Electron crystallography of the scrapie prion protein complexed with heavy metals

Abstract

The insolubility of the disease-causing isoform of the prion protein (PrP Sc) has prevented studies of its three-dimensional structure at atomic resolution. Electron crystallography of two-dimensional crystals of N-terminally truncated PrP Sc (PrP 27–30) and a miniprion (PrP Sc106) provided the first insights at intermediate resolution on the molecular architecture of the prion. Here, we report on the structure of PrP 27–30 and PrP Sc106 negatively stained with heavy metals. The interactions of the heavy metals with the crystal lattice were governed by tertiary and quaternary structural elements of the protein as well as the charge and size of the heavy metal salts. Staining with molybdate anions revealed three prominent densities near the center of the trimer that forms the unit cell, coinciding with the location of the β-helix that was proposed for the structure of PrP Sc. Differential staining also confirmed the location of the internal deletion of PrP Sc106 at or near these densities.