Abstract
Using single-particle electron cryo-microscopy (cryo-EM), it is possible to obtain multiple reconstructions showing the 3D structures of proteins imaged as a mixture. Here, it is shown that automatic map interpretation based on such reconstructions can be used to create atomic models of proteins as well as to match the proteins to the correct sequences and thereby to identify them. This procedure was tested using two proteins previously identified from a mixture at resolutions of 3.2 Å, as well as using 91 deposited maps with resolutions between 2 and 4.5 Å. The approach is found to be highly effective for maps obtained at resolutions of 3.5 Å and better, and to have some utility at resolutions as low as 4 Å.
Highlights
One of the major advantages of single-particle electron cryomicroscopy as a structural biology tool is that it can be used to determine the individual structures of macromolecules present in a mixture (Verbeke et al, 2020; Ho et al, 2020)
The methods described here are incorporated into the CryoID application for protein identification by cryo-EM described in Ho et al (2020)
Application of automated protein identification to previously analyzed cryo-EM maps obtained from an enriched cellular lysate
Summary
One of the major advantages of single-particle electron cryomicroscopy (cryo-EM) as a structural biology tool is that it can be used to determine the individual structures of macromolecules present in a mixture (Verbeke et al, 2020; Ho et al, 2020) This capability comes from the classification process, in which each particle is assigned to a class (a view of a particular molecule), classes that share 3D information are grouped, and each group of classes is analyzed to yield an individual structure (Scheres, 2012; Sigworth, 1998; Nogales, 2016). The methods described here are incorporated into the CryoID application for protein identification by cryo-EM described in Ho et al (2020)
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