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Amyloid of Rnq1p, the Basis of the [PIN⁺] Prion, Has a Parallel In-Register β-Sheet Structure
Reed B. Wickner, Fred Dyda and Robert Tycko
Proceedings of the National Academy of Sciences of the United States of America
Vol. 105, No. 7 (Feb. 19, 2008), pp. 2403-2408
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/25451479
Page Count: 6
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The [PIN⁺] prion, a self-propagating amyloid form of Rnq1p, increases the frequency with which the [PSI⁺] or [URE3] prions arise de novo. Like the prion domains of Sup35p and Ure2p, Rnq1p is r̲ich in N̲ and Q̲ residues, but rnq1Δ strains have no known phenotype except for inability to propagate the [PIN⁺] prion. We used solid-state NMR methods to examine amyloid formed in vitro from recombinant Rnq1 prion domain (residues 153-405) labeled with Tyr-1-¹³C (14 residues), Leu-1-¹³C (7 residues), or Ala-3-¹³C (13 residues). The carbonyl chemical shifts indicate that most Tyr and Leu residues are in β-sheet conformation. Experiments designed to measure the distance from each labeled residue to the next nearest labeled carbonyl showed that almost all Tyr and Leu carbonyl carbon atoms were ≈0.5 nm from the next nearest Tyr and Leu residues, respectively. This result indicates that the Rnq1 prion domain forms amyloid consisting of parallel β-strands that are either in register or are at most one amino acid out of register. Similar experiments with Ala-3-¹³C indicate that the β-strands are indeed in-register. The parallel in-register structure, now demonstrated for each of the yeast prions, explains the faithful templating of prion strains, and suggests as well a mechanism for the rare hetero-priming that is [PIN⁺]'s defining characteristic.
Proceedings of the National Academy of Sciences of the United States of America © 2008 National Academy of Sciences