the xanthine oxidoreductase family (XOR/XDH/pCOD). We show that toxic metal affects these Moco enzymes, and we suggest that access to the Moco center by Cu ions could explain the Cu inhibition of XORs in living organisms. Human XOR activity is associated with hyperuricemia, xanthinuria, gout arthritis, and other diseases. Our findings in vivo highlight XOR as a Cu target and thus support the potential use of Cu in metal-based therapeutics against these diseases.

Dataset Information

Receptor recognition of transferrin bound to lanthanides and actinides: a discriminating step in cellular acquisition of f-block metals.

Publications

Receptor recognition of transferrin bound to lanthanides and actinides: a discriminating step in cellular acquisition of f-block metals.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets