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Cryo-Electron Microscopy Structure of Human Peroxiredoxin-3 Filament Reveals the Assembly of a Putative Chaperone

Mazdak Radjainia, Hariprasad Venugopal, Ambroise Desfosses, Amy J. Phillips, N. Amy Yewdall, Mark B. Hampton, Juliet A. Gerrard, and Alok K. Mitra

Structure- 2015- 23(5):: 912-920

Peroxiredoxins (Prxs) are a ubiquitous class of thiol-dependent peroxidases that play an important role in the protection and response of cells to oxidative stress. The catalytic unit of typical 2-Cys Prxs are homodimers, which can self-associate to form complex assemblies that are hypothesized to have signaling and chaperone activity. Mitochondrial Prx3 forms dodecameric toroids, which can further stack to form filaments, the so-called high-molecular-weight (HMW) form that has putative holdase activity. We used single-particle analysis and helical processing of electron cryomicroscopy images of human Prx3 filaments induced by low pH to generate a ∼7-Å resolution 3D structure of the HMW form, the first such structure for a 2-Cys Prx. The pseudo-atomic model reveals interactions that promote the stacking of the toroids and shows that unlike previously reported data, the structure can accommodate a partially folded C terminus. The HMW filament lumen displays hydrophobic patches, which we hypothesize bestow holdase activity.

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