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Arch Biochem Biophys. 2015 Sep 1;581:68-77. doi: 10.1016/j.abb.2015.06.006. Epub 2015 Jun 17.

3D reconstruction of two-dimensional crystals.

Author information

1
Center for Cellular Imaging and NanoAnalytics, Biozentrum, University of Basel, Mattenstrasse 26, 4058 Basel, Switzerland.
2
Department of BioNanoscience, Delft University of Technology, Van der Waalsweg 8, 2628 CH Delft, The Netherlands; Department of Pharmacology, Case Western Reserve University, 10900 Euclid Avenue, Wood Bldg 321D, Cleveland, OH 44106-4965, USA. Electronic address: a.h.engel@tudelft.nl.

Abstract

Electron crystallography of two-dimensional (2D) crystals determines the structure of membrane proteins in the lipid bilayer by imaging with cryo-electron microscopy and image processing. Membrane proteins can be packed in regular 2D arrays by their reconstitution in the presence of lipids at low lipid to protein weight-to-weight ratio. The crystal quality depends on the protein purity and homogeneity, its stability, and on the crystallization conditions. A 2D crystal presents the membrane protein in a functional and fully lipidated state. Electron crystallography determines the 3D structure even of small membrane proteins up to atomic resolution, but 3D density maps have a better resolution in the membrane plane than in the vertical direction. This problem can be partly eliminated by applying an iterative algorithm that exploits additional known constraints about the 2D crystal. 2D electron crystallography is particularly attractive for the structural analysis of membrane proteins that are too small for single particle analyses and too unstable to form 3D crystals. With the recent introduction of direct electron detector cameras, the routine determination of the atomic 3D structure of membrane-embedded membrane proteins is in reach.

KEYWORDS:

2D crystallization; 3D reconstruction; Electron crystallography; Lipid; Membrane protein; Missing cone

PMID:
26093179
DOI:
10.1016/j.abb.2015.06.006
[Indexed for MEDLINE]

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