Abstract
MinD is a widely conserved ATPase that has been demonstrated to play a pivotal role in selection of the division site in eubacteria and chloroplasts. It is a member of the large ParA superfamily of ATPases that are characterized by a deviant Walker-type ATP-binding motif. MinD localizes to the cytoplasmic face of the inner membrane in Escherichia coli, and its association with the inner membrane is a prerequisite for membrane recruitment of the septation inhibitor MinC. However, the mechanism by which MinD associates with the membrane has proved enigmatic; it seems to lack a transmembrane domain and the amino acid sequence is devoid of hydrophobic tracts that might predispose the protein to interaction with lipids. In this study, we show that the extreme C-terminal region of MinD contains a highly conserved 8- to 12-residue sequence motif that is essential for membrane localization of the protein. We provide evidence that this motif forms an amphipathic helix that most likely mediates a direct interaction between MinD and membrane phospholipids. A model is proposed whereby the membrane-targeting motif mediates the rapid cycles of membrane attachment-release-reattachment that are presumed to occur during pole-to-pole oscillation of MinD in E. coli.