DOI: 10.1101/488403Dec 6, 2018Paper

Retrieving High-Resolution Information from Disordered 2D Crystals by Single Particle Cryo-EM

BioRxiv : the Preprint Server for Biology
Ricardo D RighettoHenning Stahlberg

Abstract

Electron crystallography can reveal the structure of membrane proteins within 2D crystals under close-to-native conditions. High-resolution structural information can only be reached if crystals are perfectly flat and highly ordered. In practice, such crystals are difficult to obtain. Available image unbending algorithms correct for disorder, but only perform well on images of non-tilted, flat crystals, while out-of-plane distortions are not addressed. Here, we present an approach that employs single-particle refinement procedures to locally unbend crystals in 3D. With this method, density maps of the MloK1 potassium channel with a resolution of 4 Angstroms were obtained from images of 2D crystals that do not diffract beyond 10 Angstroms. Furthermore, 3D classification allowed multiple structures to be resolved, revealing a series of MloK1 conformations within a single 2D crystal. This conformational heterogeneity explains the poor diffraction observed and is related to channel function. The approach is implemented in the FOCUS package.

Related Concepts

Classification
Ion Channel
Membrane Proteins
Electron Microscopy
Potassium Channel
Crystal Structure
Three-dimensional
Electron Crystallography
Structure
Procedure With a Procedure Focus

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