Abstract
Mitochondrial antiviral signaling (MAVS) protein forms prion-like aggregates mediated by the N-terminal caspase activation and recruitment domain (CARD) and activates antiviral signaling cascades. Purified MAVS CARD from culture cells self-assembles into filaments. Previously, we reported a low-resolution cryoEM structure of MAVS CARD filament, which exhibits a C3 symmetry with a rotation of −53.6° and an axial rise of 16.8 A for every unit in the filament (Xu et al., 2014). Recently, a cryoEM reconstruction of MAVS CARD filaments at 3.6 A resolution was reported with a C1 helical symmetry of a rotation of −101.1° and an axial rise of 5.1 A per subunit (Wu et al., 2014). The differences in these two models were carefully analyzed recently (Egelman, 2014), which suggested that the helical ambiguity in helical reconstruction was not fully resolved in our previous analysis (Xu et al., 2014). We recently collected a new dataset at higher resolutions. Using a newly developed method for analysis of helical filaments (Clemens et al., 2015), we obtained a 4.2 A resolution reconstruction of MAVS CARD filaments purified from mammalian cells under native conditions. The new model shows that the MAVS CARD filament exhibits a C1 helical symmetry in agreement with Wu et al. (2014).
Highlights
Mitochondrial antiviral signaling (MAVS) protein forms prion-like aggregates mediated by theN-terminal caspase activation and recruitment domain (CARD) and activates antiviral signaling cascades.Purified MAVS CARD from culture cells self-assembles into filaments
A cryoEM reconstruction of MAVS CARD filaments at 3.6 Aresolution was reported with a C1 helical symmetry of a rotation of −101.1 ̊ and an axial rise of 5.1 Aper subunit (Wu et al, 2014)
CryoEM images of Flag-tagged MAVS CARD protein, which was expressed in HEK293T cells and purified as described previously (Xu et al, 2014), were collected using automated data acquisition in a Titan Krios with a Falcon II direct electron detector (Figure 1A; see ‘Materials and methods’ section for detail)
Summary
Mitochondrial antiviral signaling (MAVS) protein forms prion-like aggregates mediated by theN-terminal caspase activation and recruitment domain (CARD) and activates antiviral signaling cascades.Purified MAVS CARD from culture cells self-assembles into filaments. We reported a lowresolution cryoEM structure of MAVS CARD filament, which exhibits a C3 symmetry with a rotation of −53.6 ̊ and an axial rise of 16.8 Afor every unit in the filament (Xu et al, 2014). A cryoEM reconstruction of MAVS CARD filaments at 3.6 Aresolution was reported with a C1 helical symmetry of a rotation of −101.1 ̊ and an axial rise of 5.1 Aper subunit (Wu et al, 2014). The differences in these two models were carefully analyzed recently (Egelman, 2014), which suggested that the helical ambiguity in helical reconstruction was not fully resolved in our previous analysis (Xu et al, 2014). The new model shows that the MAVS CARD filament exhibits a C1 helical symmetry in agreement with Wu et al (2014)
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