Involves nucleotide binding and hydrolysis, but how this occurs is not well understood. Septins polymerize by interacting with one another via the N- and C-termini and the nucleotide-binding pocket of their GTP binding domains. Structural studies indicate that GTP-binding triggers conformational changes that destabilize the NC interface, while GTP hydrolysis appears to have the opposite effect on the G interface, which is more stable in its GDP- than GTP-bound state. Septin monomers hydrolyze GTP faster than septin dimers and oligomers, whose nucleotide-binding pocket is not readily accessible by GTP. Not all septins, however, are capable of hydrolyzing GTP. Septins that lack a threonine residue, which is critical for GTP hydrolysis, are constitutively bound to GTP and septin hetero-hexamers contain both GDP and GTP at a ratio of 2:1. Interestingly, in vitro biochemical studies of septin assembly have shown that GTP-gamma-S, a slowly hydrolysable GTP analog, promotes the assembly of septin monomers into homo-polymeric filaments. While more work is needed to fully understand how GTP-binding and hydrolysis affects the dynamics of septin filament assembly, pharmacological agents that stabilize or depolymerize septin filaments can be useful tools in understanding the mechanisms of septin assembly and function. To date, forchlorfenuron -N9phenylurea; CPPU) is the only small molecule compound known to affect septin filament assembly. FCF is a synthetic plant cytokinin that consists of a chlorinated pyridine and a phenol ring joined together by a urea group. FCF was fortuitously discovered to reversibly affect the localization and morphology of septins in the budding yeast Saccharomyces cerevisiae. Subsequent studies in mammalian cells and the filamentous fungus Ashbya gossypii showed that FCF dampens the dynamics of septin filaments, amplifying the length and thickness of septin filaments. Notably, FCF had a similar effect in a cell-free in vitro assay, boosting the assembly of purified recombinant septin complexes into higher order filamentous structures. While not ruling out the possibility of off-target effects in cells, these studies suggest that FCF has a direct effect on septin assembly. Understanding how FCF binds and affects septins can provide new insights into the mechanism of septin polymerization and guide the design of small molecule compounds that target septins with high specificity and affinity. Computational simulations of drug-target interactions using in silico molecular docking and molecular dynamics approaches are commonly used for the rational design and screening of drugs. As evidenced by the paucity of high-resolution atomiclevel septin structures, studying septin-FCF interactions by X-ray crystallography can be very challenging. To gain an insight into how FCF binds septins, we performed in silico simulations of FCF docking to all available high-resolution crystal structures of septins.