Solution Structure of ZipA, a Crucial Component ofEscherichia coliCell Division

Abstract

ZipA, an essential component of cell division in Escherichia coli, interacts with the FtsZ protein at the midcell in one of the initial steps of septum formation. The high-resolution solution structure of the 144-residue C-terminal domain of E. coli ZipA (ZipA_185-328) has been determined by multidimensional heteronuclear NMR. A total of 30 structures were calculated by means of hybrid distance geometry-simulated annealing using a total of 2758 experimental NMR restraints. The atomic root means square distribution about the mean coordinate positions for residues 6−142 for the 30 structures is 0.37 ± 0.04 Å for the backbone atoms, 0.78 ± 0.05 Å for all atoms, and 0.45 ± 0.04 Å for all atoms excluding disordered side chains. The NMR solution structure of ZipA_185-328 is composed of three α-helices and a β-sheet consisting of six antiparallel β-strands where the α-helices and the β-sheet form surfaces directly opposite each other. A C-terminal peptide from FtsZ has been shown to bind ZipA_185-328 in a hydrophobic channel formed by the β-sheet providing insight into the ZipA−FtsZ interaction. An unexpected similarity between the ZipA_185-328 fold and the split β−α−β fold observed in many RNA binding proteins may further our understanding of the critical ZipA−FtsZ interaction.