Future Directions of Electron Crystallography
In biological science, there are still many interesting and fundamental yet difficult questions, such as those in neuroscience, remaining to be answered. Structural and functional studies of membrane proteins, which are key molecules of signal transduction in neural and other cells, are essential for understanding the molecular mechanisms of many fundamental biological processes. Technological and instrumental advancements of electron microscopy have facilitated comprehension of structural studies of biological components, such as membrane proteins. While X-ray crystallography has been the main method of structure analysis of proteins including membrane proteins, electron crystallography is now an established technique to analyze structures of membrane proteins in the lipid bilayer, which is close to their natural biological environment. By utilizing cryo-electron microscopes with helium-cooled specimen stages, structures of membrane proteins were analyzed at a resolution better than 3 Å. Such high-resolution structural analysis of membrane proteins by electron crystallography opens up the new research field of structural physiology. Considering the fact that the structures of integral membrane proteins in their native membrane environment without artifacts from crystal contacts are critical in understanding their physiological functions, electron crystallography will continue to be an important technology for structural analysis. In this chapter, I will present several examples to highlight important advantages and to suggest future directions of this technique.
Key wordsStructural physiology Native membrane environment Physiologically relevant structural information Charge status analysis 2D crystal contacts Physiological lipid and ionic setting Helium-cooled specimen stage Experimental phase data
These studies were performed in nice collaboration with many researchers whose names were recorded as authors in each referenced paper and I appreciate the contribution by each researcher. This work was supported by Grants-in-Aid for Scientific Research (S) and the Japan New Energy and Industrial Technology Development Organization (NEDO).