Practice question

Because FtsZ polymers lack lipid binding domains they require membrane tethering proteins to assemble productive contractile structure. In Escherichia coli two proteins provide anchoring: FtsA and ZipA. FtsA is actin homolog belonging to actin Hsp70 superfamily containing ATP binding site and C terminal amphipathic helix inserting into inner membrane, interacting with conserved C terminal peptide DPAFLRK of FtsZ via pocket. FtsA also forms minirings on membrane recruiting downstream divisome FtsN. ZipA is bitopic membrane protein with N terminal transmembrane anchor and periplasmic domain containing FtsZ binding region, stabilizing bundling though not essential at low temperature. FtsZ tethered can exert inward force as filaments bend upon GTP hydrolysis pulling membrane via anchored ends. FtsK is DNA translocase not anchor, FtsN late recruitment activation factor. Depletion FtsA leads to spirals delocalized Z, division block filamentous phenotype. Understanding anchoring illustrates how prokaryotic cytoskeleton generates force without myosin, via polymerization coupled membrane attachment informing design of synthetic divisomes in artificial cells.