Manganese Binding to the Prion Protein

Marcus W Brazier,Paul Davies,Esmie Player,Frank Marken,John H Viles,David R Brown

doi:10.1074/jbc.m709820200

Marcus W Brazier, Paul Davies + Show 4 more

Open Access

https://doi.org/10.1074/jbc.m709820200

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Abstract

There is considerable evidence that the prion protein binds copper. However, there have also been suggestions that prion protein (PrP) binds manganese. We used isothermal titration calorimetry to identify the manganese binding sites in wild-type mouse PrP. The protein showed two manganese binding sites with affinities that would bind manganese at concentrations of 63 and 200 mum at pH 5.5. This indicates that PrP binds manganese with affinity similar to other known manganese-binding proteins. Further study indicated that the main manganese binding site is associated with His-95 in the so-called "fifth site" normally associated with copper binding. Additionally, it was shown that occupancy by copper does not prevent manganese binding. Under these conditions, manganese binding resulted in an altered conformation of PrP, displacement of copper, and altered redox chemistry of the metal-protein complex. Cyclic voltammetric measurements suggested a complex redox chemistry involving manganese bound to PrP, whereas copper-bound PrP was able to undergo fully reversible electron cycling. Additionally, manganese binding to PrP converted it to a form able to catalyze aggregation of metal-free PrP. These results further support the notion that manganese binding could cause a conformation change in PrP and trigger changes in the protein similar to those associated with prion disease.

Highlights

Radic forms such as scrapie and Creutzfeldt-Jakob disease, inherited forms such as fatal familial insomnia and transmitted forms such as bovine spongiform encephalopathy and variant Creutzfeldt-Jakob disease
As well as possible beneficial effects of copper binding, other data suggest that inappropriate interactions between copper and prion protein (PrP) result in the aggregation of the protein and increased proteinase K resistance [16, 17]
We showed that the main manganese binding center of the protein is associated with a histidine a position 95 in the mouse PrP sequence with an affinity equivalent to that of other known manganese-binding proteins

Summary

Introduction

Radic forms such as scrapie and Creutzfeldt-Jakob disease, inherited forms such as fatal familial insomnia and transmitted forms such as bovine spongiform encephalopathy and variant Creutzfeldt-Jakob disease. As well as possible beneficial effects of copper binding, other data suggest that inappropriate interactions between copper and PrP result in the aggregation of the protein and increased proteinase K resistance [16, 17]. Manganese-bound PrP shows greater protease resistance [27], increased ␤-sheet content, the ability to aggregate [28], and the ability to seed polymerization of further prion protein [26]. These effects are observed in recombinant protein and protein expressed in cells [29]. We showed that the main manganese binding center of the protein is associated with a histidine a position 95 in the mouse PrP sequence with an affinity equivalent to that of other known manganese-binding proteins

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Conclusion