Measurement of Altered Aspartyl Residues in the Scrapie Associated Form of Prion Protein

Copper(II)-induced Conformational Changes and Protease Resistance in Recombinant and Cellular PrP

“…This covalent change most likely occurs by a well known chemical pathway involving deamidation and hydrolysis. Although studies of a rapid-onset prion disease model found only 0.5 mol % D-aspartyl and L-isoaspartyl residues in PrP Sc , arguing against an obligatory relationship between deamidation and PrP Sc formation (35), our biochemical studies suggest a novel pathway for the formation of PrP Sc -like molecules perhaps germane to the origins of sporadic prion disease.…”

“…It has been argued that deamidation and racemization of asparagine residues do not comprise a crucial or obligatory determinant in formation of PrP Sc in rapid models of experimental scrapie disease, as stoichiometric elevations of altered aspartyl residues are absent from corresponding PrP Sc preparations (35). Thus, most likely, our findings do not address the fundamental mechanism of prion replication as it occurs in experimental prion disease.…”

“…In short, could covalent variants of the PrP backbone comprise strain determinants? Although it is established that PrP Sc from rapidly replicating prion strains such as 263K and Sc237 includes L-Asn-107 (35,88), more slowly replicating strains might encompass covalent derivatives of Asn-107 generated by rate-limiting deamidative pathways. Although these notions are currently speculative, our findings suggest that experiments to catalogue Asn derivatives in brain PrP and to create mutations at or in the vicinity of codon 107 may provide new insights into prion disease pathogenesis.…”

Biological Significance of Isoaspartate and Its Repair System

“…35) Recent studies have also reported the formation of isoaspartate in age-associated human neurodegenerative diseases. Isoaspartyl residues in the scrapie form of prions in the brains of mice infected with scrapie, 36) amyloid-b (Ab) peptide deposited on senile plaques in Alzheimer's disease (AD), [37][38][39][40] and tau in paired helical filaments of AD 41) have been found. It is still unclear, however, whether the isoaspartyl residues in these deposited proteins are the cause or the result of protein insolubility and toxicity in such pathological conditions.…”

Lysine hydroxylation and O-glycosylation in the globular, C-terminal region of mammalian-expressed, recombinant PrP

“…Thus, post translational modifications in this region of the protein may be more likely to impact on PrP folding/misfolding. There have been reports of oxidation of specific methionine residues [26] and a suggestion that asparagine/aspartate residues may be altered in PrP Sc [27,28]. In proof of principle studies, it has also been shown that conditions that cause oxidative or nitrative modifications, or that deiminate PrP, can lead to misfolding [29,30] and it is clear that any PTMs that can be detected in the C-terminal domain of PrP are candidates to impact adversely on protein folding.…”