Single Particle CryoEM of Integral Membrane Proteins

Abstract

The Keck Advanced Microscopy Laboratory, Department of Biochemistry and Biophysics University of California, 600 16th Street, San Francisco, CA 94158As a versatile tool in structural biology, single particle electron cryo-microscopy (cryo-EM) has achieved milestones of determining near atomic resolution three-dimensional (3D) reconstructions of non-enveloped viruses with icosahedral symmetry. Recent technological breakthroughs in single particle cryo-EM, particularly the development of novel dose-fractionated image acquisition method based on CMOS direct electron detection camera and robust algorithms for correction of motion induced image blurring, are transformative. It has enabled near atomic resolution structure determinations of a broad range of proteins complexes without the need of crystals.One of the major challenges in structural biology is to determine structures of integral membrane proteins at different functional states. The bottleneck for X-ray crystallography is to trap and crystallize the same membrane protein in different conformations. Without constrain of crystallization, it is now possible to determine structures of integral membrane proteins at subnanometer to near atomic resolutions. At this resolution range, it is possible to derive the structural information from docking of known or homology model into subnanometer resolution cryo-EM density maps, or to build de novo atomic structure directly from the 3D density map. We will discuss some of the recent technological advancements specific for structural analysis of integral membrane proteins.