A complete catalog of wild-type Sup35 prion variants and their protein-only propagation
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Twenty-three prion variants of the wild-type Sup35 protein are obtained, including 19 novel ones and 4 previously documented, namely, VH, VK, VL, and W8. Their uniqueness and non-composite nature are demonstrated. Specific infectivity is generated de novo for most variants by adding prion particles to solutions of a purified Sup35 N-terminal fragment, thereby supporting the protein-only composition. Sup35 prions isolated by other laboratories are identified within the collection and found to fall into a narrow set of five variant types that are readily inducible in vivo by Sup35 overexpression. The work establishes an unambiguous and extensive collection of prion variants, demonstrating that a protein, by itself, in the absence of genetic and conformational co-factors, could adopt a great number of structures. In light of recent high-resolution structures of other amyloids, we discuss how the diverse folding is achieved in spite of apparent contradiction to the classical paradigm that a protein’s structure is uniquely determined by its sequence.
Keywords[PSI+] Prion Variants Amyloid Saccharomyces cerevisiae
We thank Drs. S. W. Liebman, M. Tanaka, and R. B. Wickner for yeast strains; Drs. V. V. Kushnirov, M. Tanaka, and R. B. Wickner for discussion; S.-P.Lee, S.-P. Tsai, and W.-L. Pong for help with imaging; T. T. Le, Y. Chen, H.-C. Lee, and C.-I. Yu for technical assistance. This work was supported by Grant 105-2311-B-001-056 from Ministry of Science and Technology, Taiwan, Republic of China.
Both authors designed the study, performed experiments, and wrote the manuscript.
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