Distinct effects of Cu<sup>2+</sup>-binding on oligomerization of human and rabbit prion proteins

Abstract

The cellular prion protein (PrP(C)) is a kind of cell-surface Cu(2+)-binding glycoprotein. The oligomerization of PrP(C) is highly related to transmissible spongiform encephalopathies (TSEs). Cu(2+) plays a vital role in the oligomerization of PrP(C), and participates in the pathogenic process of TSE diseases. It is expected that Cu(2+)-binding has different effects on the oligomerization of TSE-sensitive human PrP(C) (HuPrP(C)) and TSE-resistant rabbit PrP(C) (RaPrP(C)). However, the details of the distinct effects remain unclear. In the present study, we measured the interactions of Cu(2+) with HuPrP(C) (91-230) and RaPrP(C) (91-228) by isothermal titration calorimetry, and compared the effects of Cu(2+)-binding on the oligomerization of both PrPs. The measured dissociation constants (Kd) of Cu(2+) were 11.1 ± 2.1 μM for HuPrP(C) and 21.1 ± 3.1 μM for RaPrP(C). Cu(2+)-binding promoted the oligomerization of HuPrP(C) more significantly than that of RaPrP(C). The far-ultraviolet circular dichroism spectroscopy experiments showed that Cu(2+)-binding induced more significant secondary structure change and increased more β-sheet content for HuPrP(C) compared with RaPrP(C). Moreover, the urea-induced unfolding transition experiments indicated that Cu(2+)-binding decreased the conformational stability of HuPrP(C) more distinctly than that of RaPrP(C). These results suggest that RaPrP(C) possesses a low susceptibility to Cu(2+), potentially weakening the risk of Cu(2+)-induced TSE diseases. Our work sheds light on the Cu(2+)-promoted oligomerization of PrP(C), and may be helpful for further understanding the TSE-resistance of rabbits.

Rational design of metalloenzymes: From single to multiple active sites

“…Heme proteins are a large class of metalloenzymes crucial for biological systems, which bind the heme group non-covalently such as heme b (Fe-protoporphyrin IX) or covalently such as heme c via thioether bonds and other heme-protein cross-links [127]. The heme b group can be removed from the protein scaffold under acidic conditions, producing the corresponding apo-proteins [128].…”

“…The chemical property of heme are strongly affected by its substitutions, especially those at the 2-and 4-positions, as in most post-translational modifications [127]. The modified heme analogs can then be used to fine-tune the property and function of heme enzymes.…”

Structural Consequences of Copper Binding to the Prion Protein

“…The effect of Cu(II)-binding was also assessed on the oligomerization of PrP C . Lin et al showed that Cu(II)-binding promoted oligomerization of a susceptible species more significantly than that of a resistant species, suggesting that the low susceptibility to Cu(II) in the resistant species might results in a weak risk of Cu(II)-induced TSE diseases [141]. In support to the role of the non-OR region for prion conversion, transgenic mice, TgPrP(H95G), with an amino acid replacement at residue H95 showed shorter disease progression than WT control mice and classical clinical signs of TSE [142].…”