Comparing Cryo-EM Reconstructions and Validating Atomic Model Fit Using Difference Maps

Agnel Praveen Joseph, Ingvar Lagerstedt, Arjen Jakobi, Tom Burnley, Ardan Patwardhan, Maya Topf, Martyn Winn

Research output: Contribution to journalArticleScientificpeer-review

4 Citations (Scopus)
11 Downloads (Pure)

Abstract

Cryogenic electron microscopy (cryo-EM) is a powerful technique for determining structures of multiple conformational or compositional states of macromolecular assemblies involved in cellular processes. Recent technological developments have led to a leap in the resolution of many cryo-EM data sets, making atomic model building more common for data interpretation. We present a method for calculating differences between two cryo-EM maps or a map and a fitted atomic model. The proposed approach works by scaling the maps using amplitude matching in resolution shells. To account for variability in local resolution of cryo-EM data, we include a procedure for local amplitude scaling that enables appropriate scaling of local map contrast. The approach is implemented as a user-friendly tool in the CCP-EM software package. To obtain clean and interpretable differences, we propose a protocol involving steps to process the input maps and output differences. We demonstrate the utility of the method for identifying conformational and compositional differences including ligands. We also highlight the use of difference maps for evaluating atomic model fit in cryo-EM maps.

Original languageEnglish
Pages (from-to)2552-2560
JournalJournal of Chemical Information and Modeling
Volume60
Issue number5
DOIs
Publication statusPublished - 2020

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