<p>In bacteria, FtsZ [<cite idref="PUB00003846"/>, <cite idref="PUB00000910"/>, <cite idref="PUB00007093"/>] is an essential cell division protein which appears to be involved in the initiation of this event. It assembles into a cytokinetic ring on the inner surface of the cytoplasmic membrane at the place where division will occur. The ring serves as a scaffold that is disassembled when septation is completed. FtsZ ring formation is initiated at a singlesite on one side of the bacterium and appears to grow bidirectionally. In <taxon tax_id="562">Escherichia coli</taxon>, MinCD <db_xref db="INTERPRO" dbkey="IPR005526"/>, encoded by the MinB locus, form a complex which appears to block the formation of FtsZ rings at the cell poles, at the ancient mid cell division sites, whilst MinE, encoded at the same locus, specifically prevents the action of MinCD at mid cell.</p><p> FtsZ is a GTP binding protein <db_xref db="PROSITEDOC" dbkey="PDOC00199"/> with a GTPase activity. It undergoes GTP-dependent polymerisation intofilaments (or tubules) that seem to form a cytoskeleton involved in septumsynthesis. The structure and the properties of FtsZ clearly provide it with the capacity for the cytoskeletal, perhaps motor role, necessary for "contraction" along the division plane. In addition, however, the FtsZring structure provides the framework for the recruitment or assembly of the ten or so membrane and cytoplasmic proteins, uniquely required for cell division in E. coli or <taxon tax_id="1423">Bacillus subtilis</taxon>, some of which are required for biogenesis of the new hemispherical poles of the two daughter cells. FtsZ can polymerise into various structures, for example a single linear polymer of FtsZ monomers, called a protofilament. Protofilaments can associate laterally to form pairs (sometimes called thick filaments, bundles (ill-defined linear associations of multiple protofilaments or thick filaments, sheets (parallel or anti-parallel two-dimensional associations of thick filaments and tubes (anti-parallel associations of thick filaments in a circular fashion to form a tubular structure). In addition, small circles of FtsZ monomers (a short protofilament bent around to join itself, apparently head to tail) have been observed and termed mini-rings. </p><p>FtsZ is a protein of about 400 residues which is well conserved across bacterial species and which is also present in the chloroplast of plants [<cite idref="PUB00004215"/>] as well as in archaebacteria [<cite idref="PUB00002291"/>]. FtsZ shows structural similarity with eukaryotic tubulins. This similarity is probably both evolutionary andfunctionally significant.</p> Cell division protein FtsZ, conserved site