Assembly of three FtsZ mutants. (a) FtsZ84 assembled with GTP and 0.6 mg/ml DEAE dextran formed protofilament sheets of exceptional size and regularity (although the quality of the sheets varied for different preparations). Note that wild type FtsZ would have formed exclusively tubes under these conditions. (b) D86K assembled into tubes in MEMK6.5. No DEAE dextran and no GTP or GDP were added. (c) D86K at 0.5 mg/ml in MEMK6.5 plus 2 mM GTP (no DEAE dextran) formed twin protofilaments and short tubes. (d,e) D209A plus 0.6 mg/ml DEAE dextran and 10 mM GTP formed long spirals of protofilament bundles, and some circular hoops. (f) D209A in 2 mM GMPCPP also formed hoops, and these are mixed with tubes typical of assembly in GDP.