High resolution cryogenic transmission electron microscopy study of Escherichia coli Dps protein: First direct observation in quasinative state

Abstract The Dps protein of Escherichia coli is a homododecamer with an internal cavity accumulating iron oxides, transformed from ambient toxic Fe 2+ into a harmless inorganic core. High resolution cryogenic transmission electron microscopy was applied to visualize the protein molecules and to characterize their ability to self-organization. Due to ultrafast freezing, the Dps dodecameric particles were observed as a “snapshot” of their natural state, and highly ordered two-dimensional layers with hexagonal symmetry were obtained. Thus, it became clear, that “super structured monolayers”, spanning over several thousand square nanometers can be formed under certain cryogenic regimes.