Solution structure of ZipA, a crucial component of Escherichia coli cell division

ZipA, an essential component of cell division in Escherichia coli, interact s with the FtsZ protein at the midcell in one of the initial steps of septu m formation, The high-resolution solution structure of the 144-residue C-te rminal domain of E. coli ZipA (ZiPA(185-328)) has been determined by multid imensional heteronuclear NMR. A total of 30 structures were calculated by m eans of hybrid distance geometry-simulated annealing using a total of 2758 experimental NMR restraints. The atomic root means square distribution abou t the mean coordinate positions for residues 6-142 for the 30 structures is 0.37 +/- 0.04 Angstrom for the backbone atoms, 0.78 +/- 0.05 Angstrom for all atoms, and 0.45 +/- 0.04 Angstrom, for all atoms excluding disordered s ide chains. The NMR solution structure of ZiPA(185-328) is composed of thre e alpha-helices and a beta-sheet consisting of six antiparallel beta-strand s where the alpha-helices and the beta-sheet form surfaces directly opposit e each other. A C-tenninal peptide from FtsZ has been shown to bind ZiPA(18 5-328) in a hydrophobic channel formed by the beta-sheet providing insight into the ZipA-FtsZ interaction. An unexpected similarity between the ZiPA(1 85-328) fold and the split beta-alpha-beta fold observed in many RNA bindin g proteins may further our understanding of the critical ZipA-FtsZ interact ion.