FIGURE 1.

A single point mutant, Q4A, phenocopies SEPT2 Δ15 filaments. A, alanine-scanning mutagenesis of first 15 amino-terminal residues in SEPT2. Mutations were made in full-length GFP-SEPT2 and transfected into HeLa cells. Scale bar indicates 8 μm. B, heterotypic mammalian septin complex (SEPT2-SEPT6-SEPT7-SEPT9) is an octamer with alternating NC and G interfaces. Each colored jellybean represents a different septin. The concave surface of the jellybean represent the NC interface, whereas the convex surface represents the G interface. SEPT2 interacts with itself at the NC interface within the octamer; however, it is a dimer at the G-interface in the absence of the other septins (top and middle row). SEPT2ΔN mutant forms filaments (bottom row).