1 June 2017
CARD, caspase activation and recruitment domain, EM, electron microscopy, FSC, Fourier shell correlation, IHRSR, iterative helical real-space reconstruction, MAVS, mitochondrial antiviral signaling protein, TMV, tobacco mosaic virus, Helical symmetry, Single-particle analysis, Cryo-electron microscopy, Image processing, Regularised likelihood optimisation
We describe a new implementation for the reconstruction of helical assemblies in the empirical Bayesian framework of RELION. Our approach calculates optimal linear filters for the 3D reconstruction by embedding helical symmetry operators in Fourier-space, and deals with deviations from perfect helical symmetry through Gaussian-shaped priors on the orientations of individual segments. By incorporating our approach into the standard pipeline for single-particle analysis in RELION, our implementation aims to be easily accessible for non-experienced users. Although our implementation does not solve the problem that grossly incorrect structures can be obtained when the wrong helical symmetry is imposed, we show for four different test cases that it is capable of reconstructing structures to near-atomic resolution.