Electron Microscopy Alone Reveals Protein Machine’s Structure

The first near-atomic-level glimpse of a massive 3-megadalton biological machine was obtained this year using only cryogenic electron microscopy (cryoEM), without the need for protein crystallization or extensive purification protocols. The analytical milestone was achieved on the yeast mitochondrial ribosome’s large subunit, a 39-protein complex crucial for making mitochondrial membrane proteins in the energy-producing organelle in yeast cells. The 3.2-A structure was determined by Venkatraman Ramakrishnan, Sjors H. W. Scheres, and their colleagues at the MRC Laboratory of Molecular Biology, in Cambridge, England (Science 2014, DOI: 10.1126/science.1249410). “This paper is one of the most exciting results in structural biology in recent years,” commented Nenad Ban, a structural biologist at the Swiss Federal Institute of Technology (ETH), Zurich. It’s a methodological breakthrough to be able to use electron microscopy to structurally analyze such a large protein complex at atomic-level resolution, Ban ex...