E. coli Cell Division (ZipA)
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Average ZipA Structure PDBID: 1F7W Biochemistry (2000), 39(31), 9146-9156. |
| NMR ZipA:FtsZ Peptide Complex Structure
Structure published in: Biochemistry (2000), 39(31), 9146-9156. X-ray structures: PDBID: 1F46, 1F47 EMBO J. (2000), 19:3179. ZipA is shown as a protein cartoon and the FtsZ peptide is shown as licorice bonds. |
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| Model of the proposed FtsZ-ZipA complex [Cell (1997)88 175-185] | Over expression or deletion of ZipA results in filamentation [Cell (1997)88 175-185] |
ZipA is essential for cell division and viability in E. coli. Experiments with the green fluorescent protein fusion of ZipA have demonstrated that only prior localization of FtsZ is required for localization of ZipA to midcell. Changes in the relative abundance of ZipA in the cell, either by depletion or over-expression, result in filamentation. The morphology of these filaments resembles those observed for cells in which FtsZ has been depleted. This is consistent with the observation that both ZipA and FtsZ are involved at the very early stage of cell division.
ZipA is a 328 amino acid protein that is composed of 5 regions or domains. The N-terminus is a highly hydrophobic region of approximately 25 amino acids which forms the transmembrane domain that anchors the protein to the cytoplasmic membrane. This is followed by a basic region (~ 23 a.a.), an acidic region (~17 a.a.), and a long proline rich region. The C-terminal domain (residues 189-328) has been shown to be sufficient for binding to FtsZ and has several areas that are conserved among the seven ZipA sequences identified to date. Since ZipA is anchored to the cytoplasmic membrane while binding FtsZ, it has been speculated that the function of ZipA may be to link the membrane with the FtsZ rings, to stabilize or organize the FtsZ rings, or to link invagination of the membrane to constriction of the FtsZ ring during septation. Since changes in the relative abundance of ZipA in the cell result in filamentation, disruption of the ZipA-FtsZ interaction would likely disrupt cell division and cause cell lysis, suggesting that the ZipA-FtsZ interaction may be a viable therapeutic target for drug development.
The NMR solution structure of ZipA185-328 is comprised of three a-helices and a b-sheet consisting of six anti-parallel b-strands where the a-helices and the b-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 b-sheet providing insight into the ZipA-FtsZ interaction. An unexpected similarity between the ZipA185-328 fold and the split b-a-b fold observed in many RNA binding proteins may further our understanding of the critical ZipA-FtsZ interaction.