Cells constitute the smallest autonomous units of life. Supramolecular complexes carry out essentially all functions and processes and form the cells structural elements. The tightly regulated structural and functional organization of a cell at this level is currently only rudimentary understood. A comprehensive analysis of this organization and its dynamic changes requires tools that allow for studying these complexes in their native environment. We apply electron cryo tomography (cryo-ET) in combination with other techniques to approach selected aspects of this highly ordered network analyzing protein complexes in situ. Sample preparation by fast vitrification, i.e. embedding in amorphous ice, ensures excellent preservation of structure down to the atomic level.
We have pioneered the application of cryo-ET to isolated pleomorphic viruses revealing their three-dimensional supramolecular organization. Examples are virions of Herpes simplex virus, HIV-1 and Uukuniemivirus. More recently we have moved towards cell biology of virus infection. Understanding the entirety of a virus’ ‘life cycle’ requires an understanding of its transient structures at the molecular level. The aim is a comprehensive picture of the functional interaction between viral protein complexes and cellular structures in the course of the infection. Viruses also serve as dedicated tools to mine the molecular detail of cellular tomograms. Being able to enter cells via physiological pathways and being recognizable among the multitude of other structural features inside the hosts cytoplasm viruses allow following dynamic cellular processes.
Cryo electron microscopy provides an excellent platform for interactions with other approaches, like biochemical and X-ray crystallographic studies and integration of these results with native sub-cellular structural information. We are involved in various efforts of methods development including the combination of cryo electron tomographic imaging with ‘single particle’ approaches, fluorescence microscopy and X-ray microscopy/tomography in a correlative fashion, proteomics and frozen hydrated sectioning.