title: 2.2 Å resolution cryo-EM structure of β-galactosidase in complex with a cell-permeant inhibitor.
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 an average resolution of ~2.2 angstroms (Å). Besides the PETG ligand, we identified densities in the map for ~800 water molecules and for magnesium and sodium ions. Although 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 routinely achieving resolutions close to 2 Å using single-particle cryo-EM.
authors.affiliation: Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Alberto
authors.initials: A
authors.lastname: Bartesaghi
authors.affiliation: Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Alan
authors.initials: A
authors.lastname: Merk
authors.affiliation: Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Soojay
authors.initials: S
authors.lastname: Banerjee
authors.affiliation: Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Doreen
authors.initials: D
authors.lastname: Matthies
authors.affiliation: Laboratory of Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Xiongwu
authors.initials: X
authors.lastname: Wu
authors.affiliation: Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Jacqueline L S
authors.initials: JL
authors.lastname: Milne
authors.affiliation: Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA. ss1@nih.gov.
authors.forename: Sriram
authors.initials: S
authors.lastname: Subramaniam
mesh_terms: D020134:Catalytic Domain; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry*; D013862:Thiogalactosides / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D001616:beta-Galactosidase / Q000737:chemistry*
chemical_list: D029968:Escherichia coli Proteins; D013862:Thiogalactosides; D014867:Water; C066907:phenylethylthio-beta-galactopyranoside; D001616:beta-Galactosidase