Structure Determination of Fe(II) Transporters by Electron Crystallography

Ions of transition metals such as Fe, Cu, and Zn play an important role in a large number of biochemical processes such as catalytic conversions, electron transport and the stabilization of certain protein folds. Despite their importance, little is known about the acquisition and homeostasis of metal ions. Over the past few years, a growing number of metal ion transporters have been identified by genetic approaches. A specific example is the bacterial Fe(II) transporter FeoB which mediates the uptake of iron in E. coli. The N-terminus of FeoB shows limited similarity to ATP/GTP - binding proteins and at least eight hydrophobic segments are predicted to span the membrane. When over-expressed, FeoB becomes the major protein component of the plasma membrane thus providing sufficient amounts of protein for structural studies. The goal of this project is to grow two-dimensional crystals of FeoB, to analyse these crystals by high resolution electron cryo-microscopy and image analysis, and to characterize a possible energy dependent Fe(II) transport. This study will provide new insights into the mechanisms of iron transport across cellular membranes. Furthermore, the results will contribute to a better understanding of the molecular basis of diseases that are caused by abnormal trafficking of transition metal ions.