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Figure 1
Cryo-EM density map of β-galactosidase at 1.8 Å resolution. (a). Surface representation of the β-galactosidase tetramer. (b)–(d) Visualization of selected map regions showing delineation of secondary-structural elements and amino-acid densities. To provide a direct comparison with our earlier work, the regions shown here are identical to selected panels of Figs. 1 and 2 from our previous work (Bartesaghi et al., 2018BB1), where we reported a 2.2 Å map of β-galactosidase using data collected on a Titan Krios electron microscope operated at 300 kV. The segments display `holes' in residues such as (b) the pyrrolidine ring in Pro451 and the indole group of Trp456, and (c) in Phe627 with the side-chain densities delineated more clearly than in the earlier 2.2 Å map. The region of the protein highlighted in panel (d) shows three additional water molecules to that reported in the corresponding panel in the 2.2 Å map [Fig. 2(a) in our previous work (Bartesaghi et al., 2018BB1)].

Volume 7| Part 4| July 2020| Pages 639-643
ISSN: 2052-2525