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 (ZipA185-328) 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 ZipA185-328 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 ZipA185-328 in a hydrophobic channel formed by the β-sheet providing insight into the ZipA-FtsZ interaction. An unexpected similarity between the ZipA185-328 fold and the split β-α-β fold observed in many RNA binding proteins may further our understanding of the critical ZipA-FtsZ interaction.
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