ReportElectron Microscopy

2.2 Å resolution cryo-EM structure of β-galactosidase in complex with a cell-permeant inhibitor

Science  07 May 2015:

DOI: 10.1126/science.aab1576

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Abstract

Cryo-electron microscopy (cryo-EM) is rapidly emerging as a powerful tool for protein structure determination at high resolution. Here, we report the structure of a complex between Escherichia coli β-galactosidase and the cell-permeant inhibitor phenylethyl β-d-thiogalactopyranoside (PETG), determined by cryo-EM at a resolution of ~2.2 Å. Besides the PETG ligand, we identified densities in the map for ~800 water molecules and for magnesium and sodium ions. While it is likely that continued advances in detector technology may further enhance resolution, our findings demonstrate that preparation of specimens of adequate quality and intrinsic protein flexibility, rather than imaging or image processing technologies, now represent the major bottlenecks to achieving resolutions close to 2 Å using single particle cryo-EM.

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