Applications of electron cryo-microscopy to cardiovascular research

Electron cryo-microscopy (cryo-EM) techniques have wide applications for the study of biological structures. The focus of this chapter is the use of cryo-EM and associated methods for the analysis of the three-dimensional (3D) structure of proteins and multicomponent macromolecular assemblies. Data evolving from these methods pertaining to the quaternary organization of proteins and protein-protein interactions, bridges an important gap between linear genomic information and understanding physiological function. This chapter provides general methods for examining two-dimensional crystalline arrays of proteins as well as single, randomly orientated protein complexes. It is significant that single-particle analysis of electron microscopy images has provided the only 3D data to-date for the two principal components of muscle excitation contraction coupling in the heart, namely the L-type voltage-gated calcium channel and the ryanodine receptor. This chapter describes approaches for identifying the extracellular and intracellular domains of the 3D structure of the L-type voltage-gated calcium channel and also incorporates general details for labeling and visualizing His-tagged proteins.