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Structural dependence of HET-s amyloid fibril infectivity assessed by cryoelectron microscopy.

ABSTRACT: HET-s is a prion protein of the fungus Podospora anserina which, in the prion state, is active in a self/nonself recognition process called heterokaryon incompatibility. Its prionogenic properties reside in the C-terminal "prion domain." The HET-s prion domain polymerizes in vitro into amyloid fibrils whose properties depend on the pH of assembly; above pH 3, infectious singlet fibrils are produced, and below pH 3, noninfectious triplet fibrils. To investigate the correlation between structure and infectivity, we performed cryo-EM analyses. Singlet fibrils have a helical pitch of approximately 410 ? and a left-handed twist. Triplet fibrils have three protofibrils whose lateral dimensions (36 × 25 ?) and axial packing (one subunit per 9.4 ?) match those of singlets but differ in their supercoiling. At 8.5-? resolution, the cross-section of the singlet fibril reconstruction is largely consistent with that of a ?-solenoid model previously determined by solid-state NMR. Reconstructions of the triplet fibrils show three protofibrils coiling around a common axis and packed less tightly at pH 3 than at pH 2, eventually peeling off. Taken together with the earlier observation that fragmentation of triplet fibrils by sonication does not increase infectivity, these observations suggest a novel mechanism for self-propagation, whereby daughter fibrils nucleate on the lateral surface of singlet fibrils. In triplets, this surface is occluded, blocking nucleation and thereby explaining their lack of infectivity.

SUBMITTER: Mizuno N

PROVIDER: S-EPMC3044374 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature

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Structural dependence of HET-s amyloid fibril infectivity assessed by cryoelectron microscopy.

Mizuno Naoko N Baxa Ulrich U Steven Alasdair C AC

Proceedings of the National Academy of Sciences of the United States of America 20110207 8

HET-s is a prion protein of the fungus Podospora anserina which, in the prion state, is active in a self/nonself recognition process called heterokaryon incompatibility. Its prionogenic properties reside in the C-terminal "prion domain." The HET-s prion domain polymerizes in vitro into amyloid fibrils whose properties depend on the pH of assembly; above pH 3, infectious singlet fibrils are produced, and below pH 3, noninfectious triplet fibrils. To investigate the correlation between structure a ...[more]

PMID: 21300906

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Structural dependence of HET-s amyloid fibril infectivity assessed by cryoelectron microscopy.

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Structural dependence of HET-s amyloid fibril infectivity assessed by cryoelectron microscopy.

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