title: Identifying conformational states of macromolecules by eigen-analysis of resampled cryo-EM images.
abstract: We present the codimensional principal component analysis (PCA), a novel and straightforward method for resolving sample heterogeneity within a set of cryo-EM 2D projection images of macromolecular assemblies. The method employs PCA of resampled 3D structures computed using subsets of 2D data obtained with a novel hypergeometric sampling scheme. PCA provides us with a small subset of dominating "eigenvolumes" of the system, whose reprojections are compared with experimental projection data to yield their factorial coordinates constructed in a common framework of the 3D space of the macromolecule. Codimensional PCA is unique in the dramatic reduction of dimensionality of the problem, which facilitates rapid determination of both the plausible number of conformers in the sample and their 3D structures. We applied the codimensional PCA to a complex data set of Thermus thermophilus 70S ribosome, and we identified four major conformational states and visualized high mobility of the stalk base region.
authors.affiliation: Department of Biochemistry and Molecular Biology, Houston Medical School, The University of Texas, Houston, TX 77030, USA. pawel.a.penczek@uth.tmc.edu
authors.forename: Pawel A
authors.initials: PA
authors.lastname: Penczek
authors.forename: Marek
authors.initials: M
authors.lastname: Kimmel
authors.forename: Christian M T
authors.initials: CM
authors.lastname: Spahn
mesh_terms: D000465:Algorithms; D000704:Analysis of Variance; D001426:Bacterial Proteins / Q000737:chemistry; D020285:Cryoelectron Microscopy / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008958:Models, Molecular; D010444:Peptide Elongation Factor Tu / Q000737:chemistry; D025341:Principal Component Analysis; D054730:Protein Interaction Domains and Motifs; D020836:Protein Structure, Quaternary; D012343:RNA, Transfer / Q000737:chemistry; D054658:Ribosome Subunits, Large / Q000737:chemistry; D016963:Thermus thermophilus
chemical_list: D001426:Bacterial Proteins; D012343:RNA, Transfer; D010444:Peptide Elongation Factor Tu
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