Assembly properties of FtsZ from cyanobacterium Synechocystis sp. PCC 6803

Tubulin homologue FtsZ is the major cytoskeletal protein in the bacterial cell division machinery. Here, we studied the biochemical and assembly properties of SyFtsZ, FtsZ from cyanobacterium Synechocystis sp. PCC 6803. SyFtsZ had a slow GTPase activity of around 0.4 GTP per FtsZ per minute and assembled into thick, straight protofilament bundles and curved bundles designated toroids. The assembly of SyFtsZ in the presence of GTP occurred in two stages. The first stage was assembled into single straight protofilaments and opened circles; the second stage was association of the protofilaments into straight protofilament bundles and toroids. In addition to these assemblies in GTP, highly curved oligomers and minirings could be observed after GTP hydrolysis or in the presence of GDP. Those three types of protofilaments of SyFtsZ provide support for the hypothesis for a constriction force based on curved protofilaments.