Zinc significantly changes the aggregation pathway and the conformation of aggregates of human prion protein

• Fibril formation of prion protein (PrP) is associated with prion diseases.
• Wild-type PrP forms mature fibrils without zinc but short-rod aggregates with zinc.
• Zinc significantly changes the aggregation pathway of wild-type PrP.
• Zinc also significantly changes the conformation of wild-type PrP aggregates.
• Our findings link PrP aggregation modified by zinc to pathogenesis of prion diseases.

Prion diseases are caused by the conformational change of cellular prion protein PrPC into pathological prion protein PrPSc. Here we study the effect of zinc on the aggregation and conformational change of human prion protein (PrP). As revealed by thioflavin T binding assays, Sarkosyl-soluble SDS-PAGE, and transmission electron microscopy, aggregation of wild-type PrP in the absence of Zn2 + undergoes four steps: amorphous aggregates, profibrils, mature fibrils, and fragmented fibrils. When the molar ratio of Zn2 + to PrP was 9:1, however, aggregation of wild-type PrP undergoes another pathway in which wild-type PrP forms oligomers quickly and then forms short-rod aggregates. Unlike wild-type PrP, the octarepeats deletion mutant PrPΔocta forms typical mature fibrils either with or without zinc. As evidenced by isothermal titration calorimetry, Fourier transform infrared spectroscopy, and proteinase K digestion assays, Zn2 + strongly binds to wild-type PrP monomers with the first binding constant exceeding 107 M− 1 under denaturing conditions, and changes the conformation of wild-type PrP aggregates remarkably, but weakly binds to PrPΔocta with binding affinity around 104 M− 1 and has no obvious effects on the conformation of PrPΔocta aggregates. Our data demonstrate that zinc significantly changes the aggregation pathway and the conformation of wild-type PrP aggregates mainly via interaction with its octarepeat region. Our findings could explain how zinc modifies pathological PrP conformation associated with prion diseases.