Structural Snapshots of Actively Translating Human Ribosomes
Graphical Abstract Highlights d Structural analysis of actively translating ribosomes d Identification of significantly populated states at close to in vivo conditions d Functional states feature localized chemical and conformational heterogeneity d Human 80S ribosome map at near-atomic resolution reveals native interactions In Brief Multiparticle cryo-EM analysis reveals 11 distinct functional states from a native actively translating human polysomal sample, providing insights into the
... ation of the human ribosome at near-atomic resolution and highlighting the functional importance of both rigid and flexible regions. Accession Numbers 5AJ0 Behrmann et al., 2015, Cell 161, 845-857 May 7, 2015 ª2015 Elsevier Inc. http://dx. SUMMARY Macromolecular machines, such as the ribosome, undergo large-scale conformational changes during their functional cycles. Although their mode of action is often compared to that of mechanical machines, a crucial difference is that, at the molecular dimension, thermodynamic effects dominate functional cycles, with proteins fluctuating stochastically between functional states defined by energetic minima on an energy landscape. Here, we have used cryo-electron microscopy to image ex-vivo-derived human polysomes as a source of actively translating ribosomes. Multiparticle refinement and 3D variability analysis allowed us to visualize a variety of native translation intermediates. Significantly populated states include not only elongation cycle intermediates in pre-and post-translocational states, but also eEF1A-containing decoding and termination/recycling complexes. Focusing on the post-translocational state, we extended this assessment to the single-residue level, uncovering striking details of ribosome-ligand interactions and identifying both static and functionally important dynamic elements.