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The NMR structures of the recombinant prion proteins from chicken (Gallus gallus; chPrP), the red-eared slider turtle (Trachemys scripta; tPrP), and the African clawed frog (Xenopus !aevis; xlPrP) are presented. The amino acid sequences of these prion proteins show ∼30% identity with mammalian prion proteins. All three species form the same molecular architecture as mammalian PrPc, with a long, flexibly disordered tail attached to the N-terminal end of a globular domain. The globular domain in chPrP and tPrP contains three α-helices, one short 310-helix, and a short antiparallel β-sheet. In xlPrP, the globular domain includes three a-helices and a somewhat longer fl-sheet than in the other species. The spatial arrangement of these regular secondary structures coincides closely with that of the globular domain in mammalian prion proteins. Based on the low sequence identity to mammalian PrPs, comparison of chPrP, tPrP, and xlPrP with mammalian PrV structures is used to identify a set of essential amino acid positions for the preservation of the same PrPc fold in birds, reptiles, amphibians, and mammals. There are additional conserved residues without apparent structural roles, which are of interest for the ongoing search for physiological functions of PrPc in healthy organisms. [ABSTRACT FROM AUTHOR]

The NMR structures of the recombinant cellular form of the prion proteins (PrP9 of the cat (Felis catus), dog (canis familiaris), and pig (Sus scrofa), and of two polymorphic forms of the prion protein from sheep (Ovis aries) are presented In all of these species. PrV consists of an N-terminal flexibly extended tail with ∼100 amino acid residues and a C-terminal globular domain of ∼100 residues with three a-helices and a short antiparallel β-sheet. Although this global architecture coincides with the previously reported murine, Syrian hamster, bovine, and human PrV structures, there are local differences between the globular domains of the different species. Because the five newly determined PrPC structures originate from species with widely different transmissible spongiform encephalopathy records, the present data indicate previously uncharacterized possible correlations between local features in PrPC three- dimensional structures and susceptibility of different mammalian species to transmissible spongiform encephalopathies. [ABSTRACT FROM AUTHOR]